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LM27762: Output decoupling caps for precision analog loads

Bryan McLaughlin
Expert 1110 points
Part Number: LM27762

Tool/software:

Hello,

I'm using the LM27762 to provide +/- 2.75V for precision analog circuitry. I'm trying to decide if the downstream analog ICs' decoupling caps should be differential (between +/-2.75V) or common-mode (each rail to GND).

"Build and test" is ideal but it's a TON of extra capacitors to be guessing at. 

Based on the charge pump architecture does the output ripple of LM27762 tend to be differential or common-mode? (If VOUT+ goes more positive does VOUT- also go positive, or goes it go in the opposite direction?)

Do you have recommendations from other precision analog applications?

Thanks!

  • 0
    TI__Mastermind 21580 points

    Hi Bryan,

    The output rails of the LM27762 are reference to the IC GND pin. The +ve and -ve rails are independent of each other (including ripple on the rails). 

    You should have downstream decoupling caps for each rail also referenced to GND. Any ripple/noise on each rail needs to flow back to the IC GND pin. 

    Best regards,

    Varun