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Re: ADC input impedance?

PostPosted: Tue Jan 31, 2017 2:32 am
by g6ejd
Yes, ADAFruit has not added a resistance divider do direct ADC input. The input leakage current of 50nA sounds correct so 20Mohms can't be far out.

Re: ADC input impedance?

PostPosted: Tue Jan 31, 2017 12:37 pm
by schufti
regarding the impedance of Tout:
http://bbs.espressif.com/viewtopic.php? ... ance#p3135
that is the only "official" statement I ever saw.

but you could check for yourself: just take a stable voltage source (<=1V) with low impedance and connect it via trim-pot (~2MOhm) to Tout.
Start with a setting of 0Ohm and get an averaged stable reading, then increase the value until your get half of your first reading. Now the set resistance correlates to the input impedance of the adc.

Re: ADC input impedance?

PostPosted: Tue Apr 18, 2017 2:33 pm
by temoto
cerebrate wrote:Quick question, if I may - is the input impedance, or maximum input current, of the ESP8266-12 ADC pin documented anywhere? I haven't been able to find it in any of the spec sheets I've dug up.

Thanks in advance,

-c


> The input impedance of the ADC is very high, in the range of 1MΩ.
Source: http://bbs.espressif.com/viewtopic.php?t=909

Re: ADC input impedance?

PostPosted: Thu Apr 20, 2017 2:21 am
by cerebrate
temoto wrote:> The input impedance of the ADC is very high, in the range of 1MΩ.
Source: http://bbs.espressif.com/viewtopic.php?t=909


Thanks, much appreciated!

-c