SIM Tech SimCom SIM340, Проектирование аппаратного обеспечения

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SIM340 Hardware Design
SIM340_HD_V3.09 18.03.2009
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VDD_EXT
（
OUTPUT
）
V
IL
<0.2*VBAT
V
IH
>0.6*VBAT
1s > Pulldown >0.5s
Logout net about 2s to 8s
PWRKEY
（
INPUT
）
Figure 10: Timing of turn off system
3.4.2.2 Turn off SIM340 using AT command
You can use an AT command “AT+CPOWD=1” to turn off the module. This command will let
the module to log off from the network and allow the module to enter into a secure state and save
data before completely disconnecting the power supply.
Before the completion of the switching off procedure the module will send out result code:
NORMAL POWER DOWN
After this moment, the AT commands can’t be executed. The module enters the POWER DOWN
mode, only the RTC is still active. POWER DOWN can also be indicated by VDD_EXT pin,
which is a low level voltage in this mode.
Please refer to
document [1]
for detail about the AT command of “AT+CPOWD”.
3.4.2.3 Over-voltage or under-voltage automatic shutdown
The module will constantly monitor the voltage applied on the VBAT, if the voltage ≤ 3.5V, the
following URC will be presented:
UNDER-VOLTAGE WARNNING
If the voltage
≥
4.5V, the following URC will be presented:
OVER-VOLTAGE WARNNING
The uncritical voltage range is 3.4V to 4.6V. If the voltage ≥ 4.6V or ≤ 3.4V, the module will
be automatic shutdown soon.