V_Bckp - Quectel L76 Hardware Design

GNSS Module Series
Module
VCC
PMU
TVS
10 µF 100 nF 33 pF
ESD5651N
Figure 4: VCC Input Reference Circuit

3.2.2. V_BCKP

The V_BCKP pin supplies power for the RTC domain. If the module power supply fails, the V_BCKP pin
supplies power for the real-time clock (RTC) and RAM. Use of valid time and GNSS orbit data at startup,
allows GNSS hot (warm) start. If no backup power is connected, the modules perform a cold start at
power up.
If there is a constant power supply in your system, it can be used to provide a suitable voltage to power
V_BCKP.
V_BCKP can be directly powered by an external battery (rechargeable or non-rechargeable). It is
recommended to place a battery with the combination of a 4.7 μF, a 100 nF and a 33 pF capacitor near
the V_BCKP pin. The figure below illustrates the reference design for supplying power for the RTC
domain with a non-rechargeable battery.
Module
V_BCKP
RTC
Domain
Non-
rechargeable
4.7 μF
100 nF
33 pF
Backup Battery
Figure 5: RTC Powered by Non-rechargeable Battery
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