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 one perfect EMI strategy for all applications, but some basic thought before-hand can make the task much easier. The first step is to make sure that the location of components minimizes noise. For example, de-coupling capacitors should be located as close as possible to the converter, especially X-caps and Y-caps. Use ground planes to minimize radiated coupling, minimize the cross sectional area of sensitive nodes, minimize the cross sectional area of high current nodes that may radiate such as those from common mode capacitors. The location of the EMI components is critical; avoid placing the converter in close proximity to your filter to avoid noise coupling back into the filter. Keep in mind that you are not just filtering the power supply, but all the circuitry that the converter is powering as well. Most of today's communication cabinets employ as much local filtering as possible at the card level, and then another filter at the power entry module, where the power feeds will enter your cabinet. SynQor has an EMI application note that further details these principles and includes recommendations for 1 and 2 stage filters that are designed around SynQor's converters. Please contact SynQor directly for design assistance, or email support@synqor.com .

• What type of conducted line filter should I use?

  While a pre-designed EMI filter may be adequate for a particular converter, there is no guarantee that it will suppress other sources of conducted EMI that are present on your board, such as the noise from high-speed processors and other digital logic devices. Better value and performance will be obtained with a discrete filter design. The key to a smooth EMI compliance process is to design as much filtering as possible onto your circuit pack. This will allow the flexibility to tweak and modify components when the initial testing is performed. It is best to over-design up front than be caught off guard; components can easily be deleted once the initial testing is completed. Adding components to an existing PCB design is much more difficult and can yield unpredictable results. SynQor has suggested one and two stage filters that are simple and reliable to implement, and for much less cost than an off-the-shelf filter. These suggested filter circuits are in SynQor's EMI application note. In general most modern communications equipment uses a local EMI filter on each of the circuit cards, and a final shielded filter located in or near the power entry module.

• How do I choose Y-Caps?

  Y-caps are the EMI capacitors that are connected from the input power feeds to chassis ground. Sometimes they are connected from each converter's power output terminal to chassis ground as well. SynQor filter designs use 2700pF Y-Caps. The voltage rating depends on the insulation and isolation safety rating of the -48VDC supply. If you are unsure of these attributes, use capacitors rated to 2000V. If the -48V is a reinforced insulation scheme, then 100V rated capacitors will suffice.

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

  All SynQor bricks use a C-L-C input filter. All SynQor bricks have an L-C filter. The value of these components can be found in SynQor's EMI application note, or in the appropriate product datasheets.

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

  While it is preferable to have and to use a chassis ground, it is not mandatory. Under some circumstances a chassis ground will not be available for the input conducted EMI filter. If this is the case, you will want to use a different filter topology. Contact SynQor Support for this circuit.

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

  For multiple converters, you can still use SynQor's recommended filter design, just be sure to size the individual components to handle the maximum current at the lowest input voltage.

• 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?

  In general, a filter that has been previously designed around a 200 to 500KHz fixed frequency converter will be adequate for an equivalent SynQor converter. SynQor's converters have lower common mode noise due to their lack of a baseplate. Baseplated units have higher common mode noise as the switching noise of the power semiconductor's couples through the parasitic capacitance of the baseplate.

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Radiated EMI

• Are there any special concerns with an open frame converter?

  SynQor open frame converters are no worse, and often better, than baseplated converters. In general, most baseplated units have a plastic cover, and in 3 Meter and 10 Meter far field measurements offer no advantage compared to the SynQor open frame design. SynQor's unique topology and reduced common mode noise have a significant advantage over other manufacturers' converters in regards to reducing radiated emissions.

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Near-field EMI

• How will an open frame converter perform versus a baseplated 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 baseplated 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 baseplated 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.

• 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.

• What about magnetic fields?

  Baseplated converters will offer improved protection from near B-field radiation. At most frequencies, a baseplated 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.
  
   

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Enable Circuits/Inrush Control

• Why do I need an inrush controller?

  All converters act as negative resistors, and all power distribution paths have some inductance. These two elements require that some electrolytic capacitance be placed across a converter's input terminals to compensate for the negative resistance, preventing a possible oscillation. If a circuit card containing a converter is hot swapped into a back plane, the charging of the electrolytic capacitor can cause a low voltage transient or glitch on the 48V supply, which could upset other circuits sharing the common 48V feed. To prevent this glitch on the input rail, an inrush control circuit should be placed in series with the 48V feed. An inrush control circuit limits the charging of the 48V rail. A good example of a controller for an inrush circuit is Linear Technology's LT1640 and LT1641, Summit Micro's SMH4804, or Supertex's HV300 series.

• 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).

• Why is there a 200ms delay at turn on for your new family of converters?

  Most all of SynQor's converters have a 200ms startup delay at initial turn on, and after a fault condition such as OVP or Over Temperature Shutdown. After recovering from any fault condition, the converter will not turn on for 200ms. When the bus voltage is below the under voltage lockout, this is considered a fault condition. This behavior is detailed in our data sheets, and should be studied before implementing an inrush or sequencing strategy. The delay ensures that the start up behavior is always consistent and well controlled. If the input voltage were to glitch momentarily to zero volts, then return to the full bus voltage, the delay gives the control circuitry time to return to proper startup conditions. Since the control circuitry has no voltage when the input voltage is brought to zero, it is difficult to distinguish between power up after a glitch and initial power up. Therefore, the module treats all recoveries from undervoltage lockout identically. The delay on power up also guarantees that the input voltage is well within the operating range before powering up the output load. Note that after the delay time has passed, the module will turn on quickly when the ON/OFF pin is set to the enabled state.

• 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.

• Any suggestions on using Summit Micro's hot swap controllers?

  It is important when defining a system's sequencing requirement that SynQor's 200ms initialization period be considered. As an example, if you are using a programmable delay to enable multiple converters in a specific sequence, you must make sure the delay is approximately 200ms. When using the Summit Micro devices, make sure to use their 160ms delay setting, and use the second delay tap to enable the first converter. As an example for a three converter solution, you use the SMH4804 where PG#2 would enable the first converter, PG#3 for the second and so on.

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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?

  All of SynQor's converters are fully isolated which allows them to generate negative output voltages. Simply connect the Vout+ terminal to the system output ground, and a negative voltage will be generated on the Vout- terminal.

• I have a negative 48V bus. Can I use SynQor converters?

  Because the converter is isolated, the Vin+ terminal can be tied to the input ground of a -48V system. The Vin- terminal should then be connected to the -48V rail. Keep in mind that the primary side signal pins are referenced to the Vin- terminal in all cases.

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

  Each product has a label which reveals the product part number, revision letter code and serial number for that module. This information can be found on the label in the specific locations detailed in this photo.

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Safety Issues

• Where do I find the safety certifications?

  All of SynQor's safety certificates can be found in our Quality & Compliance page.

• Where are the conditions of acceptability?

  All safety certifications, including the conditions of acceptability can be downloaded in PDF form from our Quality & Compliance page

• How do I choose a fuse?

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

• What is creepage and clearance?

  Safety certification requires that the primary 48V circuitry (Primary) and the low voltage output (Secondary) circuitry be separated from each other. SynQor's converters use a Basic level of insulation, with 2000V of isolation. As such, all SynQor converters have a minimum distance of 1.4mm between primary and secondary circuitry.

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

  Insulation refers to the design parameters used to isolate the 48V primary side signals from the low voltage 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. All SynQor converters use Basic Insulation which meets the most stringent requirements for 48V based DC systems. 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 all converters capable of withstanding a 2000V breakdown.

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

  In the United States, UL defines an "Unsafe" voltage as 60V, this is called the SELV (Safety Extra Low Voltage) limit. At input voltages of 0 to 60V, the highest voltage will be across the midbuss capacitors, this is an AC signal, operating at the switching frequency, with a maximum peak to peak amplitude of about 58V. Above a DC input of 60V the maximum voltage is the input voltage across the primary switching FETS, which is approximately Vin plus a few volts.

• Are safety covers recommended for the converters or is a "danger high voltage" or similar label required on the surface of the converters?

  If the input voltage remains below 60VDC, then all voltages are SELV, and no special care is needed. If the input voltage rises above 60VDC, then there will be non SELV voltages on the top side of the converter. The exact need for warning labels or covers, depends on the safety agency approvals needed. For UL, if non-technicians are to be allowed to change system configurations, i.e add more memory cards, the machine should be powered off to prevent access to the non-SELV voltages.

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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 and 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?

  SynThe 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.

• What is SynQor's qualification process?

  SynQor has a three-step release process: POD, POM, and Qualification. POD, or Proof Of Design, is the process during which the converter's performance is evaluated and characterized over all rated operating conditions and beyond, in accordance with HALT principles. POD measures component stresses to ensure that design guidelines are met and that no components are over-stressed in both normal and abnormal 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, DFM, and waveform analysis.
  
  POM, or Proof Of Manufacturing, ensures that SynQor has designed a part that can be manufactured, is reliable, and has proper margins to be run in a high volume factory. POM ensures that target yields are met, that our ATE systems are optimized, and any new manufacturing equipment or processes constructed are optimized. Statistical Process Control analysis at this stage is mandatory, and CpKs are scrutinized to ensure that SynQor has a repeatable and consistent process.
  
  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 our customers' expectations. Testing at this stage includes aggressive thermal shock cycles, extended high temperature life and humidity tests, vibration and mechanical shock tests in accordance with military standards, terminal solderability, full mechanical and dimensional compliance, as well as a thorough examination of the solder and manufacturing quality.

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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 at the load current and input voltage.
  • The worst case ambient temperature.
  • The amount of airflow available.
  • The maximum baseplate temperature of the converter, which is 100C for all SynQor baseplated converters.

  Example:
  What size heatsink is required for 3.3V quarterbrick at 20A, 48V input, 70C ambient, and 200LFM of airflow?

  Using SynQor's PQ48033QGA25 data sheet figure 3, at 48V input, and with a 20A load, the power dissipated by the SynQor's 3.3V quarterbrick converter is about 8.5 Watts. The allowable temperature rise is simply the maximum baseplate temperature minus the worst case ambient temperature. So in this example, 100C - 70C = 30C allowable rise. The thermal impedance of the heatsink required is simply the allowable temperature rise, divided by the power dissipated. In our example this is 30C/8.5Watts, giving a maximum thermal impedance requirement for our heatsink of 3.53C/W at 200LFM. Using any standard heatsink catalog you can now select a heatsink. A good choice would be Intricast's (www.intricast.com) HS1361XM01 heatsink, which is 0.5" tall and has a thermal impedance of 2.60 C/W at 200LFM.

• How do I measure the temperature on your converters? Where do I place thermocouples?

  SynQor's derating curves are created based on a derating of 125C for switching MOSFETs. Using SynQor's data sheet, locate the thermal image, which shows the hottest components on the power supply. Generally you will want to measure the input MOSFETs, the isolation stage MOSFETs, and the output synchronous rectifiers. Care should be taken not to block too much of a device's surface area, as this could significantly reduce its ability to remove heat via convection.

• How does SynQor's thermal protection work, and where is the sensor?

  OHeat 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?

  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.