Power monitor solutions are available in the device, in order to survey the VDD (battery voltage).
The power supply supervisor enables monitoring of the connected power supply.
The power supply supervisor is illustrated in the image below.
The external power failure (EXTPOF) warning can provide the CPU an early warning of an imminent power failure. It does not reset the system, but gives the CPU time to prepare for an orderly power-down. EXTPOF detects power failures external to PMU from the device internal PMIC.
The user can start and stop the PMIC EXTPOF feature and set the battery voltage low threshold level through the modem API.
For application core to receive the power failure warning events, EXTPOFCON register in REGULATORS — Voltage regulators control must be enabled. If this is disabled, the state of the PMIC warning input is ignored and the power failure warning events are not delivered to application core.
The available time for the CPU to prepare for a power-down depends on the set warning threshold level, the load of the running tasks, and the type of power source used.
The EXTPOF functional overview is shown in the following figure.
If EXTPOF is enabled and the device's internal PMIC detects that battery voltage has dropped below the low threshold level, an POFWARN event is generated (see EVENTS_POFWARN). The POFWARN event to the CPU can be cleared in the event register, however the PMIC input continues to indicate a warning as long as the battery voltage remains below the low threshold level.
POFWARN event also sets the LTE modem in offline mode.
The external power failure warning doesn't trigger wakeup from System OFF.
The external power failure warning is disabled in System OFF mode.
A battery voltage (VDD) monitoring capability is provided via a modem API.
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 | 135 | µs | |
tOFF2ON |
Time from OFF to CPU execute |
73 | 92 | µs | |
tWFE2CPU |
Time from WFE to CPU execute |
70 | 90 | µs | |
tWFI2CPU |
Time from WFI to CPU execute |
69 | 90 | 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 firmware 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 firmware 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, including modem firmware variable elements. |
79 | s |
Symbol | Description | Min. | Typ. | Max. | Units |
---|---|---|---|---|---|
VBOR |
Brownout reset voltage threshold. |
2.80 | V | ||
VPOR |
Voltage threshold at which the device enters power-on reset (POR) when VDD is ramping up. |
3.0 | V |