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Can LM2937ES-3.3/NOPB LDO sink any transient current capability?

Kedar Bhave
Prodigy 20 points
Other Parts Discussed in Thread: LM2937

Hello,

We are using LM2937ES-3.3/NOPB LDO & this 3.3V supply given to Microcotroller , External ADC & other circuits. Each ADC channel have some input & for protection we provide Protection circuit (back-back Schottkey diode BAT54S) on each channel input. We have some query regarding LDO & the protection circuit which we mentioned, is it correct ?

1)If suppose transients(more that 3.3V) comes on ADC input channels, can LM2937ES-3.3/NOPB LDO IC sustained for that transients?

2)Will LM2937ES-3.3 sink the transient current? Or

3) Is this protection circuit Okay( Back - back BAT54S-HE3-08 diodes connection on each ADC Input channels)?

 

 

  • 0
    TI__Mastermind 22610 points

    Q1) If suppose transients(more that 3.3V) comes on ADC input channels, can LM2937ES-3.3/NOPB LDO IC sustained for that transients?

    A1) All depends on how much more than 3.3V we're talkig about. Up to the input voltage of 5V there should not be any problem. Vout > Vin is not recommended.

    Q2) Will LM2937ES-3.3 sink the transient current?

    A2:) LM2937 output does not have any current sink capability.

    Q3) Is this protection circuit Okay (Back-back BAT54S-HE3-08 diodes connection on each ADC Input channels)?

    A3) Depends on what you are trying to proctect against. For brief voltage spikes less than +/-5V ... maybe. For long term DC voltages, or high voltage transients, probably not. I would suggest: 1) some modest series R on each input to limit the current during +/- transient voltage events; 2) add small C off the a/d input pins to gnd to add RC low pass to filter out any fast transients; 3) clamp the protection circuit +V with a zener rather than LM2937 output.

    Perhaps some A/D experts will suggest other input protection schemes.