ADACK Setup

[benatar]

Hi,

Im trying to understand how is the value of ADACK calculated.

Im using the Asynchronous mode for clocking the ADC (ADICLK=11) and ADIV=11 (divide by 8).

The core clock runs at 120Mhz.

Thanks,

Ben.

[benatar]

Hello Mario,

Thanks for replying.

I am using the app. sample in the SDK marked as adc16\polling as the base for testing the ADC.

The board is a customized K22FN512 based board.

In order to post process the samples (FFTs etc.) i need to know the exact sampling rate, so the range, as an example of 3Ms to 7.3Ms is not accurate enough.

Thanks,

Ben.

[mario_castaneda]

Hi ben

The sampling rate in asynchronous mode, could change depending of a lot of factors, for example the temperature, but if you want to calculate the exact sampling rate, I recommend you to use the bus clock for conversion time.

Let me know if you have problems with the conversion time

Hope it helps

Mario

[mario_castaneda]

Hi Ben

Which board are you using?

For example if you are using the FRDM K64F you can check the datasheet document chapter 3 ADC Electrical Characteristics

As you can see the frequency depends of the configuration of the ADLPC register CFG1 and ADHSC register CFG2.

And if you want to calculate the ADC time conversion you can check the following equation,

The equation is explained in the reference manual, 35.4.4.5 Sample time and total conversion time, explains how to calculate the time and the possible options, for ADC conversions cycles.

http://www.nxp.com/files/microcontrollers/doc/ref_manual/K64P144M120SF5RM.pdf?fpsp=1&WT_TYPE=Referen...

Let me know if you have problems with the asynchronous clock source

Hope it helps

Mario