https://devzone.nordicsemi.com/f/nordic-q-a/27357/nrf52840-saadc-real-impedance-4-7kHi Engineers! faced with a problem of SAADC impedance too small (4,7K)! We use SINGLE ENDING 8bit mode with following settings: NRF_SAADC_REFERENCE_VDD4 NRF_SAADC_GAIN1_4 NRF_SAADC_RESISTOR_DISABLED NRF_SAADC_ACQTIME_40US ( 40us) en-USTelligent Community 13Fri, 17 Nov 2017 18:03:15 GMThttps://devzone.nordicsemi.com/thread/108036?ContentTypeID=1Fri, 17 Nov 2017 18:03:15 GMT137ad170-7792-4731-bb38-c0d22fbe4515:30892c78-3a33-48a8-a99b-2e3340ebad25AmbystomaLabs<p>There is no real input impedance associated with an SAADC. Most all utilize the same design of a switched capacitance on the input that they then use as the input voltage sample during the success approximation part.</p> <p>So your input model will be an exponential model and not a linear resistive model.</p> <p>Here is a little discussion on the subject: <a href="https://devzone.nordicsemi.com/question/82609/nrf52-adc-front-end-circuit/">devzone.nordicsemi.com/.../</a></p><div style="clear:both;"></div>