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OPA333AIDBVR

ASWATHY VV
Prodigy 130 points
Other Parts Discussed in Thread: ADS8881

THE DESIGN USING THESE OP AMPS IS TO GENERATE A REFERNCE VOLTAGE FOR THE ADC "ADS8881IDGS". THE INPUT VOLTAGE IS SET TO 5.5V TO THE OP AMP ANAD HAS TO GENERAT A ADC_REF VOLTAGE OF 4.5V ACCORDING TO THE DATASHEETS.

  • 0
    Guru 140200 points

    Hi Aswathy,

    why aren't you following the recommendation given in figure 65 of datasheet of ADS8881? Your R152 is way too big and your C169 is way too little.

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 55466 points

    Hi Aswathy,

    As Kai has mentioned, the value of the R152 resistor needs to be a much smaller 0.2Ω, and the proper REF bypass capacitor needs to be 10-μF as recommended on the ADS8881 datasheet. 

    The 10-μF REF bypass capacitor along with the 0.2Ω resistor need to be placed in very close proximity to the ADS8881 REF pin.  Choose a 10-μF, X7R-grade, 0805-size, ceramic capacitor with at least a 10-V rating for good performance. Below is the circuit recommended in the ADS8881 datasheet.  Also, please refer to Figure 77 of the ADS8881 datasheet for a board layout example showing the optimal placement of the 10-μF bypass capacitor and 0.2Ω  resistor in close proximity to the REF input of the ADS8881.

    Thank you and Regards,

    Luis