User's Guide

LM940 HW Design Guide
1VV0301352 Rev. 2 Page 36 of 68 2017-07-19
Information – To avoid a back-powering effect, it is recommended to
avoid having any HIGH logic level signal applied to the digital pins of
the module when it is powered OFF or during an ON/OFF transition.
Shutdown by Software Commnad
FinalizationState OFFState
InternalState
VREG_L6_1P8
VPH_PWR
ActivationState
AT#SHDN
VariableAbove
TBDsec
MonitoringStatus
W_DISABLE_N
MustBeAssertedLow.
Unconditional Hardware Reset
To unconditionally restart the LM940 module, the SYSTEM_RESET_N pin must be
asserted low for a between 100 milliseconds and 150milliseconds then released.
Below figure shows a simple circuit for this action.
Circuit for Unconditional Hardware Reset
GND
R1
R2
Q1
Unconditional
ResetImpulse
100 ms<HoldTime<150ms
SYSTEM_RESET_N
Information – The Unconditional Hardware Reset must be used only
as an emergency exit procedure, and not as a normal power-off
operation.