Sigma-Delta ADC

Home

        Goto:   Calculations      Output Format        Notes

Definition:                           

Equation

Parameters

Diagram

Calculate Properties of a 1-bit ΣΔ ADC:              top

Parameter        

Value

Units

Note

Inputs:

R1 (feedback resistor) Note:  An alternate version includes 2 more resistors to change range
R2 (input resistor)  
FClk (uC clock frequency)  
N (#bits in sample)    
  Vdd (uC supply)    
           

Outputs:

VMax (max. input voltage) 

VMin (min. input voltage)

  VRange  (|VMax-VMin|)   =Vdd*R2/R1
  TS (sample period)    
  FS (sample rate)    
  FN (sample Nyquist freq.)

           
           

Output Format:                                                        top

Select Format: Scientific Engineering Fixed

Notes:                                                                       top

bullet

This calculator is for the case of a microcontroller (uC) digitizing an analog signal using the 1-bit Sigma-Delta (ΣΔ) approach.

bullet

You must keep C1=C2 when uC input threshold is at Vdd/2.

bullet

There may be chip-chip variations in input threshold level from an assumed Vdd/2.  So it may be wise to pick resistors that allow an input range greater than that required...  (For example, with R1=R2=100k a max. input of 3.3 volts is expected with the Propeller uC, however, this may not work and R2=150k is advised).

Copyright 2007  Raymond J. Allen