12
3.2.9. Battery charge circuit
When the power is turn on, D12 and D13 turn on, thus +5V is applied to VBB line and
Recharge current is applied to the rechargeable battery via R31.
When the power is turned off, D12 and D13 turned off, thus battery output is applied to VBB.
When the power is turned off, battery output backs up the memory contents of RAM chip and
CPU internal RAM.
D13
3.2.10. PF circuit
When the power is off, the PF is “L”. But when the power is on, the Q27,Q33 are turn on the PF is
“H”.
+21.8V 24.4V
17.2V
PF
signal
+5V
C32
100u
C33
100u
S1B_S8
D12
S1B_S8
R31
150
BT1
BATTERY
+5V
VBB
PS_+5V
10V
10V
C53
4.7u
D20
HZU16B
2
3
1
Q33
DTC124EUA
2
1
3
Q27
DTA143ZUA
R33
1K
R32
1K
+24V
+5V
50V
PF