nRF52810 pin hardware architecture

[gschelotto]

Hi,

I'd need some information I'm not able to find in product specification v1.3:

• What is the architecture of the GPIO / AN pins of this device? Input protection diodes, pull-up/down, output open drain, push-pull, etc
• What is the state of the all pins during the power-up? For example pin4 of QFN48 package is a digital or an analog input?
  
• Can I configure any digital pin as MISO, MOSI, SCLK or CS?

thanks in advance,
gaston

[ketiljo]

What is the architecture of the GPIO / AN pins of this device? Input protection diodes, pull-up/down, output open drain, push-pull, etc

All pins have ESD protection diodes. All pins can have pull-up/down. Output is push-pull only

What is the state of the all pins during the power-up? For example pin4 of QFN48 package is a digital or an analog input?

During power up, all pins are disconnected, i.e. high Z.

Can I configure any digital pin as MISO, MOSI, SCLK or CS?

You can configure the digital interfaces to any pin. Only the analog inputs are fixed.

 

 

[Dmitry]

ketiljo said:

Output is push-pull only

AFAIK, open-drain configurations can be used as well (either P or N MOSFETs can be disconnected)

[ketiljo]

Yes, you're correct!

[gschelotto]

ketiljo said:

All pins have ESD protection diodes.

ketiljo said:

During power up, all pins are disconnected, i.e. high Z.

These are the points I'd need to clarify. ESD diodes are before or after the disconnected input?

My main concern is that in my application I have some uC pins tied to 4.5V (not the uC main 3V3 power supply ) and when the uC is OFF I need to avoid this picture:

Could you confirm this?

gaston

[Dmitry]

ESD diodes are placed at pin entry - they protect a circuit regardless of its state.

In your case, you will have voltage above VDD+0.3 at your pin that may cause damage of uC. Is there any specific reason to tie 470k to 4.5V, not Vcc?

[ketiljo]

The ESD diodes are always present. Max voltage on any GPIO pin is VDD+0.3 V. So in the case when VDD = 0 V, max voltage o the pin is 0.3 V. Else you will back power the device via the GPIO and the ESD diode. 

But given that you have a 470 kohm pullup resistor, this will limit the current to (4.5 - 0.3) / 470k = 9 µA. 

This is safe so you're ok here.