Quectel SG865W Series Hardware Design page 45

BAT_ID
SMB_THERM
SMB_STATUS
SMB_EN_CHG
USB_IN_MID
The module supports battery temperature detection in the condition that the battery integrates a
thermistor (100 kΩ 1 % NTC thermistor with a B-constant of 4050K by default); and the thermistor is
connected to BAT_THERM pin, If the BAT_THERM pin is not connected, there will be malfunctions such
as battery charging failure, battery level display error, etc.
A reference design for the battery charging circuit is shown below.
Mobile devices such as mobile phones and handheld POS systems are powered by batteries. When
different batteries are utilized, the charging and discharging curve must be modified correspondingly to
achieve the best effect.
If the 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 mistakenly judge that the battery
temperature is abnormal, which will cause battery charging failure. In order to avoid this, BAT_THERM
should be connected to GND via a 100 kΩ resistor. If BAT_THERM is unconnected, the system will be
SG865W_Series_Hardware_Design
15 AI Battery type detect
SMB1390 parallel charging
28 AI
temperature detect
SMB1390 parallel charging
17 DI
status indicator
SMB1390 parallel charging
23 DO
enable
489, 490,
Power output for SMB1390
493, 494, PO
parallel charging
498
VBAT
NTC
GND
Battery
Figure 3: Reference Design for Battery Charging Circuit
Adapter or USB
C1 C2 C3
D1
100 μF
1 μF
ESD 33 pF
Smart Module Series
Parallel charging is not
supported by default.
If parallel charging is not
needed, keep these pins
open.
USB_VBUS
VBAT
BAT_P
BAT_THERM
BAT_M
VBAT_SNS_M
GND
Module
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