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ADS9224R: External reference

Romain Gouget
Prodigy 20 points
Part Number: ADS9224R

Hello,

I would like to know if we could use an external reference with the ADS9224R. Indeed there is REFP/REFN and REFOUT available on the component so can we use one of these pins with an external reference and bypass the internal reference ?

Best regards,

Romain

  • +1
    TI__Guru 64056 points

    Hello Romain,

    Welcome to our forum and thank you for your post.

    Yes, there are separate power-down options for the internal reference voltage, the Channel A and B ADCs + reference buffers, and for the REFby2 output. These power-down bit settings are all contained in the POWER_DOWN_CFG register (address = 01h). The internal reference buffers have a fixed gain of 1.6384 V/V. I suggest substituting an external reference voltage equal to the nominal 2.5 V and connecting it to the REFOUT pin after disabling the internal reference voltage, then using the two internal reference buffers to drive each ADC's reference input. Unfortunately, the individual reference buffers cannot be independently disabled without also disabling the ADC channels themselves.

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 20 points

    Hello Ryan,

    Thank you for your answer, so we cannot supply the part with an external reference higher than 2.5V? For example can we put the external reference voltage directly into REFP/REFN instead of REFOUT?

  • +1 in reply to Romain Gouget
    TI__Guru 64056 points

    Hi Romain,

    The internal reference buffers will always be driving a voltage on the REFP pins. The only was to power down the reference buffers is to also power down the ADC channels. An external reference voltage can therefore only be applied to REFOUT.

    Regards,

    Ryan