Circuit Operation (Handset) - Panasonic KX-TCD410RUM Service Manual

22 CIRCUIT OPERATION (HANDSET)

22.1. Outline
Handset consists of the following ICs as shown in BLOCK DIAGRAM (HANDSET) (P.56).
· DECT BBIC (Base Band IC): IC1
− − All data signals (forming/analyzing ACK or CMD signal)
− − All interfaces (ex: Key, Detector Circuit, Charge, DC/DC Converter, EEPROM, LCD)
· RF Module: IC3
− − PLL Oscillator
− − Detector
− − Compress/Expander
− − Amplifier for transmission and reception
22.2. Power Supply Circuit/Reset Circuit
Circuit Operation:
When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6V: TP3) → TP14(4V) → IC3(6, 27), D3 → IC1(37) → IC1(39, 63) (2.65V)
The Reset signal generates R19, C23 and 2.65V.
22.3. Charge Circuit
Circuit Operation:
· When charging the handset on the Base Unit, the charge current is as follows;
DC+(5.5V ~ 6V) → D4 → R43, R44 → CHARGE+(Base) → CHARGE+(Handset) → L4 → Q2→ F1 → BATTERY+ ... Battery
... BATTERY- → R21 → GND → L5 → CHARGE-(Handset)→ CHARGE-(Base) → GND → DC-(GND)
· When charging the handset on the Charger Unit, the charge current is as follows;
DC+(5.5V ~ 6V) → D1 → R1, R2 → CHARGE+(Charger Unit) → CHARGE+(Handset)→ F1 → BATTERY+ ... Battery ...
BATTERY- → R21 → GND → CHARGE-(Handset)→ CHARGE-(Charger Unit) → 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 Q2 of Handset.
Refer to Fig.101 in Power Supply Circuit (P.54).
22.4. 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) < 2.3V
The BBIC detects this level and "
· Power Down
Battery voltage: V(Batt) < 2.2V
The BBIC detects this level and power down.
KX-TCD410RU M / KX-TCD410R US / KX-TCD412R UM / KX-TCD412R US / KX-A141RU M / KX-A141RU S / KX-A142RU M / KX-A142RUS
" starts flashing and "battery alarm" starts ringing.
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