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RE: TPS5420: replacing with TPS54240 or TPS54202

FJ
Intellectual 360 points
Other Parts Discussed in Thread: TPS5420, LMZ21700, TPS54202, LMZM23601, LMZ21701, LMZM23600Thanks for the info.

Two other ?'s

I have used the TPS5420 in a application for years with no issues. In a revision, I tried using a LMZ21700 module. The board is used to control some P channel fets to drive automotive style fans that draw ~20Amps. The LMZ just provides 5 volts LCD display and mainly to feed 3.3 volt regulator for CPU power, but nothing to do with fet drive or control. In testing, all was fine until I tried to PWM the fan. First Pulse the LMZ21700 went up in flames. Built and tried another PCB, same result, but I caught it fast to see input pin on LMZ burning. I speculate 12volt battery supply got transient from back EMF of fan that may have gone above the 17volt max limit for LMZ21700. The lmz went up similar to applying 20 volts to a 5 volt tantalum cap! Wouldn't think a short pulse would do that.
1) Do you think my transient assumption is reasonable?

This is why I am trying to stick with something similar to the TPS5420 (TPS54202), but also considering the LMZM23601 module.

2) Would this module be similar in capabilities to the TPS5420 or might I see smoke again!
  • 0
    TI__Genius 15810 points
    Hello FJ!
    I can try to answer your question regarding the LMZ21701 power module. Voltage transients at the input can definitely cause damage and this situation can be exacerbated by an un-optimized layout. If you would like to we could help you review it.
    The LMZM23600 would be able to handle a voltage swing up to 36V comfortably. It is a 1A device unlike the TPS5420. As long as you have a good layout and follow the datasheet recommendations you shouldn't have any issues operating your system with the LMZM23601.