Teclast X21, Service Manual

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V
D
D
5
Ct
4
Vss
6
D
o
u
t
1
C
o
u
t
3
V-
2
U1
U2
B
R1
R2
C1
P+
P-
C2
C3
LITHIUM BATTERY
Figure 3.2.8.2 Battery protection circuit equivalent circuit schematic diagram
2. Working principle: battery protection circuit is mainly composed of battery protection IC S8261
and built-in dual N groove MOSFET ECH8601. S8261 is lithium-ion polymer of built-in high precision
voltage detect circuit and delay circuit, which may be served as protection IC of battery. DOUT and
COUT pin are over-discharge (when lithium battery voltage is lower than 2.4V, it is called over discharge)
protection output end and over-charge (when lithium battery voltage is higher than 4.2V, it is called over
charge) protection output end. When in normal condition, these two pins are high level, MOSFET
switches on, lithium battery voltage outputs to the player through protection board; when in protection,
these two pins output low level to control MOSFET and turn off power. Over-current detection (short-
circuit protection) is fulfilled through detecting short corcuit stat
cts that voltage on R2 increases instantly to control DOUT and COUT to output low level at the
same time and control MOS tube to cut off from battery to protect battery.
3.2.9 Power management module
1. Function of power management module is to provide the player with 3.3V, 3.8V and1.8V of
normal working. Circuit schematic diagram is shown in the figure 3.2.9.1, 3.2.9.2 and 3.2.9.3:
e by V- pin to control DOUT and COUT
output. When battery has short circuit, voltage on V- externally connected resistor has a sudden change,
V- dete
EN
U1
TPS79301 SOT 23-6
VIN
1
GND
2
EN
3
BYPASS
4
FB
5
VOUT
6
C6
102
R2
20K 1%
VCC33
C2
106/X5R
R1 33K1 %
C4
103
C1 22PF
C3
106/X5R
R3
68K
VCC33
P_GND
P_GND
P_VDD
P_GND P_GND
Figure 3.2.9.1 3.3V power circuit schematic diagam
Battery protection circuit equivalent circuit diagram is shown in he figure 3.2.8.2:
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