Power supply monitoring

Power monitor solutions are available in the device, in order to survey the VDD (battery voltage).

Power supply supervisor

The power supply supervisor enables monitoring of the connected power supply.

Two functionalities are implemented:
  • Power-on reset (POR): Generates a reset when the supply is applied to the device, and ensures that the device starts up in a known state
  • Brownout reset (BOR): Generates a reset when the supply drops below the minimum voltage required for safe operations
Two BOR levels are used:
  • VBOROFF, used in System OFF
  • VBORON, used in System ON

The power supply supervisor is illustrated in the image below.

Figure 1. Power supply supervisor
Power supply supervisor

Battery monitoring on VDD

A battery voltage (VDD) monitoring capability is provided via a modem API

Note: For details regarding the modem API, please refer to nRF Connect SDK document and nRF91 AT Commands, Command Reference Guide document.

Registers

Electrical specification

Device startup times

Symbol Description Min. Typ. Max. Units
tPOR

Time in power-on reset after VDD has reached 3V, ENABLE is tied to VDD.

1.2 ms
tPINR

The maximum time taken to pull up the nRESET pin and release reset after power-on reset. Dependent on the pin capacitive load (C)1: t=TRC; Typical: T=2 R=13 kΩ; Max: T=5 R=16 kΩ.

.. .. ..  
tPINR,500nF

C=500 nF

13 40 ms
tPINR,10uF

C=10 µF

260 800 ms
tR2ON

Time from reset to ON (CPU execute)

127 µs
tOFF2ON

Time from OFF to CPU execute

73 µs
tWFE2CPU

Time from WFE to CPU execute

70 µs
tWFI2CPU

Time from WFI to CPU execute

69 µs
tEVTSET,CL1

Time from HW event to PPI event in constant latency System ON mode

0.1 0.1 µs
tEVTSET,CL0

Time from HW event to PPI event in low power System ON mode

0.1 0.7 µs
tLTEMODEM,TYP

LTE modem typical startup time. Time from application core powering up the modem until the modem is ready to receive the first AT command.

200 ms
tLTEMODEM,WORSTCASE

LTE modem worst case startup time. Time from application core powering up the modem until the modem is ready to receive the first AT command, with modem FW variable elements included.

250 ms
tLTEMODEM,FOTA

LTE modem startup time after modem FOTA update. Time from application core powering up the modem after a modem FOTA update until the modem is ready to receive the first AT command.

7.5 s
tLTEMODEM,FOTAREJECT

LTE modem startup time after a rejected modem FOTA update. Time from application core powering up the modem after a rejected modem FOTA update until the modem is ready to receive the first AT command. Modem will revert back to original FW image.

90 s
tLTEMODEM,STOP,TYP

LTE modem typical shutdown time. Time from application core calling bsd_shutdown command until bsd_shutdown returns.

1.6 s
tLTEMODEM,STOP,WORSTCASE

LTE modem worst case shutdown time. Time from application core calling bsd_shutdown command until bsd_shutdown returns, with modem FW variable elements included.

79 s

Power supply supervisor

Symbol Description Min. Typ. Max. Units
VBOR

Brownout reset voltage threshold.

2.00 V
VPOR

Voltage threshold at which the device enters power-on reset (POR) when VDD is ramping up.

2.15 V
1 To decrease the maximum time a device could be held in reset, a strong external pull-up resistor can be used.