i have a problem in reading values from ads1672(datasheet). i setup this circuit: ads1672 with a potentiometer in the positive input and grounded negative input

the Reference voltage is +3.V (REF5030-TI page)

when potentiometer is @ +1.6V (i measured this by multi-meter) this out +2.9V!! and when potentiometer is @ +1.4 the ads1672 output is -2.9V!! and when potentiometer is beyond +3v ads1672 output is almost +0V also when potentiometer is zero ads1672 ouput is -0V!!

Why!! any body have any idea?

Firsts Question: are this setup (with a potentiometer in the positive input and grounded negative input) is good for test and setting up a differential ADC??

Second Question: what is VCM role in my circuit? (with respect to Refrence Voltage=3.v)

i think (ReferenceVoltage/2 =1.5) is center of input ads1672. is it right. but why??

Thanks All


1 Answer 1


The data sheet on page 3 tells you this: -

Common-mode input voltage VCM = (AINP + AINN)/2 = 2.5 V typically

So if AINN is 0 volts then the only typically valid value for AINP is 5 volts.

You have a pot on AINP and with 0 volts on AINN this set-up won't work.

See also the notes on page 14 about how to drive the inputs - inputs need to be driven differentially and centred about 2.5 volts. See page 26 for circuit examples of interfacing to the analogue inputs of this chip.

  • \$\begingroup\$ thank for your reply... but we are not in common mode, we are in differential mode \$\endgroup\$ Commented Jun 7, 2018 at 20:11
  • \$\begingroup\$ @ali you need to read up on this and recognise that you are breaking the common mode rules for this ADC despite your attempts to apply a differential signal. \$\endgroup\$
    – Andy aka
    Commented Jun 7, 2018 at 20:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.