LE940B6 HW User Guide
Rev. 2.02
Page 55 of 111
2020-01-10
5.3.4.
Unconditional Hardware Shutdown
To unconditionally shut down the LE940B6 module, the SHDN_N pad must be tied low for
at least 200 milliseconds and then released.
Figure 10 shows a simple circuit for applying an unconditional shutdown.
Figure 10: Circuit for Unconditional Hardware Shutdown
GND
R1
R2
Q1
Unconditional
Shutdown Impulse
At least 200ms
SHDN_N
To check whether the device has powered off, monitor the VAUX/PWRMON hardware
line. When VAUX/PWRMON goes low, the device has powered off.
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
LE940B6 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 (SHDN_N) 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.
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