Charge Circuit; Battery Low/Power Down Detector; Speakerphone - Panasonic KX-TG6841B Service Manual

KX-TG6841B/KX-TG6842B/KX-TG6843B/KX-TG6844B/KX-TG6845B/KX-TG6873B/KX-TGA680B
4.7.3.

Charge Circuit

Circuit Operation:
When charging the handset on the Base Unit, the charge current is as follows;
DCP(5.5V) → F301 → R371 → R372 → D362 → CHARGE+(Base) → CHARGE+(Handset) → R8 → Q3 → F1 → BATTERY+...
Battery...
BATTERY- → R45 → GND → CHARGE-(Handset)→ CHARGE-(Base) → GND → DC-(GND)
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.
Refer to Fig.101 in Power Supply Circuit/Reset Circuit (P.13).
CHG +
CHG -
GND
4.7.4.

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.
4.7.5.

Speakerphone

The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.
R8
Q4
R4
47K
R6
10K
Q9
GND
R7
100K
2.35 V ± 50 mV
" starts flashing.
2.1 V ± 50 mV
Q2
C27
R2
Q3
BATT +
BATTERY
2CELL
BATT -
R45
GND
22
CHG CTRL (32)
BBIC
IC1
CHG DET (34)