PMP6776 power module for Xilinx Kintex7 FPGA failing

prashant kumar14

Other Parts Discussed in Thread: TPS54620, PMP6776, PMP

This ready made power module for Xilinx Kintex7 series FPGA is used as reference for designing the power supply portion of Xilinx Kintex 7 series FPGA based design. During Environmental stress screening tests it is found that only for lower temperature of -22 degrees the FPGA is not able to boot whereas for higher temperatures upto 55 degrees there is no problems at all for booting. This module is not able to provide the required in-rush current required at lower temperatures. Can any one suggest any solutions?

over 8 years ago

0 JohnTucker over 8 years ago

TI__Guru**** 191445 points

That PMP6676 has several different dc/dc converters providing different output voltages. Can you tell me which voltage rail is causing problems?

0 prashant kumar14 over 8 years ago in reply to JohnTucker

Prodigy 50 points

John its the TPS54620 which is supplying the VCCINT voltage for FPGA....probably it is not able to provide the in rush current required to boot kintex FPGA at lower temperatures. SS/TR pin connected to GND through 22nF capacitor as mentioned in the reference design, is this soft start capacitor limiting the in rush current? can i leave this pin floating? to decrease the ramp up time? please suggest

0 JohnTucker over 8 years ago in reply to prashant kumar14

TI__Guru**** 191445 points

Decreasing the SS time increases the inrush current (I = C*dV/dt). I suggest you try increasing the SS capacitance.

0 prashant kumar14 over 8 years ago in reply to prashant kumar14

Prodigy 50 points

alo john this VCCINT rail is the first in the sequence to power up with the power good enabling other regulators required by FPGA hence we are suspecting that this TPS54620 is failing. Is this reference design tested at lower temperatures of -22 degrees? if not then what changes you suggest to this deign to work at -22 degrees? Also four 100uF capacitors are connected in parallel at the output.. as shown in the reference design only one 100uF cap at output not sufficient? please suggest...

0 JohnTucker over 8 years ago in reply to prashant kumar14

TI__Guru**** 191445 points

So you do not know for sure which supply is causing the issue? You are only guessing at this point? It would be best if you monitor the output voltages to which if any are not powering up properly.

0 prashant kumar14 over 8 years ago in reply to JohnTucker

Prodigy 50 points

Yes john its TPS54620 generating vccaux 1.8 v which is creating problem when monitoring at -22 degrees it keeps fluctuating between 1.3 to 1.45 v JTAG scan chain not detected. When voltage raises to around 37 degree it reaches 1.7 v and at 55 degrees its 1.86 v and JTAG scan chain of FPGA detected.

0 prashant kumar14 over 8 years ago in reply to prashant kumar14

Prodigy 50 points

Even power good of this ic tps54620 enables other regulators in the sequencing is fine all other voltages are OK at -22 schematic and Bom for the design are same as PMP6776 so what is the problem suggest.

0 JohnTucker over 8 years ago in reply to prashant kumar14

TI__Guru**** 191445 points

So you are not actually using PMP6776, but copied that design to a PCB of your own design? Did you follow the PMP pcb layout? Can you post your layout? Can you provide waveforms of the 1.8 V output? Be sure to include the switch node and PWRGD.

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PMP6776 power module for Xilinx Kintex7 FPGA failing