nRF52840 Open Drain GPIO

[Terry Tan]

nRF52840  SDK 15.2

I want to control the power of sensor, so I configurate the pin like this:

nrf_gpio_cfg(AFE4403_PIN_PWR_EN,
                 NRF_GPIO_PIN_DIR_OUTPUT,
                 NRF_GPIO_PIN_INPUT_DISCONNECT,
                 NRF_GPIO_PIN_NOPULL,
                 NRF_GPIO_PIN_S0D1,
                 NRF_GPIO_PIN_NOSENSE);

When I intended to power off the senser, code as below:

 nrf_gpio_pin_set(AFE4403_PIN_PWR_EN); // Power off senser

But I can't close the CMOS, means that measure the D pin of CMOS and voltage is not zero, equal VBat.

Measure the G pin of CMOS, the voltage equal 3.4V.

I don't understand where is my mistake about the code of configuration, could you help me?

[Turbo J]

There is a diode between GPIO pin and VCC in he NRF chip -  see absolute maximum ratings.

This will prevent the gate voltage to get close enough to source, and the mosfet will stay open.

[Terry Tan]

I find this "https://devzone.nordicsemi.com/f/nordic-q-a/28373/nrf52810-open-drain-gpio",. I understand it! If the gpio is higher than VDD+0.3V, the pull up will auto turn on, so the S0D1 is quasi open drain. 

[PKSHER]

hi. I am also working on a similar thing. Just wanted to know what solved your issue?

Regards

[Terry Tan]

Hi, You have to use VDD, don't use VDDH, because this is chip mistake. Voltage of VBAT must equal the GPIO_pin