Summary Of State Transition; Rtc Backup; M35_User_Manual - Quectel M35 User Manual

3.5.4. Summary of State Transition

Table 6: Summary of State Transition
Next Mode
Current Mode
Power Down
Power Down
AT+QPOWD, use PWRKEY
Normal Mode
pin, or use EMERG_OFF pin
Use PWRKEY pin, or use
SLEEP Mode
EMERG_OFF pin
3.6.

RTC Backup

The RTC (Real Time Clock) function is supported. The RTC is designed to work with an internal power
supply.
There are three kinds of designs for RTC backup power:

Use VBAT as the RTC power source.
When the module is turned off and the main power supply (VBAT) is remained, the real time clock is still
active as the RTC core is supplied by VBAT. In this case, the VRTC pin can be kept floating.

Use VRTC as the RTC power source.
If the main power supply (VBAT) is removed after the module is turned off, a backup supply such as a
coin-cell battery (rechargeable or non-chargeable) or a super-cap can be used to supply the VRTC pin to
keep the real time clock active.

Use VBAT and VRTC as the RTC power source.
As only powering the VRTC pin to keep the RTC will lead an error about 5 minutes a day, it is
recommended to power VBAT and VRTC pin at the same time when RTC function is needed. The
recommended supply for RTC core circuits are shown as below.

M35_User_Manual

Normal Mode
Use PWRKEY
Pull DTR down or
incoming voice call or
SMS or data call
Confidential / Released
GSM/GPRS Module Series
M35 User Manual
Sleep Mode
Use AT command
―AT+QSCLK=1‖ and pull
DTR up
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