Sampling Frequency of Dual ADC

Answer:

Question:  How to adjust the sampling frequency of a Dual ADC?

 

Response:  In order to get the exact sampling frequency, data clock and the calc time needs to be adjusted. For example,

 

CPU Frequency = 24MHz

Required Sample Rate = 3200SPS

Resolution = 8 bits

 

Data Clock = Sample Rate * (2^(No.Of Bits +2) + Calc Time)

 

Assuming Calc Time of 0

Data Clock = 3200 * 2^10 = 3.2768MHz

 

Selecting SysClk*2 as VC3 source, the nearest divider is 14. The resultant Data clock is 3.4285MHz.

 

Now calculate minimum Calc time

 

Calc Time = Data Clock * 260 / CPU Clock

Calc Time = 3.4285MHz * 260 / 24MHz = 37

 

Now by adjusting the Calc Time parameter exact sampling frequency can be obtained.

 

Sampling Frequency = Data Clock / (2^10 + Calc Time)

 

If the Calc Time as 47, then the sampling frequency is 3201.2 SPS.