nRF52 maximum capacitive load on GPIO pins

RE: nRF52 maximum capacitive load on GPIO pins

Otso Jousimaa — Wed, 29 Apr 2020 09:17:16 GMT

Ok, Thanks. We'll consider charging any capacitors safe

RE: nRF52 maximum capacitive load on GPIO pins

Jared — Wed, 29 Apr 2020 09:06:00 GMT

Hi,

The current will be limited by the nRF, which in effect will increase the charging time of the capacitor. There is no specified limit on how much capacitance you can place on the GPIO pins.

regards

Jared

RE: nRF52 maximum capacitive load on GPIO pins

Otso Jousimaa — Tue, 28 Apr 2020 12:04:33 GMT

[quote userid="18935" url="~/f/nordic-q-a/60783/nrf52-maximum-capacitive-load-on-gpio-pins/247077"]Nope. The GPIOs are current limited - ~4mA in standard drive and ~20mA in high drive.[/quote]

Can you point me to a section of datasheet which says it's safe to short-circuit GPIO because of this current limit? If not, there must be some limit to the load on GPIO. I'd prefer to find the limit in some other manner than having end-users report failures under some conditions or after some time.

RE: nRF52 maximum capacitive load on GPIO pins

Turbo J — Tue, 28 Apr 2020 11:41:42 GMT

[quote userid="68002" url="~/f/nordic-q-a/60783/nrf52-maximum-capacitive-load-on-gpio-pins"] In theory there would be infinite current spike when the capacitors start charging from 0 V to VDD[/quote]

Nope. The GPIOs are current limited - ~4mA in standard drive and ~20mA in high drive.

If possible, I'd use standard drive for the initial ramping, and then switch to high drive. This way one could charge an arbitrary sized capacitor given a VCC source with more than 5mA current.

Note: A CR2032 has trouble delivering this much current at rated voltages and would need at least some large capacitors "helping" out.