How to calculate ADC Sampling Rate

[soumen21]

According to datasheet, the ADC clock frequency should be
between 50kHz and 200kHz to ensure 10-bit effective resolution. 50kHz ADC clock frequency is chosen. Then the sampling frequency becomes ~3800 SPS.
Vref = 5V, Vin =2.5V

How the sampling frequency is calculated ?

 

[alexan_e]

I assume that you are asking for AVR.
The datasheet explains it in the ADC section, In ADCSRA register the bits 2-0 control the division factor

•  Bits 2:0 – ADPS2:0: ADC Prescaler Select Bits 

 These bits determine the division factor between the XTAL frequency and the input 
 clock to the ADC. 

 Table 76.    ADC Prescaler Selections 

        ADPS2                ADPS1                ADPS0                    Division Factor 

           0                    0                    0                             2 

           0                    0                    1                             2 

           0                    1                    0                             4 

           0                    1                    1                             8 

           1                    0                    0                            16 

           1                    0                    1                            32 

           1                    1                    0                            64 

           1                    1                    1                            128

Alex

 

[soumen21]

Hi Alex,
Thanks for your reply. Yes, it is for AVR. But I could calculate the approximate value as mentioned (~3800 SPS) in the application note using the divisor table. Can you please show me the calculation ?

 

[alexan_e]

you divide the clock with the division factor, for example 8000000/128=62500Hz
This frequency should be between 50000Hz and 200000Hz.
The normal conversion takes 13 cycles so the sample/sec is ADC frequency/13

Alex