Smart Module Series
SC690A_Series_Hardware_Design 38 / 105
the battery temperature is abnormal, which will cause battery charging failure. To avoid this,
BAT_THERM should be connected to GND via a 10 k
Ω resistor. If BAT_THERM is unconnected, the
system will be unable to detect the battery, and the battery will not be charged.
BAT_P/M must be connected. Otherwise, the module will have trouble in voltage detection, as well as
associated power on/off issues and battery charging/discharging issues.
3.1.3. Reference Design for Power Supply
The power design for the module is very important, as the performance of the module largely depends
on the power source. The power supply of the module should be able to provide sufficient current of at
least 3 A. If the voltage drop between the input and output is not too big, it is suggested to use an LDO to
supply power for the module. If there is a big voltage difference between the input source and the
desired output (VBAT), a buck converter is recommended.
The following figure shows a reference design for +5V input power source. The designed output of the
power supply is about 3.8 V and the maximum rated current is 5 A.
VCC_5V
U1
PGND
PGND
PGND
PVIN
PVIN
PVIN
EN
SS/TR
SW
SW
SW
VOS
PG
FB
FSW
DEF
GND
3V8_EN
DC_3V8
D1
C1
C3
C2
R1
Q1
R2
R3
L1
R4
R5
R6
C5
C6
C4
470
μ
F
10
μ
F
100 nF
4.7 K
47K
51K
3.3
nF
2.2 uH
100 K
75 K
20 K
22
μ
F
100 nF
Figure 4: Reference Circuit of Power Supply
3.1.4. Requirements for Voltage Stability
The power supply range of the module is from 3.55 V to 4.4 V, and the recommended value is 3.8 V. The
power supply performance, such as load capacity, voltage ripple, etc. directly influences the modu
le’s
performance and stability. Under ultimate conditions, the module may have a transient peak current of
To avoid damaging internal flash, do not switch off the power supply when the module works normally.
Only after shutting down the module with PWRKEY or AT command can you cut off the power supply.
NOTE
