ADS1259EVM temperature drift

Hello Valentin,

The ADS1259 device offers low offset drift, (0.05uV/C Typical, 0.25uV/C maximum) and low Gain Drift (0.5ppm/C Typical, 2.5ppm/C Maximum).  The internal reference of the ADS1259 is guaranteed to 5ppm/C drift. The on-board reference (REF5025) also offers low drift (8ppm/C max in standard grade or it is also available on the high grade 3ppm/C max).   The PGA280 is a chopper stabilized instrumentation amplifier and also offers very low drift (+/-0.6uV/C max at Gain=1).  These components will not cause the 2% drift errors seen in the set up.

The ADS1259EVM board is not optimized to be a bench board to perform temperature characterization. For example, it has passive components that will drift such as the filter resistors, for example resistor RR1 on the Reference filter is a Thick film 10kOhm low precision 5% resistor, and the drift errors measured will be dominated by the drift of these passive components.

For example, if you are selecting the on-board REF5025 which is connected through the RR1 low precision resistor; and feeding the reference voltage though TP2 to the PGA280 inputs, the errors caused due to the drift of the RR1 resistor and leakage current of the D3 protective diode, are seen both at the signal path through the PGA280 inputs and the ADS1259 reference path.  In this set up, the errors due to drift of the RR1 resistor are reflected at the reference path and the PGA280 input path and will tend to cancel. When feeding the external +/-1V source; the error due to RR1 resistor drift will not cancel,  In addition, if there is any drift on the +/-1V external source, this will add to the error in the measurement.

-- In the set up, are you selecting the internal reference of the ADS1259 or the on-board REF5025?

-- What type of source are you using to generate the +/-1V voltage?  This will be required to be a very low drift/stable voltage source

Thank you and Best Regards,

Luis