User's Guide

LE920A4 HW User Guide Hardware Commands
Doc#: 1VV0301261 Turning off the Module
Rev. 4.7.1 Page 51 of 124 2019-11-21
5.3.3. Unconditional Hardware Shutdown via SHDN Pad
To unconditionally shut down the module, the SHDN_N pad must be tied low for at least
200 milliseconds and then released.
A simple circuit for applying unconditional shutdown is shown below:
Figure 7: Circuit for Unconditional Hardware Shutdown
The system power down timing for using SHDN_N is shown below
Figure 8 Power down timing using SHDN_N
NOTE:
Do not use any pull-up resistor on the SHDN_N line or any totem pole digital
output. Using a pull-up resistor may cause latch-up problems on the module’s
power regulator and improper functioning of the module. The SHDN_N line
must be connected only in an open-collector configuration.
NOTE:
The Unconditional Hardware Shutdown must always be implemented on the
boards, but the software must use it only as an emergency exit procedure, and
not as a normal power-off operation.
200mS Sec < T_Hold
VBATT
SHDN_N
SW_RDY
T_RDY ~0 Sec
V_AUX
PWRMON
T_PWRMON ~0 Sec
OFF StateActive State