S32k144 ADC conversion and sampling time

[sarwath]

Hello Community,

I am using S32K144 EVB , how to calculate the conversion and sampling time. My ADC operating frequency is 40MHZ.

BR,

Sarwath

[VaneB]

Hi @sarwath 

Please refer to character 44.5.4.5 "Sample time and total conversion time" of the S32K1xxRM.
Also the application note AN12217: S32K1xx ADC guidelines, spec and configuration, could be useful for you, this presents information of basic topics to get the most benefit from the use of the ADC module.

B.R.

VaneB

[sarwath]

Hello @VaneB ,

I read the RM and I found the adc total conversion formula.

ADC TOTAL CONVERSION TIME = Sample Phase Time (set by SMPLTS + 1) + Hold
Phase (1 ADC Cycle) + Compare Phase Time (8-bit Mode = 20 ADC Cycles, 10-bit
Mode = 24 ADC Cycles, 12-bit Mode = 28 ADC Cycles) + Single or First continuous
time adder (5 ADC cycles + 5 bus clock cycles).

My SMPLTS = 12 , Bus clk freq =40MHZ and ADC clk freq =40 MHZ.

one Bus cycle =1/bus clk freq =1/40MHZ =25ns

one Adc cycle=1/ADC clk freq =1/40MHZ =25ns

ADC TOTAL CONVERSION TIME= (12+1)+1 ADC cycles +28 ADC cycles+5 ADC cycles +5 bus clock cycles

                                                       = 47 adc cycle + 5 bus cycle.

                                                       =47 * 25 ns + 5 * 25ns

                                                       =1300 ns (~1.3 millisecond)

My total ADC conversion time is 1.3 millisecond. is this correct ?

How to understand the sampling rate ( my SMPLTS is 12).

BR,

Sarwath

[VaneB · Accepted solution]

Your ADC TOTAL CONVERSION TIME  = 1300 ns = 0.0013 ms

and sampling rate = 1/(SMPLTS * ADC Cycle) = 1/(12 * 25 ns)  ≃ 3.33 MHz

[sarwath]

Thanks @VaneB . Now I am clear about this conversion and sampling rate.

[sarwath]

Hello @VaneB ,

How to calculate correct the sample time in ADC config. Because it is affect my adc output.

Thanks in advance,

Sarwath