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Original question:

TPS40170: Device damage at input voltage above 42VDC

TPS40170: TPS40170 stopped to output with loads about 150 watt

user5992127
Prodigy 60 points
Part Number: TPS40170

An TPS40170 Buck Circuit which conversion 48V input supply to 24V output with the maximum current about 10A, there are something trouble with the circuit,

1. some boards (about one in ten) will be stopped to supply 24V to loads about 150 Watt, 

2. few boards (about one in twenty) can be heared that the power conductor is whistling when connected loads,

Would you like to give me some advices for the troubleshooting, as I tried some compensation loop adjust, but it didnot work.

There are some waveform test of TPS40170 pins:

The comp pin, I think the below is right (The waveform is the comp pin of an EVM board)

TPS40170 Buck.pdf

  • 0
    TI__Mastermind 34875 points

    Hi 

    Did you calculate the compensation network with below software?

    http://www.ti.com/lit/zip/SLUC263?jktype=tools_software

    I have a quick look at the schematic, C34 and C35 voltage rating should be 50V or higher, calculate compensation with effective capacitance with 50% derating.

    Can you measure loop response  on R29? if you don't have the proper instrument, then do load transient testing with shortest thick wiring on output, load step from 1A to 6A at 1A/us. pls refer to below note:

     AN-1733 Load Transient Testing Simplified

    BTW, it's NOT recommended to use inductor in parallel like L8 and L1, L9 and L2 in your circuit.

  • 0 in reply to Andy Chen
    Prodigy 60 points

    Hi Andy,

    Thanks for your suggestions.

    I have calculated the compensation network, but maybe the parameter is not correct, and I will check it again.

    ps,

    BTW, it's NOT recommended to use inductor in parallel like L8 and L1, L9 and L2 in your circuit.

    -- It's inductor compatible for DC-DC bucks, not mount simultanously.