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WEBENCH® Tools/TPS40210: MOSFET Damage at no load startup

Nithin Mohanan
Prodigy 220 points
Part Number: TPS40210
Other Parts Discussed in Thread: CSD19537Q3

Tool/software: WEBENCH® Design Tools

Hi,

We are using the TPS40210 for generating the 48V phantom voltage for one of our application. We have simulated same in WEBENCH and followed the refference design with some slight modifications in the component selection. The WEBENCH simulation report is also attached here.

webench_design_3656248_20_312178119.pdf

The current schematic of our design is same as that of below image 

Initially when we test the board with no load condition by gradually increasing the input voltage from 6V to 12V the regulator was working fine and we could see the 48V at the output also.. But when we give a steady 12V input the output voltage drops suddenly to around 10V and after a few seconds we could see smoke from the board, when we inspected the board it seems the MOSFET is damaged.all this testings were done with no load condition only.

The main two difference between the simulation and our actual design was the MOSFET and Diode selection. Since our board the max load current can be around mA from the48V we thought a MOSFET with Id of 1A will be sufficient enough as the switching current is seems to be around 500mA only for the 60mA load current.

But all our testing was in no load conditions only and even in no load condition also the MOSFET is damaged..

Now we changed the MOSFET to the same part as that of the TI WEBENCH simulation report and CSD19537Q3 is soldered to the board with little rework to replace the initial BSH114 MOSFET. Still then we saw smoke when we start the regulator by gradually increasing the input volatge. This time when the input voltage was 5V, the current in the power supply increases to 1A and we could see smoke coming from the MOSFET area of the board..

Can any other have the such an issue of damaging the MOSFET even in no load condition..?

We have followed the all the design recommendations and tried to follow the WEBENCH design as close as possible.. what may be the possible reasons for the MOSFET damage..?

We checked the gate drive waveform and is seems to be more or less close to the simulation report ie. 580KHz at 86% dutycycle..scope waveform is also given below

  • 0
    TI__Guru* 76205 points
    Hi Nithin,

    Thank you for using the TPS4010 in you design. I am afraid your circuit loop is not stable. Could you monitor Q301 drain voltage? Then, would you please short L302 and re-run the test and see if the damage still occurs?

    Best Regards,
    Youhao Xi, System and Applications Engineering, APP-BMC-BCS, TI
  • 0 in reply to Youhao Xi
    Prodigy 220 points

    Hi Youhao,

    Thanks for your response and in between testing we observed some different observations as follows,

    We have changed the MOSFET to ti recommended one and gradually increased the input value , then the output was perfect at 48V, but sudden starting of regulator with 12V input its output is only 12V and we checked the input ramp up and suspected the initial inrush current , so to increase the soft start we changed the SS capacitor to 1uF to get a max soft start then we could able to see the output voltage of 48V even when a steady 12V input is given..We tried multiple turn on and off to check output is stable and is ok also...

    But one thing we are now facing is that even with no load condition it consumes 200mA current from input..

    What may be the reason for this..??

    We haven't connected anything in the output 48V rail and still its drawing 200mA..

  • 0 in reply to Nithin Mohanan
    TI__Guru* 76205 points
    It sounds weird. From your schematic there is now such leak path that can draw 200mA from the input. How much current consumption from input if you disable the circuit by pulling pin 3 high? With the circuit disabled, can you apply 48V to the output rail and see how much current it taken?