• @user111953 ...take a look at this https://devzone.nordicsemi.com/f/nordic-­q-a/17668/gpio-high-drive-on-nrf52-any-l­imitations - points to the page with the attached graph. The higher the load in [mA], the higher the electromotive force compared to the ground in [volts]. The device is not strong enough to pull it to 'real' ground on sinking. Similar to sourcing: The higher the current in [mA] the lower the electromotive force on the pin. Therefore, the GPIO max current is usually specified so that the output voltage is still safely in the 0 and 1 logic ranges (incl with some noise). So much with 'static' load - switching frequency and thus also capacitance and other ...ances do not matter (yet). You can then calculate the dissipation yourself and know when you get into the zone of frying things that don't even show smoke when turning 'crispy'.

    Multiple factors play in to the limit, last but not least what is the voltage level you expect at the pad. Total dissipation is for sure defining the absolute cap and high average load has other impacts on the device.

    In an exercise - GPS powered by Espruino pin(s)- I successfully powered a now pretty outdated and power hungry GPS by Espruino pins. I used the PICO which is for sure quite a different device, but experienced principles there apply here as well. Somethin not to forget is that the PICO has no RF, and RF adds a lot to dissipation challenges.

    When you look at bangleJS hardware, pins do not directly drive loads. They either
    drive a (FE)Transistor or the enable pin of LDOs, which is a superb way to control power...

    1 Attachment

    • nrf52gpioCurrentVsVoltage.png

Avatar for allObjects @allObjects started