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REF3440: ADS8885 ref voltage

Alen Barisic
Intellectual 1300 points
Part Number: REF3440
Other Parts Discussed in Thread: ADS8885, , OPA333, REF5045

Hi,

could you please review our ref voltage circuit for ADS8885? 

Thanks!

Best regards,

Alen

  • 0
    TI__Mastermind 19370 points

    Hi Alen,

    I can help you with the REF3440 section.

    The REF3440 requires an output capacitor on OUT_F to Gnd that is 1uF to 10uF.

    Is there a reason you need the 20kOhm resistor going to OUT_F? that will give an offset error.

  • 0 in reply to Marcoo Z
    TI__Intellectual 1300 points

    Hi Marco,

    the design is based on the following

    AS the RED3440 has a feedback, the idea was to save the OPA333.

    The temperature drift of all devices (resistors, OpAmp, REF + ADC) should be under 10ppm/°C.

    Could you please share your thoughts on this approach?

    Thanks!

    Best regards

    Alen

  • 0 in reply to Alen Barisic
    TI__Mastermind 19370 points

    HI Alen,

    I see it forms an RC filter. That is fair.

    I have not tried this approach on the bench and my bench capabilities are limited. I would still add the 1uF directly on the Out_F output due to stability.

    The REF5045 also requires this capacitor. It is not shown in that figure but it does appear in the schematic.