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ADS1258 +/- 2.0V input

tds
Prodigy 90 points

Other Parts Discussed in Thread: ADS1258

Hi

I use the ADS1258 with the following voltag:

AVDD +2.5V

AVSS -2.5V

VREFP 2.048V

VREFN -2.048V

DVDD 3.3V

So, my problem.

I have a problem getting full range out from the ADS1258.

From the datasheet: Full-scale input = +/- 1.06 * Vref.   Vref is defined as VREFP-VREFN. ==> 2.048 - -2.048 = 4.096.

 

Since the range is  +/- 1.06 * Vref, is then the total range +/-1.06 * 4.096 ?  

 (Maximum input is to be in a range of AVSS/AVDD +100mV, so I can see the problem if the answer is yes)

 

Best regards

Tor Dag

 

 

 

 

 

  • 0
    TI__Mastermind 43915 points

    Hi Tor Dag, 

    In theory, Yes, you have the equation for the range correct. The total range is +/-1.06*4.096 (4.34V) and you can reach this range if you are using the ADC input differentially. Therefore, in your configuration when run differentially, you can have the AINN input set at -2.0V and AINP set at 2.34V and should read out full scale positive. If AINN is set at 2.34V and AINP set at -2.0V, you will read out full scale negative. 

    If your setup is single ended, AINP with respect to ACOM, then you will not be able to reach full scale. In this case, you will want to use a ~2.5V reference and then you will be able to swing positive from 0 to 2.5V and negative from 0 to -2.5V in your configuration. 

    Is your design set for single ended or differential inputs? 

    Regards,

    Tony Calabria 

  • 0 in reply to Tony Calabria
    Prodigy 90 points

    I see.

    I have done some modification, and it is now OK.

    Thank you.