reference voltage for ADC

[nxing]

Hello everybody,

I got confused by one simple question and hope some body can provide some ideas:

I want to design a ADC with differential input (each of them)between +,- 500mv. Also, I will put two reference voltage, say "refp" and "refn". My question is which value I should setup refp and refn. If I set rep = 500mv and refn =-500mv, then, the differential value of input signal will between +,- 1v. If I set refp=1v and refn=-1v, each input signal will not exceed
+,- 500mv. What's the correct choice?

Thanks

 

[edonor]

Look the ADS1243 from Texas Instruments

 

[Hughes]

Set rep=500mV, ren=-500mV

 

[shiowjyh]

I will say yes if you are not using a preamp circuit to amplify your differential signal.
BTW, if you are still working on adc based on Thmoas Cho's Thesis, see more on his IEEE JSSC publication Fig.2.
This means while your differential input is +-500mv, and your reference(vref) setup would be as same as the differential input.

IEEE JSSC, vol 30, no 3, march 1995
A 10b, 20Msample/s, 35 mW pipeline A/D converter
Thomas Byunghak Cho and Paul R. Gray

Regards,