STM8L151K4 adc input impedance

dhutchison1945 · ‎2011-04-26

Posted on April 26, 2011 at 10:13

lowpowermcu · ‎2011-05-17

Posted on May 17, 2011 at 15:12

Hi spectre,

In the datasheet, I have found

RAIN: External resistance on VAIN. It is equal to 50 KOhm.

I think it the input impedance you are looking for.

dhutchison1945 · ‎2011-05-17

Posted on May 17, 2011 at 15:12

Dear lowpowermcu,

no,the rain(50kohm max) is the external resistor that you add in order to limitate the input current.

I want to know the adc input pin impedance,but I think that I can see only the leakage current.

b.r.

spectre

fggnrc2 · ‎2011-05-17

Posted on May 17, 2011 at 15:12

Hello Spectre!

I agree with you: I found only the leakage current which is mainly due to the internal ESD protection diodes.

You have also to take into account the current which the ADC draws in the sampling phase. This current depends on the input capacitance, whose value can be found in the datasheet too.

However, leakage current is usually a few microamps, so you can estimate ADC input resistance as one MOhm.

Regards,

EtaPhi