Best Method of Amplification to get Better Performance from PSoC® 3 OR PSoC 5 Del Sig ADC - KBA81866

Version: **

 

Question: What are the different possible methods of amplification available for using with PSoC 3 or PSoC 5 Del Sig ADC? What is the best method of them to get better performance?

 

Answer:

 

The input signal of Del-Sig ADC can be amplified by the following possible ways:

  1.   Using the ADC Buffer at the input of Delta Sigma Modulator (ADC Buffer gain can be configured in the Del Sig ADC component configuration window)
  2.   Using a PGA at the input of ADC (Drag and drop the PGA component and configure its gain in PGA component configuration window)
  3.   Using Modulator gain by selecting lower input range of ADC (only in Differential Mode)
                                                                                                                                                        
    
      Input Range
   
    
      Equivalent Modulator Gain
   
    
      -Input +/- Vref
   
    
      1
   
    
      -Input +/- Vref/2
   
    
      2
   
    
      -Input +/- Vref/4
   
    
      4
   
    
      -Input +/- Vref/8
   
    
      8
   
    
      -Input +/- Vref/16
   
    
      16
   
    
      -Input +/- 2 * Vref
   
    
      1/2
   
    
      -Input +/- 6 * Vref
   
    
      1/6
   

In order to get better results, the following order of amplification is preferred:

Modulator Gain > ADC Buffer > PGA

Note: What is modulator gain in Del Sig ADC?

Delta sigma modulator is a Switched capacitor block with input & feedback capacitors around OpAmps. The Capacitors sizing will determine the amplification of the input signal. Based on the input voltage selection, PSoC Creator will determine the sizing automatically and use them. As there are limited set of input & feedback capacitors available only certain gain factors are available.