nRF52832 chip off but GPIO receives power, will this cause damage?

[klm19]

Hi there,

We have designed our circuit board with the nRF52832 chip. One of the GPIOs is used to monitor a 12V power supply. We use a voltage divider on the 12V so the Nordic is monitoring a 3.3V output. Upon startup, the 12V power supply will be on a few seconds before the 3.3V to the Nordic, the Nordic will momentarily be receiving voltage and current to the GPIO while it is off. We are wondering if this will damage the GPIO pin on the Nordic. We can't seem to find any specs for this scenario, what range of current can the GPIOs handle while chip is off. Does the current have to be in the micro amps? Thanks in advance for your help!

[Håkon Alseth]

Hi,

 

By applying 3.3V to a GPIO when the VDD_nRF = 0V, you are exceeding the absolute maximum ratings (for I/O pin voltage):

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/abs_max_ratings.html?cp=2_1_0_4#abs_max_ratings

What will happen is that the ESD protection inside the pad will open, thus the chip will try to start up. A voltage divider is likely not able to provide enough current, so the voltage will likely have a saw-tooth form. I will strongly recommend that you apply VDD_NRF first, then the voltage divider.

 

Kind regards,

Håkon

[awneil]

Håkon Alseth said:

What will happen is that the ESD protection inside the pad will open, thus the chip will try to start up. A

klm19 - Note that this is pretty much standard for any chip - not specific to Nordic.