ENABLE (pin 101) is a high-impedance control pin for the nRF9160-internal PMU.
It is used to enable and disable nRF9160. Logic high (> 0.8 x VDD1) enables nRF9160. The start delay is in the range of a few milliseconds from pulling the ENABLE pin high. Logic low (< 0.4 V) disables nRF9160 and brings it into extremely low current consumption.
In products where nRF9160 is always enabled, the ENABLE pin can be connected to VDD1 (pin 102) on the application board with a series resistor. The series resistor minimizes digital noise coupling between the VDD1 and ENABLE pins. It is recommended to add a decoupling capacitor to the ENABLE pin. If ENABLE is connected to VDD1, a shared capacitor can be used for the ENABLE and VDD1 pins if the VDD1 decoupling capacitor is located close to the VDD1 and ENABLE pins.