ADC convertion time

leonhard · ‎2009-12-02

Posted on December 02, 2009 at 09:44

ADC convertion time

leonhard · ‎2011-05-17

Posted on May 17, 2011 at 13:32

I already started with ADC of STM32

How can I calculate the Sample Time (@72 MHz). How long is one cycle (1/72Mhz?)?

How do I chose the adequate samling time. I have to several different signals. Some motor currents (dc), some ntc's and some other more or less static currents.

sofiene · ‎2011-05-17

Posted on May 17, 2011 at 13:32

Hi leonhard;

In fact the maximum ADC clock allowed is 14MHz.

Choosing the sampling time depends strongly on your hardware i.e. it depends on the impedance of the source (RAIN) you are converting. In fact RAIN should meet the condition (formula given in the datasheet: ''12-bit ADC characteristics''.

The total conversion time = sampling time + conversion time.

- Conversion time is equal to 12.5 ADC cyles.

- The sampling time is configured regarding the impedance condition. The higher impedance, the higher the sampling time (refer to the application note AN2834 ''How to get the best ADC accuracy in STM32F10xxx devices'')

B.R.

M3allem

armmcu · ‎2011-05-17

Posted on May 17, 2011 at 13:32

If I may intervene I will add:

In these calculations one cycle is an ADC clock cycle = 1/fADC

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