ADC conversion time

jeyakumar · ‎2008-04-13

Posted on April 13, 2008 at 18:15

ADC conversion time

jeyakumar · ‎2011-05-17

Posted on May 17, 2011 at 12:29

Dear Friends,

How to caculate ADC conversion time based upon clock.Because conversion time differed by clk.It was mentioned in datasheet for Example

Freq: 56 MHZ -1 us

72 MHZ -1.17us

pls explain and give the formula for this calculation

Thank you

16-32micros · ‎2011-05-17

Posted on May 17, 2011 at 12:29

This is very easy. One channel ADC conversion time takes APB 14 cycles,

with a maximum clock entry of 14MHz to the analog part. so depending on your ADC prescaler then APB to CPU clock ratio you will get the formula. 56 is a multiple of 14 so the calculation is easy and you get 1Âµs. You can also use both ADCs and you can reduce this conversion time to 500ns only. I suggest you to get a look on RM0008 document , then ADC section for more details.

Cheers,

STOne-32.

jeyakumar · ‎2011-05-17

Posted on May 17, 2011 at 12:29

Thank you for your immediate reply

your point is

If we are working on 56MHZ

Adc clock =56MHz(CPU clock)/((ADC Prescalar)4)=14MHz

But If we are working on 72MHz

Adc clock =72MHz(CPU clock)/(((ADC Prescalar)6)=12MHz

Because of changes in ADC clock frequency differences are there in ADC conversion time.

Note:

1.ADC prescalar dividers values are ->2,4,6,8

2.500ns conversion time is possible only in if we have two ADC's using the method of Dual sampling.

Pls check this and let me know if i made any mistake in this.

Thank you

Warm Regards,

Jeyakumar.R

16-32micros · ‎2011-05-17

Posted on May 17, 2011 at 12:29

I believe that you find it out :) this time.