This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1293: External Vref Specification

Part Number: ADS1293

Hi,

I suppose there is no specification about external Vref.

Would you tell me the specifications if you know?

Thank you in advance.

Best Regards,

  • Hello Takumi-san,

    An external reference can be applied to the CVREF pin when the internal reference is powered off. The range can be any voltage within the power supply rails. However, the input will not be high impedance. The ADC will sample the reference at the modulator frequency, so make sure a bypass capacitor remains at CVREF to serve as a reservoir of charge for the reference sampling circuit.

    Regards,
    Brian
  • Hi Brian-san,

    Thank you very much for your reply.

    I understood that externak Vref range is 0V to VDD, for example, in case VDD is 3.3V then Vref is 0 to 3.3V.

    Is my understanding correct?

    And will you tell me the Vref ON/OFF timing specification against VDD and VDDIO if you have?

    Is there no specification??

    Regards, 

  • Takumi-san,

    You are correct about the range.

    Timing may be difficult. As you can see on page 49 in the datasheet in the REF_CN register description, the internal reference is powered on by default. To protect against a short circuit, you should set the SHDN_REF bit before applying the external reference voltage. This requires that you wait for the ADS1293 to power up, then write to the register, then enable the external reference.

    Out of curiosity, is there a reason you cannot use the internal reference?

    Brian
  • Hi Brian-san,

    Thank you for your kind reply.
    In fact, this question is from my customer.
    I will ask the customer.

    Regards,