Product Info

LTE Module Series
EC21 Hardware Design
EC21_Hardware_Design
3-35
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Figure 9: Reference Circuit of Power Supply
In order to avoid damaging internal flash, please do not switch off the power supply when the module
works normally. Only after the module is shut down by PWRKEY or AT command, the power supply can
be cut off.
3.5.4. Monitor the Power Supply
AT+CBC command can be used to monitor the VBAT_BB voltage value. For more details, please refer to
document [2].
3.6. Turn on and off Scenarios
3.6.1. Turn on Module Using the PWRKEY
The following table shows the pin definition of PWRKEY.
Table 7: Pin Definition of PWRKEY
Pin Name
Pin No.
I/O
Description
Comment
PWRKEY
21
DI
Turn on/off the module
The output voltage is 0.8V because of
the diode drop in the Qualcomm chipset.
When EC21 is in power down mode, it can be turned on to normal mode by driving the PWRKEY pin to a
low level for at least 500ms. It is recommended to use an open drain/collector driver to control the
PWRKEY. After STATUS pin (require external pull-up) outputting a low level, PWRKEY pin can be
released. A simple reference circuit is illustrated in the following figure.
NOTE