Understanding vbias & IDAC in ADS1248

Thread Starter


Joined Feb 2, 2012
1. I am using ADS1248 & its pdf I have attached. I am interfacing ungrounded thermocouple whose voltage varies from -6 to +50mV.
Also I have attached the ckt which I am using. Recommended condition is to use Vbias = 2.5V at -ve input. I don't understand what exactly it do. I have attached a ckt which I think should be equivalent ckt when I use vbias.

Rotate the ckt attached.

2. IDAC is constant current source. But if in datasheet attached , on page 57 there is ckt given on which two IDAC are connected on both A+ & A- pins. Does that that current flows out of A+ & A- pin respectively.



Joined Apr 24, 2011
I've never used one of these, but when I'm using a new IC I look for any help the manufacturer gives, such as sample designs or development boards that may not be covered in the data sheet.

I do check the data sheet for any suggested designs. (Seems this one just has an RTD device).

See if "BIAS VOLTAGE GENERATION" on sheet 29 of that data sheet makes any sense to you.