Panasonic KX-TG3711BXB Service Manual page 21

4.8.3. Charge Circuit
Circuit Operation:
When charging the handset on the Base Unit, the charge current is as follows;
DCP+(5.5 V) → F301 → R371 → R372 → D362 → CHARGE+(Base) → CHARGE+(Handset) →
BATTERY+... Battery...
BATTERY- → R45 → GND → CHARGE-(Handset)→ CHARGE-(Base) → GND → DCM
In this way, the BBIC on Handset detects the fact that the battery is charged.
The charge current is controlled by switching Q9 of Handset.
CHG +
CHG -
GND
4.8.4. Battery Low/Power Down Detector
Circuit Operation:
"Battery Low" and "Power Down" are detected by BBIC which check the voltage from battery.
The detected voltage is as follows;
• Battery Low
Battery voltage: V(Batt)
The BBIC detects this level and "
• Power Down
Battery voltage: V(Batt)
The BBIC detects this level and power down.
R4
R31
10K
Q9
GND
R5
1.2K
2.25 V ± 50 mV
" starts flashing.
2.0 V ± 50 mV
Q5
C19
R9
Q4
BATT +
Q6
BATTERY
BATT +
GND
R3
21
KX-TG3711BX/KX-TG3712BX/KX-TG3719BX/KX-TGA371BX
Q5
R4
2CELL
CHARGE CTRL (32)
CHARGE (33)
→ Q4 → F1 →
BBIC
IC1