A/D specs

[danielh1]

Posted on December 03, 2003 at 06:30

A/D specs

[danielh1]

Posted on May 17, 2011 at 11:57

The following A/D important parameters are missing from the datasheet:

1 - Acquisition time. How long do we have to wait, after switching from one channel to another, before starting a reliable conversion? Worst case would be switching from 0V to 5V.

2 - Input impedance.

3 - Input leakage current.

I expect some answer from the ST staff.

[joseph2399]

Posted on May 17, 2011 at 11:57

Answers to your questions below:

1- There is no wait time needed after switching from one channel to another, before starting a reliable conversion. But for a reliable coversion, several conversion of same input point is need and the average value should be used.

2 - The input impedance on ADC is almost infinity.

3- There is no input leakage current. Please see the attached ADC block diagram.

[danielh1]

Posted on May 17, 2011 at 11:57

Quote:

1- There is no wait time needed after switching from one channel to another, before starting a reliable conversion. But for a reliable coversion, several conversion of same input point is need and the average value should be used.

Inaccurate, but it partially answers my question. The wait time is the time needed to charge the input capacitor. It depends on the output resistance of my circuit and on the value of this sample/hold capacitor, which is (min/max)?