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Original question:

PCM1865: 10uF input capacitor removal

PCM1865: PCM1865 and OPA1637 conection

Ignacio Olazabal
Prodigy 40 points
Part Number: PCM1865

Hi, I have connected PCM1865's Vref to my OPA1865's VCOM, im wondering if i should divide it by two or not. My OPA is conected to +18v / -18v. But Ive read VCOM should be connected to AVDD/2 so im not sure. Should i divide it by two like this configuration?

The thing that makes me doubt is that the opa in this configuration has Vs- to gnd and its not differential. 

This is my configuration:

  • 0
    TI__Mastermind 29190 points

    Hi Ignacio,

    VREF is already set internally to be AVDD/2 so no divider is necessary. However I'm not sure that R101 and R140 are necessary. Can you explain to me your thought process behind those two resistors?

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 40 points

    Sorry for asking in two different places my follow up question I wasnt sure how the forum worked and thankyou for the quick response. I am currently replacing the person who started this project and im trying to figure out his design, im still not sure why those resistors are placed there, R101 is 1k and R140 is 100, i believe that if VREF is AVDD/2 there shouldnt be any more voltage drop, just the opas follower circuits as it goes through a connector, maybe it has something to do with the fact that it goes through a connector but im not sure. I dont believe they are needed. Thank you for all your help!