Figure 3.2.11.1 Battery protection circuit
3.2.11 Battery protection circuit
1. Battery protection board is installed on Li battery and used to prevent Li battery from being
damaged by short-circuit, over-charge and over-discharge. Li battery and battery protection board are
called as Li battery components. Battery protection board principle diagram is shown in the picture
3.2.11.1:
2. Working principle: battery protection circuit is mainly composed of battery protection IC S8261
and built-in dual N-channel MOSFET ECH8601. S8261 is the protection IC of Li-ion polymer changeable
battery of built-in high-precision voltage detect circuit and delay circuit. DOUT and COUT are over-
discharge (when Li battery voltage is lower than 2.4V) protection output end and over-charge (when Li
battery voltage is higher than 4.2V) protection output pin. When working normally, the two pins are high
level. MOSFET opens and Li battery voltage outputs to the player through protection board. When in
protection, the 2 pins output low level to control MOSFET to cut off power. Over-current detect (short-
circuit protection) is fulfilled by V- pin through detecting short-circuit state and controlling DOUT and
COUT output.
3.2.12 Power management module
1. Function of power management module is to provide 3.3V and 1.8V voltage for the player’s
normal working, shown in the picture 3.2.12.1, 3.2.12.2:
EN
U16
TPS79333 SOT 23-6
VIN
1
GND
2
EN
3
BYPASS
4
5
VOUT
C93
102
VCC
C91
106/X5R
C4
103
R98
68K
VCC
P_GND
P_GND
VB
P_GND
Figure 3.2.12.1 3.3V power circuit diagram
- 26 -