Timeline for Pic32MZ microcontroller ADC input scan causes voltage drop on sense pin
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 16, 2022 at 3:29 | answer | added | Kuba hasn't forgotten Monica | timeline score: 1 | |
| Mar 16, 2022 at 0:06 | comment | added | Ilya | @AhmetAtcı add your conclusions/observations as your own reply below and select it as a chosen answer. Glad you got it fixed. | |
| Mar 15, 2022 at 22:49 | comment | added | Ahmet Atcı | Thanks everyone adding a small cap solves problem everywhere with resistor divider and opamp output. I guess instant switching of adc scan creates current rush to the sample cap. And adding a cap to the input solves problem. Thanks. | |
| Mar 15, 2022 at 22:00 | comment | added | Kevin White | Just add a small capacitor at the input of the MCU to supply the charge needed for the input sampling capacitor. Maybe 1000pF. | |
| Mar 15, 2022 at 21:58 | comment | added | Kartman | What happens if you put a 10nF cap on the adc input? Assuming your inputs are low frequency? | |
| Mar 15, 2022 at 21:56 | history | edited | Kartman | CC BY-SA 4.0 |
Spellink
|
| Mar 15, 2022 at 21:51 | comment | added | Ilya | 1M-200k is crazily much. Even if you have a pair of picofarads of input capacitance, you have a whole RC circuit with massive resistor. Try making op amp buffer (voltage follower) and feeding it directly into input pin without any resistor and see what happens | |
| Mar 15, 2022 at 21:07 | comment | added | Ahmet Atcı | When using resistor divider i get that noise 352mVpp with 1M-200K resistor values. But when i use opamp with 50 ohm serial resistor I get 150mVpp peak. Problem still same with opamp. | |
| Mar 15, 2022 at 21:02 | comment | added | Klas-Kenny | Every time the ADC samples, the pin will draw some current to charge the internal capacitor of the sample-and-hold circuit. What series resistance do you have on the inputs? | |
| S Mar 15, 2022 at 21:00 | review | First questions | |||
| Mar 15, 2022 at 22:15 | |||||
| S Mar 15, 2022 at 21:00 | history | asked | Ahmet Atcı | CC BY-SA 4.0 |