User's Manual

LE940B6 Hardware User Guide

1VV0301331 Rev. 1.8 - 2017-03-15

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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

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.