Quectel SC66 Hardware Design page 52

VBAT
NTC
GND
Battery
VBAT
NTC
GND
Battery
Figure 12: Reference Design for Battery Charging Circuit
SC66 offers a fuel gauge algorithm that is able to accurately estimate the battery's state by current and
voltage monitor techniques. Using precise measurements of battery voltage, current, and temperature,
the fuel gauge provides a dependable state of charge estimate throughout the entire life of the battery and
across a broad range of operating conditions. It effectively protects the battery from over-discharging, and
also allows users to estimate the battery life based on the battery level so as to timely save important data
before completely power-down.
Mobile devices such as mobile phones and handheld POS systems are powered by batteries. When
different batteries are utilized, the charging and discharging curve has to be modified correspondingly so
as to achieve the best effect.
If thermistor is not available in the battery, or adapter is utilized for powering the module, then there is only
a need for VBAT and GND connection. In this case, the system may be unable to detect the battery,
which will cause power-on failure. In order to avoid this, VBAT_THERM should be connected to GND with
a 47KΩ resistor. BAT_PLUS and BAT_MINUS must be connected, otherwise there may be abnormalities
SC66_Hardware_Design
Smart LTE Module Series
Adapter or USB
USB _VBUS
VBAT
BAT_PLUS
BAT_THERM
BAT_MINUS
GND
D1 D2 C1 C2 C3
Module
ESD ESD 100uF 33pF
1uF
NM
Adapter or USB
USB _ VBUS
VBAT
BAT_PLUS
BAT_THERM
BAT_MINUS
GND
D1 D 2 C1 C2 C3
Module
ESD ESD 100 uF 33pF
1uF
NM
SC66 Hardware Design
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