nRESET (pin 9) is a dedicated nRF9151 reset pin. nRF9151 reset is generated on the falling edge when the nRESET pin is pulled low and released on the rising edge. Keep the nRESET pin low for at least 5 µs to ensure the reset is issued correctly.
If nRESET is held low while nRF9151 powers up, code execution starts once VDD and ENABLE are high.
The nRESET pin has a 13 kΩ internal pull-up resistor that is always on and connected to the nRF9151 internal voltage of 2.2 V. The nRESET pin can be connected to an external controller or mechanical switch that is controlled by the user. It is recommended to add a bypass capacitor and series resistor in the range of 1 kΩ to the nRESET routing. For more information on pin reset, see Reset in nRF9151 Product Specification.
- External pull-up is not allowed in the nRESET pin.
- External filtering components affect the minimum pulse length.
PCB layout design
When designing the PCB layout, consider the following recommendations for the nRESET pin:
- Place bypass capacitor C8 close to the nRESET pin 9.
- For debugging purposes, consider adding access to nRESET line in final product.