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ADS8668: Vref is not coming

Yogesh Gajul
Prodigy 10 points

Part Number: ADS8668
Other Parts Discussed in Thread: ADS8688

Hello,

I have connected ADS8668 as shown in the schematic below. I am trying to use the ADC with internal reference voltage but I am not able to get the reference voltage at the pin REFIO. 

Can anyone suggest changes (if any) so that I can make use of the internal reference voltage on the IC.

  • 0
    TI__Guru 50585 points

    Hi Yogesh,

    Pin 30 is the AVDD and it should be connected your 5VD power supply in your circuit, However, you connected it to the AGND. This is the reason your ADC did not work as expected.

    One suggestion is, R148 can be DNP because ALARM is an output signal.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 10 points

    Hi Dale,

    I would like to thank you for replying. We figured out the same issue after posting. 

    Anyways your suggestions is really appreciable. Thanks for your spontaneous support.

    Best Regards,

    Yogesh

  • 0
    Prodigy 10 points

    Hey Dale,

    Thanks for the reply. I corrected the mistake and I am able to get the reference voltage. I am trying to use ADS8668 in manual mode i.e., I am trying to continuously read the values from Channel 1. I am facing some difficulty in how to read back the digital values. Can you please suggest an example code for reference so that I can verify whether I am sending all the commands to use the ADC in manual mode and also I will get an idea how I can read back the measured values digital values.

    With Regards,

    Yogesh

  • 0 in reply to Yogesh Gajul
    TI__Guru 50585 points

    Hi Yogesh,

    There is a sample code for ADS8688 on TI.com which can be used for ADS8668 as well, please check Source File (ti-ads8688.c) from the following link:

    http://www.ti.com/tool/ADS8688SW-LINUX

    Best regards

    Dale