FAQ

Table of Contents

Layout

• What can you tell me about the thread pitch on products with M3 thread?

  The M3 thread pitch used to secure encased SynQor modules is 0.5p. SynQor datasheets allow designers to purchase encased modules as either encased baseplate or encased with a non-threaded baseplate.  The encased baseplate version of the module always contains a threaded mounting provision.  The standard thread series for this module mounting option is always M3.  The complete thread description of this thread series typically requires the identification of the thread pitch.   SynQor’s standard implementation for M3 threads always uses a thread pitch of 0.5p. Any time “M3” is specified on a SynQor datasheet, the full thread series representation is defined as M3 x 0.5p.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   

• What type of thermal relief should I use?

  Significant performance improvement can be made by designing a printed circuit board to properly sink heat away from the converter through its pins. The first step is to ensure a correctly formed solder joint at each pin. A smooth fillet and complete barrel fill should be observed at the boundary of the pin and mounting hole to ensure maximum heat conduction from pin to board (as shown below).  In order to maximize heat transfer during the soldering process, i.e., to prevent the solder heat from sinking from the pin to the PCB inner layers, it may be necessary to incorporate a “spoke wheel” thermal relief pad design on the PTH inner layers, such as shown below.  It is worth noting here that SynQor encased and baseplated products are not compatible with reflow solder processes as it may cause damage to or compromise the converter’s internal solder joints.

  
  

   

  Ideal Solder Fillet Formation

  
  

  "Spoke Wheel" Inner Layer Pad Design

  
  The board itself should also have as many layers and as high of copper weight as is practical for the application. Large ground and power planes are best as the most heat will be conducted through the large power pins of the converter on both input and output sides. The heat must also have a path to conduct from the copper planes of the board to the outside environment. The typical FR4 material used in construction of a printed circuit board is greater than 1000 times less thermally conductive than copper and will act as an insulator between each copper plane. To mitigate this, generous use of thermal vias is recommended in the board area surrounding and below the converter. A proper density of vias allows heat to conduct from the board to the air while maintaining a large amount of copper area to conduct to the vias (refer to example below).
  
  

  Thermal Via Design Example
   

  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

• What can you tell me about sockets for PCB-mounted SynQor products?
  SynQor generally recommends that our board-mounted products be soldered into the system application board, as this makes the most reliable and highest performing electrical and thermal connection for deployed products.
  
  For system prototypes and temporary testing, sockets are a convenient way of connecting converters to test boards and fixtures, and SynQor does provide evaluation boards with socketed connections. 
  
  It is important to keep in mind that sockets are a poor thermal connection between a converter or similar product and the host printed circuit board (PCB), which can compromise the thermal performance of converters, particularly open-frame converters. This problem is further exacerbated by the fact that the socket connection has significant electrical resistance that causes additional heat to be dissipated. For accurate thermal evaluation, it is important to solder the pins to the host PCB, particularly when evaluating open-frame converters.
  
  If the shippable system design requires the use of sockets for assembly or maintenance, then we recommend that the socket be of a type that uses tin-plated contacts having sufficient contact normal force to make and maintain a gas-tight electrical connection. The system design should also limit movement of the pin-socket interface during thermal cycling or vibration conditions in the product service environment to prevent tin-fretting corrosion.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  
   

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Conducted EMI

• What is the best strategy to minimize EMI?

  There is no perfect EMI strategy for all applications, but some basic thoughts beforehand can make the task much easier. Meeting EMI performance specifications is ultimately a systems issue and will depend on more than just the specific filter elements and converters. For example, EMI performance will be affected by how the interconnect cables are routed, grounding architectures, the characteristics of the load electronics, and the use of EMI shielding and enclosures. Here are some tips that may help:

  1)    Select a SynQor filter that is appropriately rated for the converter’s maximum input current as stated in the datasheet. SynQor has a complete range of AC and DC line filters that are designed to work with SynQor converters. The filter’s attenuation profile is designed to attenuate noise at the switching frequency of the converters.  

  2)    Some systems will require additional external components to meet specific EMI requirements. For example:
          a.    Additional differential capacitors close to the converter's input and output terminals can help mitigate differential mode noise.  
          b.    Common mode capacitors or a common mode choke can help keep the CM current flows in check. Connecting the common mode capacitors through a low impedance path to ground can also be helpful. 
  3)    Make sure that the location of components minimizes noise.
          a.    Keep the output of the filter or converter away from the input cables to avoid high-frequency coupling.
          b.    The distance between the filter output terminals and the converter’s input terminals should be minimized.
          c.    De-coupling capacitors should be located as close as possible to the converter, especially X-caps and Y-caps.
  4)    Use wide ground planes to minimize radiated coupling. Use ground planes in the PCB to minimize differential conductors' loop area and impedances. Use best-proven engineering practices and guidelines for PCB design and cable routings to minimize the loop area of circuits carrying high-frequency currents.  
  5)    If possible, connect the baseplate to the chassis ground.  A solid ground plane helps contain the circulating CM currents in a more deterministic path.  
  
  Additional suggestions for DC-DC converters only:
  1)    For DC-DC converters, include an adequate input dampening network to avoid instability issues.  Note that SynQor filters include sufficient bulk damped capacitance, which allows for stable operation of most SynQor converters without any additional external components assuming the rating of the filter and converter are matched, the input voltage remains above 16Vdc (for 28 V applications), and no additional filtering components are present between the filter input pins and the source.
  2)    Connect the COM-OUT pin on DC line filters to the output return net of the converter. In some cases, this helps mitigate common mode emissions. The connection provides a low impedance path for some of the common mode currents to return to the source (DC-DC converter) through the filter. 
  
  Implementing all of these tips might not be necessary for a system to comply with a set of EMI requirements. It might be possible to meet the requirements with just a few of these suggestions. However, we typically recommend that customers leave placeholders for the components we have mentioned in their prototypes.  This will allow designers to quickly test various configurations and select which tips yield a better result.
  
  SynQor has an EMI application note that further details these principles and includes recommendations for one and 2-stage filters designed around SynQor's converters.  In addition, SynQor has an Input Stability Calculator which is intended to help the user select the proper components to insure stability of the system input stage.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What type of conducted line filter should I use?

  SynQor has a wide selection of AC and DC line filters that can help systems meet various EMI requirements when paired with compatible converters. Try to match the filter current and voltage rating with the converter's maximum input voltage and current rating. The filter's voltage and current rating can exceed the converter's maximum current rating. We do not advise using a filter that is underrated when compared to the converter input specifications. The attenuation characteristics of each filter have been designed to mitigate noise emissions for the same family of converters.  SynQor has tested various representative filter and converter modules from different MCOTS and Hi-Rel product families for EMI emissions at third-party external qualified facilities to demonstrate that our products can be used in systems that must meet some of the most stringent EMI requirements.
  
  Depending on the specific requirements, some additional filtering components may be necessary. After all, meeting EMI requirements is ultimately a system-level issue and will depend on more than just the specific filter elements and converters. For example, EMI performance will be affected by how the interconnect cables are routed, grounding architectures, the characteristics of the load electronics, and the use of EMI shielding and enclosures. 
  
  SynQor produces various filters and converters families, each designed for a specific industry.  This is because each industry’s requirements can be different. We suggest you select the filter and the converter according to your particular industry.  Mixing filters and converters from other product families is not advisable. 
  
  SynQor filters include sufficient bulk damped capacitance to allow a stable operation of most SynQor converters without external components, assuming the rating of the filter and converter are properly matched, the input voltage remains above 16Vdc (for 28 V applications), and no additional series filtering components are added between the converter input pins and the source. 
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• How do I choose Y-Caps?

  Y-caps, sometimes referred as EMI common mode capacitors, are typically connected between the input or output power feeds to chassis ground. Typically, these capacitors are added to a system to help mitigate common mode emissions.  In most cases, the value is generally finetuned empirically through bench tests. The capacitors are usually small ceramics in the order of a few pico-faradays.
  
  Y-capacitors connect between active circuits and chassis ground. These circuit nets can be at potential voltages significantly above the chassis potential, and a short in a Y capacitor can thus result in a shock hazard. As a result, there are a number of industry and military standards that place stringent electrical and mechanical requirements for these capacitors. The specific requirements that a Y capacitor meets should be listed in their data sheets. Selecting the correct Y capacitor for your system will thus depend on your specific system requirements. 
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What does the input filter of your converter look like?

  In general terms, most SynQor passive filters include common mode and differential mode filtering. The common-mode section includes common mode capacitors and a choke. The differential mode section is composed of various LC stages. The simplified topology for each filter can be found on page two of each filter’s datasheet. SynQor also offers multiple active transient 28Vdc filters that can help converters meet various spike and surge requirements and EMI requirements. 
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What if I don't have a chassis ground?

  Systems can operate without a chassis ground connection. Having and using a chassis ground is preferable whenever possible, but it is not mandatory. You do not have to connect any terminals in the filter or converter to chassis ground.  Note that AC and DC line filters typically include common mode capacitors and a chassis ground pin.  For these capacitors to be effective, the filter’s chassis ground pin should be connected to chassis ground through a low impedance path.  In the absence of chassis ground, you might have to add a common mode choke to impede the follow of some common mode currents.
  
  Encased converters include a baseplate that is electrically isolated from any input or output terminals in the module and all the converter’s internal components.  Even if the baseplate is isolated from all the components and pins, some unavoidable parasitic capacitances persist between some of the internal components and the baseplate.  These parasitic capacitances are very small. The EMI effects of these parasitic capacitances can be reduced by grounding the baseplate in certain situations.  However, grounding the baseplate is not required.  Depending on the application requirements, the baseplate can be connected to chassis ground or left floating with respect to ground. 
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What type of filter should I use for multiple converters?

  Multiple converters can be powered from a single filter if the maximum total combined input current ratings of the various converters do not exceed the current rating of the filter. The filter should be selected based on the maximum amount of current that all the converters can draw in a worst-case scenario.  A single filter module is often required when paralleling non-isolated converters or converters whose current share signals are referenced to the input return pin.  This avoids the degradation of common-mode attenuation characteristics in the filter. 
  
  Multiple SynQor converters in the same system may also use a single dedicated filter for each converter if the input terminals are not interconnected directly or indirectly by any control or load sharing signals referenced to the primary side. The filter’s voltage and current rating must be greater or equal to the converter's maximum input voltage and current rating, as shown in the datasheet’s electrical characteristics section.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• I currently have my input and output filtering arranged for a different manufacturer's converter. Will your module work with this filtering or must it be changed?

  Yes, SynQor’s modules could work if the attenuation characteristics of the filter are compatible with the switching frequency of the selected converters. However, even if the attenuation characteristics of the filter appear to be compatible with the converter, we would still advise that you verify the EMI performance of the entire system through bench tests. The filter’s attenuation profile might still allow some emissions from the SynQor converter back into the input rails.  Note that meeting EMI requirements is, after all, a system-level design issue.  The converter and filters are only part of the solution.
  
  In general, SynQor's converters tend to have better EMI performance than many other power converters available in the market because of the internal design. The baseplate is isolated from any of the input and output terminals or any of the internal components in the unit, as shown below. All the converter pins and the internal components are surrounded by thermal compound.  As a result, in many instances, SynQor converters have lower common mode noise emissions compared to other similar products in the market. 

  
  

  Internal Construction of an Encased Module

  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

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Radiated EMI

• How to design for radiated emissions?

  Meeting radiated emissions specifications requires designers to follow a system-level design approach. Meeting EMI requirements is ultimately a systems-level issue and will depend on factors specific to the application. These include, for example, grounding architecture, the characteristics of the source, the characteristics of the load, the use of EMI shielding, mechanical attachment of the power converter to the system frame, the characteristics of the input voltage source, and distribution cabling. EMI issues typically require a very hands-on approach when bench testing because every system is different.  Almost all aspects of a design can influence the EMI performance of a system. As a result, there is no single, standardized solution to this problem.  This is an issue that must be addressed at the system design level. 
   
  Most systems are able to meet radiated emissions requirements by first meeting conducted emissions, using good EMI layout practices and an EMI shield. Good conducted emissions performance is often required to meet radiated emissions requirements. This is because long conductors can be an important source of radiated emissions. In addition, design features like a metal enclosure and wide power and ground planes significantly attenuate electromagnetic emissions within the radiated frequency range.

   
  Tips on how to design your system:

   
  Radiated emissions can result from differential and common mode conducted noise emissions. Containing these types of conducted noise emissions within a system can help improve radiated emission performance of the entire system. To determine which of the two noise emission mechanisms is prevalent in a system, please consult the “How to discern differential mode from common mode conducted emissions” Frequently Asked Question in the Conducted Emissions section of our FAQs.

   
  Differential-Mode Radiated Emissions:

  Differential-mode noise typically radiates from small loop antennas within the system. Loop antennas can be defined as the area enclosed by a current-carrying loop. The magnitude of the field is proportional to the magnitude of the current, the enclosed area, and the square of the oscillating frequency. Reducing the area enclosed by any current loop can easily minimize differential-mode noise. Care has to be taken in the layout of all SynQor power modules to reduce differential mode radiation.

   
  Common-Mode Radiated Emissions:

  Common-mode radiation is harder to control and usually determines the overall radiated emission performance of the product. Common-mode radiation usually emanates from the input and output cables. Due to their relatively long length, input and output mains are unfortunately good transmitters of EMI noise. Input and output cables behave as monopole antennas driven by a voltage. Decoupling both input and output mains with ceramic capacitors to chassis ground close to the power module suppresses the excitation voltage. Care has to be taken not to exceed the leakage current requirement when adding capacitors from any point to chassis ground.

   
  EMI Shield:

  An EMI shield is an effective technique to suppress radiated emissions generated from any component in the system. Every component lead or trace can behave as a transmitting antenna as frequencies increase. Conductors, leads, etc., can become effective antennas as their physical dimension is equal to or greater than the ½ wavelength of the radiating noise. An EMI shield (a Faraday’s cage) can be placed around the noise-emitting components to suppress radiated emissions. The enclosure needs to be made from an electrically conductive material and needs to be grounded. Ideally, it needs to be free of holes and crevices (small gaps and crevices will allow noise emissions at higher frequencies to escape/radiate into the ambient).
  
  Any extended interfaces where two metal pieces meet can prevent the metal enclosure from suppressing radiated emissions. Generated noise with fields oriented parallel to the interfaced seam will easily circumvent the enclosure. To be an effective shield against radiated emissions, the two enclosure sections have to effectively make electrically conductive contact along the entire interface length. The shield performance can be improved by adding an EMI gasket between the two metal pieces.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• How to discern differential mode from common mode conducted emissions?
  A current probe and a spectrum analyzer or a current probe and a scope with FFT capabilities can be used to determine the nature of the conducted noise emissions that could be affecting a particular system.  In many cases, conducted differential and common mode emissions can be differentiated by comparing the emissions measurements obtained from a current probe where the two input or output power conductors run in parallel through the current probe as shown in figure 1, versus when one of the conductors is looped so that this conductor runs in the opposite direction from its counterpart (Figure 2). The difference between the noise levels obtained from these two tests can help provide insight into which of the two noise mechanisms is more prevalent in a particular system.
   
  Differential-Mode:
  Suppose the majority of the noise is differential in nature. In that case, the emissions obtained from the two conductors running parallel through the current probe will exhibit lower emissions (Figure 1) than when one of the conductors has been looped so that it runs in the opposite direction to its counterpart (Figure 2).
   
  Common-Mode:
  When these two tests are conducted, common-mode noise will exhibit the opposite behavior with respect to differential noise. If the emissions are primarily due to common-mode noise, the two conductors running in parallel will (Figure 1) exhibit higher emissions than when one of them has been lopped so that it runs in the opposite direction to its counterpart (Figure 2).
  
  
  Figure 1. Both conductors run in the same direction through the current probe.
  
  
  
  Figure 2. One conductor runs in the opposite direction than its counterpart through the current probe.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   

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Near-field EMI

• How will an open frame converter perform versus an encased converter?

  With few exceptions, most customers have found the near-field characteristics of SynQor's open frame converters to be no worse, and often better than the typical encased converter. SynQor has several suggestions for reducing near-field radiation –  the first of which is to place a ground shield beneath the converter. SynQor suggests placing a primary referenced ground shield beneath the converter's primary circuitry, and a secondary referenced ground shield beneath the converter's secondary side circuitry. The isolation barrier on all SynQor converters is easily found by looking for the 1.4mm clearance gap located on both the top and bottom of the PCB, or by locating the optoisolators which also identify the barrier. (Note: All of SynQor's magnetic assemblies are considered primary referenced.) With regard to the near-field EMI above the typical encased converter, a baseplate is not a perfect "shield" as commonly thought. Unfortunately, the baseplate is tightly coupled to the converter's high frequency switching nodes (in particular, the drains of the primary-side MOSFETs). The shield is therefore "bouncing" and attempts to stop it from doing so by grounding it to the output are challenging. Typically, the circuit path to ground is hindered by the parasitic inductance of the PCB connection. As such, the baseplate is not well-grounded at high frequencies, and radiates significant noise. There are also still the sides of the module to contend with, as these are not generally shielded. If there is sensitive circuitry, it is best not to place it directly over a converter or close to the edges of the converter unless it has a ground shield directly over or under the conduction path, as this will reduce any coupling. It is also helpful to note that the amount of noise that can be coupled is proportional to the cross sectional area of the conduction path; the smaller the loop, the less noise that will couple.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

• What about other Parasitic Baseplate Effects?

  If you could hold the baseplate quiet by grounding through a low inductance path, the result would be a great deal of common-mode current that would flow from the primary side switching nodes to the baseplate (through parasitic capacitors) and to the output ground. This then creates other problems that need to be addressed, mainly conducted common mode noise. Common mode noise tends to be a challenging problem to control. SynQor's converter design eliminates this problem as it has very little parasitic capacitance to the output ground. What noise it does have is effectively controlled with a common mode capacitor that we place on our converter. Compared to the industry standard Class B conducted noise filter, you will find that the SynQor converter needs half as many filter stages due to the reduced common mode noise. Also see SynQor's EMI application note.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

• What about magnetic fields?

  Encased converters will offer improved protection from near B-field radiation. At most frequencies, an encased converter will be approximately 10dB/uM more quiet than the open frame design. If B-field noise is a critical design consideration, any SynQor converter can be ordered with an optional baseplate, which will offer the same reduction in B-field noise.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

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Enable Circuits/Inrush Control

• Why do I need an inrush controller?

  A controller can reduce the inrush current when turning on a system. A high inrush current demand is typically an undesirable characteristic in most modern power systems. High inrush current through the input conductors can induce voltage spikes, can cause the voltage across the input lines to droop or even cause the source to temporarily shut-down if the source mistakes the high inrush event for a short circuit event. High current in the conductors means that you may need to increase the conductor size and use a higher rated fuse.  Voltage spikes can damage other equipment connected to the same bus.  A voltage droop in the input lines can cause other devices already operating on the same bus to draw more current, misbehave or even shutdown.  A shutdown of the source’s output will force all devices connected to the bus to shut-down and restart.  

  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

• How do I select an inrush controller?

  You can drive the enable of a DC-DC converter with the inrush controller's power good or enable signal provided there is no EMI filter between the controller's ground reference and the converter's ground reference. If there is an EMI filter located between the inrush controller and the enable circuit, the noise which the EMI filter rejects will appear on the enable lines, and could cause the modules to turn on and off randomly depending upon the size of the injected noise. The inrush controller and the converter must have the same reference. This can be avoided by leaving the modules permanently enabled, not using the Power Good signal, moving the common mode filter to come before the hot swap circuit, or adding some isolation between the Power Good output and the input to the modules (such as an optocoupler).

• How do I sequence multiple converters?

  Sequencing requirements need to be considered in the preliminary stages of the power supply design. Usually these requirements are driven by ASICs or processors, which have separate Core and I/O voltages. Often these voltage rails must turn on in a specific order (sequence) or are required to have no more than some maximum voltage difference between these rails. If this maximum difference is violated, the chip can be damaged or even destroyed. In general, there are three (3) ways to sequence the turn on characteristics of multiple converters.
  
  The first method is to turn the converters on in a specific sequence with either a control chip such as Summit Micro's SMH4804, or with discrete circuitry. A simple solution is to have the output of one converter drive an optoisolator that enables the second converter, and so on. In general most sequencing requirements will want the lowest voltage to turn on first, and off last. It is important to use an optoisolator to enable the other converter as the enable is a primary referenced signal, while the output of a converter is a low voltage isolated SELV signal. 
  
  Another method often used is to tie diodes between the different voltage rails in a manner that while powering up the diodes will conduct, but when the converter outputs are fully on, the diodes are reversed biased. For example, a diode between the 5V rail and the 3.3V rail, with the cathode connected to the 5V rail, will force the 5V rail to follow the 3.3V rail while turning on, but once the 5V rail is at 5V, the diode will be reversed biased. This forces the difference in voltage between the two rails to be no more than one diode drop apart. Conversely, 3 diodes with a 0.7V drop in series from the 5V rail towards the 3.3V rail will ensure that the 3.3V rail is charged should it come up after the 5V rail.
  
  The last and most complex solution is to place FETs in series with each converter's output, and enabling the FETs once the converters are fully turned on. By carefully controlling the turn on of the FET gates, the voltage rails can be brought up in strict adherence to any sequencing specification. Such a solution can be built with discrete components or by using a specific controller such as Summit Micro's SMT4004. One note of caution when implementing these solutions: if the sense lines are connected on the output side of the MOSFETs, the converter will not be able to sense its output voltage at turn on until the MOSFETs are on. This will cause the converter to raise its output until it reaches over voltage protection. You must either connect the sense lines directly to the converters output and trim up to compensate for the FETs on resistance, or add additional FETs to connect the sense lines after the main FETs are enabled.

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Component Selection

• How do I choose an input electrolytic capacitor (input E-cap)?

  SynQor has written an application note  on how to select an input electrolytic capacitor and why this capacitor is needed. In general, the stability issue arises from the fact that a regulated DC-DC converter is a constant power device – it maintains the output voltage at a fixed value as the input voltage is varied. Thus, as the input voltage increases, the converter acts to decrease the input current; and as the input voltage decreases, the converter acts to increase the input current to maintain constant output power.
  
  The result is that a DC-DC converter’s input impedance is characterized as an incrementally negative resistor (at frequencies below the bandwidth of its control system). Unless the converter is properly damped, it may oscillate and may cause damage to the converter.
  
  SynQor’s application note uses a simplified model of a filter/converter system to evaluate how system stability margins are affected by the addition of a simple R/C damping network. We also provide a Microsoft Excel spreadsheet that uses the stability criteria developed in this application note to help our customers design and optimize the damping necessary to ensure good stability margins in a specific application.  The application note and the calculator can be found here:
  
  Application Note: 
  Application Note link
  
  Input Stability Calculator: 
  Input Stability Calculator link
  
  SynQor’s DC EMI filters have damping networks integrated into their output stages.  However, in some applications the DC filter’s integrated damping network may need to be supplemented with external damping network to ensure system stability. Figure 1 shows all the relevant components whose values will be needed for an input stability analysis.
  

  Figure 1: Components to be considered for input stability analysis
   

  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

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General Application

• Can I create negative voltages with SynQor converters?

  SynQor's isolated converters can be used to supply negative output voltage to the load. Simply connect the Vout+ terminal to the system output ground, and a negative voltage will be generated on the Vout- terminal.
  
  SynQor’s non-isolated converters can also be configured to achieve a negative output from a positive input as described in their datasheet.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

• How do I read the codes on the product label?

  Each product has a label which reveals the product part number, revision character code and serial number for that module. This information can be found on the label in the specific locations detailed in the photo shown below.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

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Safety

• Where do I find the safety certifications and the conditions of acceptability?
  All safety certifications, including the Conditions Of Acceptability, can be downloaded in PDF format from Our Quality & Compliance Standards page.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
• How do I choose a fuse?

  SynQor's product datasheets specify the recommended fast blow external fuse to be used.  Additionally, the Conditions Of Acceptability (COA) section of the Safety Certification details the type of fuse required for each converter. 

  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

   

• What is creepage and clearance?

  Creepage and Clearance form part of the product’s electrical insulation system that protects the user from a risk of shock. Creepage distance is the shortest distance along the surface of an insulating material between two conductive parts. Clearance is the shortest distance in air between two conductive parts.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What is "insulation rating" and "isolation rating"?

  ulation refers to the design parameters used to isolate the primary side signals from the secondary side signals. This covers the specifications for Creepage and Clearance between traces and components, as well as the type of insulation used in the transformers. The transformers transfer energy between the primary (Input) and secondary (Output) stages of the converter. Isolation refers to the breakdown rating of the isolation stage, either in the transformer or between isolated components such as optoisolators. SynQor tests and guarantees that all converters are capable of withstanding the minimum voltage breakdown specified on the product datasheet.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• Are any dangerous voltages exposed on the surface of the converter?

  InsIn the United States, UL defines an "Unsafe" voltage as 60 V. At input voltages of 0 to 60 V, the highest voltage will be across the midbus capacitors, this is an AC signal, operating at the switching frequency, with a maximum peak to peak amplitude of about 58 V. Above a DC input of 60 V the maximum voltage is the input voltage across the primary switching FETS, which is approximately Vin plus a few volts.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• Are the existing en 60950-1 product safety certifications still valid now that en 62368-1 has become effective?
  The existing EN 60950-1 Product Safety certifications are still valid; however, only to the EN 60950-1 Product Safety Standard.  The end use customer must determine when EN 62386-1 Product Safety Certification is required.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

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Performance

• How do I reduce output noise and ripple?

  In general, SynQor's converters have significantly lower output noise and ripple when compared to traditional isolated converters. This is due to SynQor's patented power topology, and excellent design practices. Filtering typically helps reduce the output voltage ripple provided that the filter is designed to attenuate the main frequency components of the ripple. The simplest filter is a differential capacitor across the output of the converters. We typically recommend to customers to empirically try various capacitors at the output of the converter to meet their specific requirements. The reason we recommend that you try different capacitance values empirically is because the effective attenuation that can be provided by a filter capacitor will depend on the output impedance of the converter and load distribution network in addition to the parasitic inductance and resistance of the filter capacitor. In the diagram shown below in Figure 1, Zout is the output impedance of the converter, Ldis and Rdis are the parasitic impedances of the output voltage distribution network and C1, ESR and ESL are the parasitic impedances of the additional filter capacitors.
  
  
  Figure 1. Converter Output Elements impacting output ripple.
  
  The actual attenuation that can be achieved will be dependent on the layout and interconnect impedances and thus ultimately dependent on the details of the customer’s specific implementation.
  
  However, we can provide some general guidance for managing the output voltage ripple. We generally encourage our customers with critical output voltage ripple requirements to design their first boards with as much filtering as possible. Please make sure that you do not exceed the maximum output capacitance as specified in the datasheet. It is fairly simple to remove (or bypass) filter elements; it is much more difficult to add them if what you have is insufficient.
  
  1. If you are restricted to only using capacitors, then we suggest starting with one of SynQor’s evaluation boards, then you measure output ripple and add capacitors until you are able to meet your system requirements. The available evaluation boards are listed in our selection guide on our web: Evaluation Board Selection Guide. We recommend the following approach for board layout:
  
           a.    Use surface mount X7R ceramic capacitors. They have comparatively low ESL/ESR characteristics and superior temperature properties (compared to other ceramic technologies and packages).
           b.    Position these capacitors close to the pins of the module.
           c.    Route your output copper so that the output current is forced to flow as close to the terminals of these filter capacitors as is practical.
  
  2.    If you have the space, you may want to consider adding an output filter inductor. Note – if you do this, we recommend that you connect the sense leads between the output of the converter and the input to the inductor as shown in Figure 1. If you put the sense leads on the load side of the filter inductor, you are introducing a new pole/zero into the plant and will affect the system stability margins. We have copied a simple spreadsheet example below in Figure 2 to show you how we go about calculating the value of an effective and well damped filter network. Please refer to Figure 2 below for a methodology for designing an effective L/C filter to reduce output ripple of 500mV to 50mV. 
  
  
  
  
  

  Figure 2. Suggested LC filter to reduce output ripple for NQ60W60HGx40 converter operating at the same input and output voltage of 28 Vdc (as an example).​

  
  3.    Finally, measuring output ripple can be challenging. Please refer to the “Output Voltage Ripple Measurements” section below for more information.
  
  
  Output Voltage Ripple Measurements
  It is first important to determine if the excessive noise you are measuring is real and not reflected or common mode noise due to the test setup. How you measure noise is critical to determining whether the level is acceptable or if more filtering is required. SynQor has an application note that addresses this issue in detail: http://www.synqor.com/documents/appnotes/appnt_Vout_Ripple_Measurement.pdf.
   
  We performed comparison tests to measure output noise using three techniques.
           I.    The first technique used a regular scope probe with a ground wire.
           II.    The second technique used a BNC connected to the output voltage measurement point (unterminated) on an evaluation board.
           III.    The third technique used a BNC cable cut at the power supply end with the braid soldered to the output return of the converter and a 50 ohm resistor from the positive lead to the Vout+ of the power converter.
  Noise levels ranged from approximately 1 V (using the first technique) to 20 mV (using the third technique). Note how broadly results can vary depending on how the noise is measured.
  
  We recommend, of course, using method number III. But whichever approach you take, it is important to verify that your measurement system is accurate. A simple, but effective test of a measurement system is to take the positive end of the measurement device and the return end of the measurement device, short them together and place them on the output return of the power converter. If you see anything on the scope, then there are problems in your measurement system. Normally, your measurement should yield a zero voltage reading.
   
  An output voltage ripple measurement is only meaningful if the impedance of the load network is well defined. We have specified in our datasheets the actual output capacitors that were used for measuring the datasheet specified output voltage ripple. We could have used different output capacitances, but the parallel combination of capacitors shown in figure 3 that we used for our output ripple measurements represents a ‘typical’ application (based on our experience applying our products in many different types of applications).
  
  

  Figure 3. Output impedance used to characterize output voltage ripple for the NQ60W60HG (as an example).

  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

• How much output capacitance can I drive with your converter?
  All SynQor datasheets specify the maximum allowable output capacitance to allow a normal startup at rated output load. If the output load current at startup is reduced, then a larger amount of capacitance than defined in the datasheet is possible.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  
• How do you trim a converter?
  All SynQor converters have a trim pin, which allows trimming the nominal output voltage higher and lower. In general, to trim a converter low, a resistor is connected from the trim pin to the -Sense pin. To trim up, connect a resistor from the trim pin to the +Sense pin. The value for the resistor is calculated with the formulas provided in the converter's datasheets. You can also use our Trim Resistor Calculator. The trim formulas match accepted industry standards for full, half, quarter and eighth bricks.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   
• Can I trim a converter actively?
  Adjusting the output voltage or “trimming” the output of converters with an external active circuit is possible but the rate of change should be slow compared to the bandwidth of the converter to avoid stability issues.
   
  The output voltage of converters equipped with the trim function can be dynamically controlled through something like a Digital to Analog Converter (DAC). Some converters offer plots in their datasheets of the output voltage as a function of the voltage at the trim pin with respect to the Sense- pin. If the plot is not available, you can use the Trim Calculator to build the plot by selecting various output voltages. For example, a graph for the MCOTS-C-48-28-HZ  whose datasheet does not have a plot can be created simply by using the Trim calculator (Figure 1).
   
  Note that each incremental/decremental change in the set output voltage would need to be made fairly slowly.  For this particular converter, each change should be made once every couple of hundreds of milliseconds. This will help you avoid instability issues. We do not recommend changing the output dynamically near the control loop’s bandwidth as this could lead to system stability issues. We also suggest that the output voltage trim implementation should be thoroughly tested in the lab for acceptable performance.
  
  

  Figure 1: MCOTS-C-48-28-HZ Trim Graph using Voltage Source

  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   
• How does Over Voltage Protection (OVP) work; does it track the trim?

  SynQor's Over Voltage Protection (OVP) threshold is fixed and does not get adjusted to any output voltage trim adjustments. Customers should use care when trimming the converter to ensure the OVP is not activated during transient conditions, or when series diodes or FETs are used on the converter's output. To avoid engaging the OVP protection feature when the output voltage set value is near the OVP threshold, a better alternative is sometimes to select a converter with the next higher nominal output voltage and then trimming down the output voltage to the desired value.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   

• Can I put converters in series?

  The outputs of SynQor's isolated converters can be placed in series; however, should one converter turn off, a protection mechanism should be implemented to ensure that the other converter is disabled as well.
   
  The isolated converters have been fully characterized in systems that subject the units to a working voltage equal to the maximum rated output voltage from any input to output pin. In a stacking application (converter’s outputs set in a series configuration), the converters may experience higher working voltage than the working voltage used to characterize the converter.  While we expect the product to work in most applications that exceed this working voltage, we cannot fully endorse it based on our design characterization data and product qualification testing.  The product also has not been characterized to be used with outputs connected in series.   Although we expect the product to work in this configuration, characterization and verification of the system must be done empirically by the customer.
   
  In addition to the working voltage issues already discussed, there are also considerations that pertain to how the system will behave through transient conditions. Typically, many of the issues we have outlined below should not damage the modules or the system. However, they may give rise to behaviour that is different than documented in our datasheets.

  • We recommend balancing resistors in parallel with each output to ensure an organized power down when the system is turned off.
  • We recommend diodes between the power output pins. If one of the modules turns off for any reason, the load current will flow through this device (as opposed to being forced to flow in the body diodes of the synchronous MOSFET rectifier internal to the DC-DC converter).
  • The start-up of the converters connected in series is controlled by the state of the ON/OFF pin of the converters. We recommend that you enable the stacked converters “ON” simultaneously to facilitate a smooth start-up of the output bus.
    • Current limit behaviour will be complex, particularly if a DC-DC converter goes into auto-restart when they are in deep current limit:
      • During an over current event, one module will go into current limit first. When its output voltage droops sufficiently, the unit will go into an auto-restart mode of operation while other units in the stack-up (with higher current limit set points) will continue to function.
      • The output current in the module that is in auto-restart will flow in the external diode. If the system remains in this mode, these diodes need to be sized to handle the load current.
    • The maximum capacitance specification applies to each individual converter connected in series.

  In general, any control feature that causes the converter to shut down may produce a behaviour not described in our datasheet (for example, over temperature faults).  It is not expected that this behaviour should damage either the modules or the system, but it will vary from the description provided in our datasheet.
   
  Please reference SynQor’s application note below for more information regarding the stacking of converters: Series Operation.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What are sense lines? Do I need to connect them?

  Sense lines are used to compensate for resistive drops along the power distribution path. The sense lines should be connected at the point of load or connected to the output pins of the converter. If the sense lines are not connected, the regulation and set point specifications contained in the datasheet will not be met. The output voltage might be slightly higher than the nominal voltage. No damage will occur if the sense lines are left unconnected. If an inductor is placed between the converter output pins and the load, the sense lines should be connected to the forward and return lines before the filter to avoid the creation of an additional pole in the control loop that could cause instability issues.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  

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Full Feature Converters

• What is the OR-FET signal used for?

  The primary function of the full feature converters OR-FET signal is to supply a voltage source higher than the converter's output voltage which can provide current to turn on the gate of an N-Channel "ORing" MOSFET. The signal has no implied "intelligence". ORing FETs are used to isolate the output of a converter in the event that the converter's output experiences a short fault. This is preferable to "ORing" diodes that have significant power losses at high output currents. This signal is very low power, and is not capable of supplying more than 50mW of power. Any control circuitry drawing beyond 50mW of power should be driven off the converter's main output.
  
  The OR-FET pin can also be used as a Power Good signal: when the converter is operating properly the OR-FET voltage will be much higher than the converters output, providing a positive indicator of a converter's health even in a system where converters are directly connected in parallel. More details are available in our Full Feature Application Note.

• Can I use the Cshare pin as an output current monitor?

  The current share pin will give a voltage that is proportional to the output current, but only for a single module. If two converters are sharing a common load by using the current share connection, the voltage will represent the average current of the two converters. This signal is referenced to the primary side of the converter, so to interface with a controller the signal will have to be brought across the isolation barrier through an optoisolator (unless of course the controller is on the primary side, then a direct interface is possible.) Any load impedance added to the CSHARE signal should be above 100kOhms. Loading on this signal will affect the current sharing performance. More details are available in our Full Feature Application Note.

• How do I synchronize modules?

  SynQor Full Feature converters have a pin to provide synchronization with an external clock. The signal should be a 5V TTL level rectangular wave with a duty cycle between 25% and 75%. The CSYNC signal is referenced to the Vin- pin of the converter. When synchronizing different output voltage converters, you should select the highest frequency specified for any converter as the common frequency. Converters will not synchronize properly at frequencies below that specified in their datasheet. More details are available in our Full Feature Application Note.

• Should I synchronize modules?

  While synchronizing converters may make EMI characterization and filter design simpler, it can also cause converter harmonics to stack on top of each other, creating a more difficult EMI problem to solve. Generally, EMI specifications require measurements be quasi-peak, and it is more beneficial to leave the converters not synchronized. Certain systems require synchronization so that the output ripple is at a single frequency. Applications such as wireless communications equipment, systems with extremely fast clocks, or sensitive optical circuits may find that the benefits of synchronizing the converters output ripple outweigh the EMI benefits of having un-synchronized converters. More details are available in our Full Feature Application Note.

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Parallel Converters

• Can I parallel converters for more power?

   SynQor's family of Kilo, Mega, Giga, Tera and some Peta half bricks can be ordered with the full feature set which allows converters to be paralleled for more power, as well as to take advantage of additional control features.

• How do I connect SynQor's full feature converters in parallel?

  To connect full feature modules in parallel, you simply connect the current share pins and the start sync pins of the sharing converters together. In addition, make sure that the Vin+ and the Vin- pins are tied together, as the Vin- pins provide a common reference for the current share signal. Outputs should be connected together at a common point with the sense lines. SynQor has an application schematic detailing these connections. Please refer to the Full Feature Application Note for this schematic.

• How do I trim converters in parallel?

  A trim circuit should be supplied for each individual converter, therefore each converter should have a trim resistor. Make sure that all trim resistors are the same value.

• Where do I connect the sense lines for parallel converters?

  The sense lines of converters in parallel should be connected together at the exact same point for balanced transient responses and the best output voltage regulation.

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Handling

• How should I store and handle open frame converters?
  Open frame converters can be damaged from poor handling, excessive mechanical shock, or from a static electric discharge. The units should be:

  • Carefully handled and not subjected to mechanical stresses
  • Treated as an ESD sensitive component
  • Stored in a static protective container which physically protects the converter
  • The converters should not be stored in plastic bags, or stacked on top of one another in any way
• Are SynQor's converters water wash compatible?

  Please visit our Aqueous Cleaning and Soldering Considerations Application Note for SynQor's open-frame, fully encased, and baseplated products.  

  If you still require support after reading the Application Note, please contact our Technical Support team to obtain help with your particular system. 

• What type of flux do you use?

  SynQor uses flux systems that meet or exceed Telcordia GR-78 CORE SIR and Electromigration requirements.

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Reliability

• What is SynQor's MTBF?
  SynQor's standard reliability metric is Mean Time Between Failure (MTBF) calculated in hours of operation. SynQor uses the Military MIL-HDBK-217F standard as well as the Telcordia TR-NWT-000332 standard to calculate MTBF based on ambient temperature and load. SynQor's standard calculations are for nominal input. Open frame modules are calculated at 80% load, 40°C and 300 LFM. Encased modules MTBF is calculated at a baseplate temperature of 70°C, while systems are calculated at 25°C. Calculated MTBF is listed in the product datasheet.
  
  In addition, SynQor also measures Demonstrated Field Reliability in MTBF which is based on actual Field Returns data compiled from customer product returns for failure analysis. To request any of this reliability information please contact our Technical Support team to obtain help with your particular system.
• What are common failure modes?

  The most common failure modes for converters returned by our customers for failure analysis is “No Fault Found” (NFF) and “Customer Induced Failure.”   SynQor has developed evaluation boards which may be purchased to allow customers to test and debug the operation of the converter before considering returning the converter to SynQor.  
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.

• How does synqor's product development and qualification process contribute to product reliability?
  SynQor has a three-stage product release process: POD, POM, and Product Qualification. SynQor requires that each stage must be completed and approved before the product can advance to the next release stage.  Strict adherence to this policy has contributed to SynQor’s proven track record of industry leading product performance and demonstrated product reliability.
  The first stage, POD, or Proof of Design, is the process during which the product’s performance is evaluated and characterized over all rated operating conditions and beyond, in accordance with HALT principles. POD testing measures component stresses to ensure that electrical design requirements are met and that no components are over-stressed under both normal and abnormal operating conditions. POD ensures that long-term reliability and life targets are achieved. Other tests performed at the POD stage include phase and stability margins, thermal margin, capacitive load tests, destructive thermal cycling, and waveform analysis.
  
  POM, or Proof of Manufacturing, ensures that SynQor has designed a product that can be manufactured per SynQor’s DFM (design for manufacturability) requirements with proper margins to be manufactured in a high volume factory. POM stage completion ensures that all required manufacturing and test equipment and processes are released and optimized for volume production, that target manufacturing and test yields are met, and that the product meets or exceeds SynQor’s product reliability requirements. Statistical Process Control (SPC) data and resulting process CpKs (process capability indices) are scrutinized to ensure that SynQor has a repeatable and consistent process.
  
  Product Qualification is the final stage of product release. The purpose of the qualification process is to ensure that SynQor has designed and built a product that exceeds both SynQor’s and our customers' expectations. Testing at this stage is conducted to relevant Mil-STD-810 requirements and includes exposure to thermal shock, extended high temperature life and humidity, mechanical vibration and shock, and full IPC-A-610 workmanship and mechanical and dimensional compliance.  Additionally, a thorough examination of electrical functional test data collected after each testing phase is conducted to identify any signs of drift or deviation as a result of the qualification test exposures.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.
   

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Troubleshooting

• How do I measure output ripple?

  Measuring output ripple and noise is extremely dependent on the test setup. A good starting point for this is to use SynQor's Evaluation Board which can be purchased from SynQor. Our evaluation board provides a BNC connector for measuring output ripple. The industry standard noise measurement requires 20MHz bandwidth limit which is detailed in our data sheets. There is also an application note titled, "Output Voltage Ripple Measurements," which provides proper methodology and test set-ups to achieve accurate output ripple readings whether you are using our evaluation board or an application board.
  
  This paper also describes how using a traditional probe with a ground clip will allow radiated noise to couple into the probe creating a false measurement, which manifests as large high frequency spikes. These are largely measurement artifacts which are most often caused by two effects: magnetic coupling through a large scope ground loop, and/or transmission line effects on unterminated cables. SynQor's application note on this topic will show you how to reduce the measurement circuit loop to a minimum, almost eliminating magnetic noise pickup and allowing a more accurate measurement of the converter's output voltage ripple.

• How do I measure Output Load Current?

  You can easily measure the output load current of any SynQor open frame converter. The application note "Output Load Current Calculations" outlines the equations and other information needed to make this measurement.

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Thermal

• How do I choose a heatsink?
  Choosing a heatsink requires knowing several things:

  • The output power required.
  • The power dissipated by the converter.
  • The worst case ambient temperature.
  • The maximum baseplate temperature of the converter, which is typically 100°C for most SynQor baseplated converters.
  • The type of module.

  Typically, to select a heatsink you need the thermal resistance of the modules.  The thermal resistance of the selected heatsink should be below that of the module. Note that increasing the flow rate of the cooling medium over the heatsink typically decreases the thermal resistance of the heatsink.
  
  To calculate the thermal resistance, you need the maximum allowable baseplate temperature, the ambient air temperature and the power dissipation.
   

  R_THBA = (T_baseplate – T_ambient )/ Power dissipation

  
  For most MilQor, AeroQor, RailQor, InQor, and CFQor products, the maximum allowable baseplate temperature is 100°C.  Hi-Rel parts can operate at case temperatures of 125°C. Note that the maximum output power for some specific modules becomes limited at temperatures near 100°C.  In this case, thermal derating of output power needs to be taken into account.
  
  Baseplate converters are designed to dissipate all the heat produced by the internal components of the converter through the baseplate.  The heat producing components are in close proximity to the baseplate.  Thermal compound used for encapsulating the converter components uniformly transfers heat from these heat producing components to the baseplate.  The baseplate temperature is uniform across its surface (Figure 1). The enclosure for the MilQor, AeroQor, RailQor, InQor and CFQor products is not designed to facilitate heat transfer away from any component. You should assume that heat transfer only happens between the baseplate and the attached heat sink interface.  The actual baseplate temperature will be a function of the properties of the heatsink and the cooling method utilized to cool the heatsink. 
   

  Figure 1: Temperature profile of a baseplated module.

  
  Example:
  Let’s determine the thermal resistance for the MCOTS-C-270-28-FT.  Figure 2 shows the expected thermal derating of the module as a function of baseplate temperature. Let’s assume we wish to operate the unit at full load.  Figure 2 states that the maximum baseplate temperature is 83°C if you wish to deliver full power. As long as you keep the baseplate temperature below 83°C, the units should be able to deliver full power. If you wish the units to run at baseplate temperatures above 83°C, you will need to decrease the output power of the system per Figure 2.
  
  Let’s assume we wish to design the cooling solution for the worst possible condition.  Figure 3 shows the maximum heat dissipation which occurs when the unit is running at full load at an input voltage of 425 Vdc.  Under these conditions, the unit requires the cooling solution to dissipate 63 W.  However, Figure 3 goes to a baseplate temperature of 25°C. For this analysis, the heat dissipation at 83°C is required. We need to compensate for the additional losses incurred by the module when operating at higher temperatures.
  
  Figure 4 shows the heat dissipation of the module as a function of baseplate temperature when running to 60% load.  We see that between 25°C and 83°C there is approximately 3 W of heat dissipation increase. The total estimated heat dissipation for the module can be approximated to be heat dissipation at 25°C at full load plus the increase between 25°C and 83°C which adds up to 65 W (62 W + 3 W).
  
  The thermal resistance can now be calculated:

  R_THBA = (83°C – T_ambient )/ 65 W
   

  Let’s assume the ambient temperature is 55°C. The thermal resistance value becomes: 

  R_THBA = (83°C – 55°C )/ 65 W = 0.43 °C/W

   

  Figure 2. (Figure 5 in the MCOTS-C-270-28-FT datasheet): Maximum output current vs. baseplate temperature (nominal output voltage).

   

  Figure 3. (Figure 3 in the MCOTS-C-270-28-FT datasheet): Power dissipation at nominal output voltage vs. load current for minimum, nominal, and maximum input voltage at Tbaseplate=25°C.

   

  Figure 4. (Figure 4 in the MCOTS-C-270-28-FT datasheet): Power dissipation at nominal output voltage and 60% rated power vs. baseplate temperature for minimum, nominal, and maximum input voltage.

  
  
  Let’s assume that you have decided to place thermal compound between the converter baseplate and the heatsink to improve thermal conduction. There-O-Link thermal compound resistance is: °C/W/ in² = 0.19. 

  Area of the heatsink of the Full Brick 2.486” x  4.686” = 11.65 in²   
  Thermal compound resistance = 0.19 in² °C/W / 11.65 in² = 0.016 °C/W

   
  Heatsink thermal resistance < (83°C - 55°C)/65W - 0.016 °C/W = 0.41 °C/W
   
  Let’s assume there is a heatsink with the following thermal resistance characteristics.  The thermal resistance chart in figure 5 show that the sample heatsink could provide appropriate cooling if the ambient temperature is kept below 55°C and the air flow is above 300ft/min.
                 

  Figure 5. Thermal resistance table of sample heatsinks.

  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.
   
• How does SynQor's thermal protection work, and where is the sensor?

  Heat sensors on SynQor converters are typically located near components that would commonly run at higher temperatures than the rest of the components. However, note that some SynQor converters, particularly the smaller ones, use the sensor in the micro-processor to sense the temperature in the module.  When the sensed temperature exceeds the over temperature threshold, the unit will shut down its output.  The output will automatically re-engage when the sensed temperature drops below the over temperature value minus the restart hysteresis value.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.

• What is the optimal orientation of the converter?

  In general, half bricks are less sensitive to orientation than quarter bricks. For half brick converters 2.5V and below, it is best to have the air flowing towards the output terminals; for half bricks 3.3V and above, it is better to have the airflow towards the input side of the converter. On quarter bricks and eighth bricks, it is always best to make the airflow perpendicular to the long side of the converter as this exposes the maximum surface area to a cooling airflow. Although the differences are minor, it is best practice to review the derating curves and thermal images found in the datasheets to determine optimal orientation.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• What is the difference in air speed measurements of CFM vs. LFM?

  Designers often need air speed measurements to calculate thermal derating and power dissipation for their DC-DC converters and for their overall systems. There are two basic units of measure: CFM (cubic feet/minute) is a measurement of volume, LFM (linear feet/minute) is a measurement of velocity. Fan manufacturers use CFM because they rate their fans according to the quantity of air they can move. Velocity (speed) is more meaningful to heat removal at the board level. This is what most DC-DC converter manufacturers will specify when calculating thermal derating curves and other performance specifications.
  
  To convert CFM measurements to LFM, use the following equation:
  LFM = CFM/AREA
  LFM = Linear feet per minute of airflow
  CFM = Cubic feet per minute of air volume
  AREA = the area of the opening in square feet.
  
  For example, let's assume you are blowing air through a 6" x 6" opening across the top of a DC-DC converter with a 100CFM, unobstructed fan. 
  LFM = 100/ 0.25 sq feet or about 400LFM calculated.
  
  The most accurate way to measure actual air speed is with an anemometer.
  Some manufacturers specify airflow in Linear Meters/Second. Use the table below to convert feet/minute into meters/second:
  100 f/m = 0.5 m/s
  200 f/m = 1.0 m/s
  300 f/m = 1.5 m/s
  400 f/m = 2.0 m/s
  500 f/m = 2.5 m/s
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

• How do I attach heatsinks?

  All SynQor threaded modules employ M3 screws. Use M3 screws with a length no longer than 0.125". Tighten the screws to a torque of 6.0 in-lb. Minimum screw length is 0.10" for adequate hold. Typically, you should add an interface material to aid in the efficient conduction of heat from the baseplate to the heatsink. The interface material could be thermal compound paste or a thermal pad.  
  
  Typically, holes are drilled onto the heatsink.  The fastening screws secure the heatsink onto the module through the threaded stubs.  The converter is then soldered on to the PCB.  Note that the module pins are not designed to manage any type of dynamic or static loading.  If the modules are to be subjected to vibration or shock, we suggest that you use additional fastening devices to secure the PCB onto the heatsink.  This type of assembly will minimize any stress on the converter pins.
   

  Figure 1. Assembly of a heatsink onto an encased converter.

  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 

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UPS

• What are the requirements for shipment of UPS battery packs and EBM systems?
  UPS battery packs must be shipped per Federal DOT Regulations as a Class 9 Fully Regulated Hazardous Material.  The battery pack must not be installed in the UPS when being shipped.  Note that a UPS may be shipped using standard shipping methods if it does not contain a battery pack. 
   
  SynQor prefers that the customer use SynQor’s Approved Battery Pack packaging, as this has been tested and certified to provide adequate protection for the product.  The customer may use their own packaging provided that the following UN and DOT Requirements are met (note that the customer is responsible for damage incurred due to improper or inadequate packaging):
   
  •    A UN certified carton must be used. UN markings on the carton must be appropriate for the lithium ion battery, i.e. UN certified for solids, that the package limitation in kilograms is equal to or greater than the total package weight (weight of contents and weight of packaging combined) and that the package type is either           X or Y.
  
  •    The battery pack must be packed in an inner packaging (re-sealable plastic bag is preferred) and packed in a way that will prevent short circuit and also prevent shifting inside the box during transit.
   
  •    U.S. domestic ground shipments of the 1U battery – 266 watt hours
  Ship as a medium lithium ion battery (>100 watt hours <300 watt hours)
  
  
  
  •    U.S. and Canada ground shipments of the 2U & EBM batteries
  Must be shipped Fully Regulated as they exceed 300 watt hours
  
  
  
  •    Air shipments (U.S. and International) of the 1U, 2U & EBM batteries 
  Must be shipped Fully Regulated as they exceed 100 watt hours
  
  
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  
• What are the weight specs for SynQor's Lithium Battery Packs?
  Standard 1U BAT-0200 Battery Pack:

  • The 1U standard battery pack weighs 10lbs. and provides 200 Whr. of energy.
  • In the standard 1U battery pack, there are 24 cells.  The total weight of just the cells is ~4.45lbs. 
  • The total equivalent lithium content weight is 24 cells x 3.2 Ah x 0.3g/Ah = 23.04g or ~0.05 lbs.

   
   Extended 2U BAT-0500 Battery Pack:

  • The 2U extended battery pack weighs 21lbs. and provides 500 Whr. of energy.
  • In the extended 2U battery pack, there are 56 cells.  The total weight of just the cells is ~10.35 lbs. 
  • The total equivalent lithium content weight is 56 cells x 3.2 Ah x 0.3g/Ah = 53.76g or ~0.12 lbs.

   
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  
• Who do I contact if I have a hazardous material emergency with a UPS battery pack or an EBM system?
  SynQor is enrolled in a 24 hour / 7 day per week emergency response service administered by Chemtrec.  In an emergency, please call the appropriate CHEMTREC Primary Phone Number listed for your region as noted on the Chemtrec In-Country Dial Number Master Form found under the following link: Chemtrec In-Country Dial Number Master Form.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.  
• How can I dispose of my SynQor UPS lithium-polymer battery pack or EBM system?
  SynQor UPS lithium-polymer battery packs as well as the SynQor EMB System shall not be returned to SynQor for disposal.  The customer is required to engage with their appropriate local authorities to determine the proper disposal process for these items. 
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
• Can I run SynQor rack-based system products inside a transit case?
  SynQor rack-based system products can be run inside a transit case assuming both front and back covers are removed (Figure 1), the air inlet temperature is within the operating range of the unit, and there is sufficient space between the front (inlet) and the back (exhaust) of the transit case to allow fresh air to flow through the unit. If the covers are closed, as shown in Figure 2, the temperature of the air inside the case will be recycled over and over, each time getting hotter until the point where the air temperature exceeds the maximum air inlet operating temperature. At this point, the unit could shut down due to over-temperature.
   
  
  Figure 1: SynQor transit case with both front and back covers removed.
  
  
  Figure 2: SynQor transit case with both covers closed.
  
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   

VPX

• WHEN DOES THE FAIL SIGNAL PULL LOW IN SYNQOR’S VPX MODULES?
  When the VPX experiences over-current, over-voltage and/or over-temperature protection, the FAIL* signal will trigger due to one of the output rails shutting down. The FAIL* signal notifies the user that one of the output rails is outside its specified range. In order to identify which output rail is outside the specified range, the I²C interface would need to be used to query the output voltage of each rail. The I²C will also allow you to monitor the input/output current and temperature of the VPX.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   
• WHAT TYPE OF CONFORMAL COATING DOES THE SYNQOR VPX USE?
  The conformal coating used on our VPX products is Parylene-C.  Please take note that the conformal coating is optional for most of our VPX products.  To choose the conformal coating option, select the “Y2: Conformal Coating” option “C”.

   

  Ex. VPX-3U-DC28P-001-MC2
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
   
• IS IT POSSIBLE TO MONITOR THE FAIL SIGNAL VIA I2C?
  Yes, but it must be done indirectly. The status of the FAIL* signal cannot be monitored using a single command through the I²C.  This signal is meant to warn the hardware that one of the outputs of the unit is out of range. In order to determine the status of the FAIL* signal, you must check the output voltage of each of the output rails through the I²C interface.  If one of the output voltages is out of range, the signal would be low; otherwise, the status of the signal would be in a tri-state condition (if not pulled high). The FAIL* signal does not provide you with the exact output that is out of range.  The I²C must be used to query the status of all the outputs of the VPX to determine which output is out of range.
  
  Additional Information
  Our VPX products are compatible with PMBus and IPMI interfaces. With I²C capability, you can query input voltage, current and power status; output voltage for each output rails; output current and power status for VS1, VS2 and VS3 outputs and three temperature readings at each card edge and middle of the VPX chassis. We would like to direct you to our VPX 3U I²C Operator’s Guide and/or VPX 6U I²C Operator’s Guide located on our website which dive into more details on the VPX’s I²C capabilities using both interfaces.
   
  If you still require support, please contact our Technical Support team to obtain help with your particular system. 
• WHAT I2C INTERFACE DOES THE VPX SUPPORT?
  The VPX I²C communication supports both PMBus and IPMI interfaces and complies with the VITA 46.11 specification. We recommend using the PMBus interface to query the status of the VPX. When using the PMBus interface, you will have a write PAGE command that will then allow you to select a specific output to query. When a read command is transmitted to the VPX module such as READ_VOUT and READ_IOUT, the VPX module will return the measurement information based on the selected page. The list of supported PMBus commands as well as IPMI commands can be found in the following user guides: VPX 3U I²C Operator’s Guide and/or VPX 6U I²C Operator’s Guide.
  
  If you still require support, please contact our Technical Support team to obtain help with your particular system.