nrf51822 GPIO direct source with high drive setting

[sosse]

I directly connect GPIO pin with 24ohm resistor as follows. And I set GPIO pin as high drive,

NRF_GPIO->PIN_CNF[MY_PIN_NO] |= (GPIO_PIN_CNF_DRIVE_H0H1 << GPIO_PIN_CNF_DRIVE_Pos);

When I measure the current, I got 38mA. But it should not exceed 15mA ? What am I wrong?

Thank you.

[Ole Bauck]

24ohm * 38 mA ~= 0.9V, so you see that the output voltage will fall if the current goes up. The specification says that you can draw 5mA in high drive and the voltage will still be within VDD-0.3 and VDD. We recommend that you draw no more than 15mA in total as Roger says, this can be from one pin. If you draw more than this we can't guarantee that the chip will function properly.