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Regarding ADS1248

Other Parts Discussed in Thread: ADS1248

i am using ADS1248 for my Sensor application. In the data sheet they have have mentioned formulas for Common mode input range of ADC.

My Question is

1.The ADC Common-mode input range formula given in ADC datasheet is applicable for the input of ADC (i.e  before PGA) (OR) After PGA ( i.e  at the input of Delta-Sigma modulator inside the ADC)?


 
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 



 
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 


  • Sivarama,


    The ADC common-mode input range is given for the input of the PGA, not for the input of the ADC. For the ADS1248, you cannot directly reach the input of the ADC itself.

    If you look at the PGA, the topology is the front end of an instrumentation amplifier. The equation given is a consequence of the limitations of the input of the PGA and of the output of the PGA when it is in gain.


    Joseph Wu