Monitor The Power Supply; Power-On/Off Scenarios; Turn On With Pwrkey - Quectel EC21 Series Hardware Design

to provide sufficient current up to 2.0 A at least. If the voltage drop between the input and output is not
too high, it is suggested that an LDO should be used to supply power for the module. If there is a big
voltage difference between the input source and the desired output (VBAT), a buck converter is preferred
to be used as the power supply.
The following figure shows a reference design for +5.0 V input power source. The typical output of the
power supply is about 3.8 V and the maximum load current is 3.0 A.
DC_IN
470 μF 100 nF
NOTE
To avoid damaging internal flash, do not switch off the power supply when the module works normally.
Only after the module is shut down by PWRKEY or AT command, then the power supply can be cut off.

3.6.4. Monitor the Power Supply

AT+CBC can be used to monitor the VBAT_BB voltage value. For details of the command, see
document [2]..

3.7. Power-on/off Scenarios

3.7.1. Turn on with PWRKEY

The following table shows the pin definition of PWRKEY.
EC21_Series_Hardware_Design
MIC29302WU
2
IN
51K
4.7K
VBAT_EN
47K
Figure 9: Reference Circuit of Power Supply
LTE Standard Module Series
4
OUT
100K
1 %
470R
47K
1 %
VBAT
470 μF
100 nF
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