Delta sigma max input voltage on AIN+ and AIN-

[www111]

Hello,

I'm using the ADS1259 from TI and i want to know what is the max input voltage swing on AIN+ and Ain- if I use Vref 5V and Avss=5V and if I use bipolar supply +-2.5V can i use the 5V reference or must use 2.5V reference?

Can I have AIN+ and AIN- from -2.5V to 2.5V with supply 5V and reference 5V ?
Thnaks.

 

[FvM]

The datasheet clarifies, that VREFP-VREFN can be as high as AVDD-AVSS + 200 mV. In this case, you'll need an external +/- 2.5 V reference source when using a bipolar analog suppy.

 

[www111]

Ok,

In my case I have two input voltage and they are always equal by amplitude and opposite sign so the difference is always positiv.

eg: Vp=1.25V Vn=-1.25V the value depends on gain of an Preamp. Vd=Vp-Vn=2.5V

What configuration of ads1259 should I use , it is possible for such an signal to use ADC's supply form 0-5V?

 

[FvM]

If you can't shift the input voltage to positive range, e.g. centered around 2.5 V rather than zero, you need a bipolar supply, usually +/- 2.5V.

 

[www111]

How could I shift it?

What is better?
and if I apply REF5025 to VREFP pin , what should I apply to VREFN pin? and AVDD=2.5V, AVSS=-2.5V that mean them max input voltage on one input pis is 2.5V or -2.5V ?