Charge Circuit; Battery Low/Power Down Detector - Panasonic KX-TCD540NZM Service Manual

23.3. Charge Circuit

Circuit Operation:
When charging the cordless handset on the Base Unit, the charge current is as
follows;
DC+(5.5V ~ 6V)
Handset) L4
GND CHARGE-(Cordless Handset)
In this way, the BBIC on Cordless Handset detects the fact that the battery is
charged.
The charge current is controlled by switching Q5 of Cordless Handset.
Refer to Fig.101 in
).

23.4. 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.
Refer to Adjustment (Cordless Handset)
).
23.5. Speakerphone and Headset Jack
D1 R4, R5 CHARGE+(Base)
Q4 D7 F1
Power Supply Circuit
2.3V ± 50mV
2.2V ± 50mV
BATTERY+ ... Battery ... BATTERY-
CHARGE-(Base)
(
" starts flashing.
(
120
CHARGE+(Cordless
GND DC-(GND)
R43