We are considering new adoption of ADS8904B.
From the specifications of the product under development, the ADC is single-ended input.
SAR with high resolution (19bit or more) is required.
I would like to use the ADS8904B with the following inputs, is there any problem?
・REFIN:4.7Vref input
・REFM:to GND
・AINP:0~5V input
・AINM:to GND
Sorry for the vague question.
Hello,
Welcome to the TI E2E community.
Your question is clear: unfortunately, the ADS8904B requires a fully differential input where the input common mode voltage (average of the 2 inputs) must be equal to Vref/2. AINM cannot be connected to a fixed DC voltage, such as GND. In your case, the input common mode voltage should be 4.7V/2=2.35V.
Take a look at this TI Precision Labs that describes the requirements of a fully differential input in more detail.
https://training.ti.com/sites/default/files/docs/adcs-sar-adc-input-types-presentation-quiz.pdf
You can provide a fully differential input by using either a two op-amp circuit or a fully differential amplifier. The below application notes discuss both options.
Single-ended to differential using a two op-amp circuit
Single-ended to differential signal conversion using an op amp and FDA for unipolar signals
Regards,
Keith Nicholas
Precision ADC Applications
