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LP2983 as drop-in replacement for LP8358

Igor Zotman
Prodigy 60 points

What is the risk if we leave pin 4 at 2983 floating? This would happen if we disconnect a pull-up resistor for Power Good at LP8358. Of course a low ESR capacitor from output pin 5 to GND stays. The rest of the pins is compatible. We try to avoid re-spinning the PCB.

  • 0
    TI__Mastermind 22610 points

    "... Of course a low ESR capacitor from output pin 5 to GND stays ..."

    How low is 'low ESR'? I can not be too low.

    The ESR of the your capacitor from pin 5 (Vout) to GND must be similar to the internal resisance from pin 4 (ESR) to GND.

    There may be another option, check out the LP3984IMF-x.x, LP3990MF-x.x, or LP5951MF-x.x  if your input voltage is no more than 6V

  • 0 in reply to Donald Jones
    Prodigy 60 points

    I've selected LP3990-1.2.. Its data sheet calls for ESR of output capacitor  5 mOhm min, 500 mOhm max. At what frequency? For instance Kemet C0805C225K8RAC according to KEMET SPICE has 556 mOhm at 1kHz, 62.62 mOhm at 10 kHz, 13.5 mOhm at 100 kHz and absolute minimum 8.01 MOhm at 2.188 MHz.

    I feel it may be safe to use this cap.It is in present design. Please confirm.

    Thank you

  • 0 in reply to Igor Zotman
    TI__Mastermind 22610 points

    Yes, this seems to be an appropriate choice.

    Critical frequency is just below the 0db loop gain frequency, otherwise I go with100kHz.