Vrtc Interface - Quectel Smart Wi-Fi Module Series User Manual

3.5.

VRTC Interface

The RTC (Real Time Clock) can be powered by an external power source through VRTC when the
module is powered down and there is no power supply for the VBAT. The external power source can be
capacitor, rechargeable battery or non-rechargeable battery according to application demands. The
following are some reference circuit designs when an external battery or capacitor is utilized for powering
RTC.
If RTC is ineffective, it can be synchronized when the module starts data connection after power on.
Rechargeable
Backup Battery
Large
Capacitance
Capacitor

2.0~3.25V input voltage range and 3.0V typical value for VRTC. When VBAT is disconnected, the
average consumption is 5uA.

When powered by VBAT, the RTC error is 50ppm. When powered by VRTC, the RTC error is
200ppm.

If the rechargeable battery is used, the ESR of the battery should be less than 2K, and it is
recommended to use the MS621FE FL11E of SEIKO.

If a large capacitance capacitor is selected, it is recommended to use a 100uF capacitor with low
SC20-W_Manual_R1.0
Figure 6: Timing of Turning off Module
Figure 7: RTC Powered by Rechargeable Battery
C
Figure 8: RTC Powered by Capacitor
Confidential / Released
VRTC
Module
VRTC
Module
RTC
Core
RTC
Core
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