What happens to nRF51822 if GPIO is set to source less current than required?

[Elias]

I have a board with some LEDs that are driven in the same way as with the nRF51 DK board (i.e. there is a resistor in series with the LED and you drive the pin low to turn the LED on). However, the series resistor has a lower value.

The datasheet for the non-Nordic board says that the LED pins must be configured to source 5mA. I didn't know this before I programmed the chip, so my program configured the pin to 0.5mA and tried to drive it low, and now I suspect the chip is fried.

I don't know much about the internal circuitry of a pin's drive strength option, so what happens if I have a pin to try to sink more current than is necessary? Is the current limited, or does the chip fry?

[Jørn]

Hello Elias Simon

There is no current limiting circuitry inside the chip. While sinking more current than the specification states is by no means optimal, it should be capable of doing it at least for a little while. Has the pin or chip failed to function properly after you did this? If it functions as it should, it is highly unlikely it took any damage.

Best regards

Jørn Frøysa

[Elias]

The chip seems to still be programmable. I'm using an nRF51 DK as a debugger and nRFgo Studio tells me whether the target is the nRF51422 (on the DK) or the nRF51822 (on the other board) as expected. Reading the program out also seems to work.

I left the GPIO toggling (on a human-visible scale) for several seconds. I can't toggle any GPIOs or do BLE advertising, even though I've confirmed the programs to work with the nRF51 DK.