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AD9371 auxADC reference

Question asked by RMahar on Aug 17, 2017
Latest reply on Aug 18, 2017 by sripad

Does the AD9371 auxADC have an internal reference?  The users guide or datasheet makes no mention I could find of needing an external reference, and the users guide shows a plot (figure 108) of ADC codes vs input voltage.


However, in the API comments, there is the following:

* \brief Sets up the auxiliary ADC


*  This function configures the AuxADC with the requested decimation.  The AuxADC clock is set as close

*  as possible to 40MHz.  The AuxADC conversion time = (1/40Mhz) * decimation, where the decimation ranges

*  from 256 AuxADC clock cycles to 32768 AuxADc clock cycles.


*  Note: The AuxADC is intended for relative measurements.  Two back to back measurements can allow a delta

*  measurement with 12bit resolution.  If absolute measurements are required, an accurate

*  reference should be first measured on AuxADC0 input and used to calibrate the offset/gain error of the AuxADC.

*  The reference would need to be measured before each measurement to account for measurement variations caused

*  by the transmitter/receiver transients as other circuits in the device are being powered up/down.


Is this correct?  We would need to use channel 0 for a reference, and make a measurement there before taking any other measurement to get an absolute voltage?