Panasonic KX-FLC418RU, Service Manual

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54
KX-FLC418RU
6.16.2. Cordless Handset Circuit Operation
6.16.2.1. Outline
Cordless handset consists of the following ICs as shown in Cordless Handset Block Diagram (P.53).
• DECT BBIC ( B ase B and IC): IC1
- All data signals (forming/analyzing ACK or CMD signal)
- All interfaces (ex: Key, Detector Circuit, Charge, DC/DC Converter, EEPROM, LCD, RF Power Amp.)
- PLL Oscillator
- Detector
- Compress/Expander
- Reception
• RF Power Amp: IC801
- Amplifier for transmission
• EEPROM: IC3
- Temporary operating parameters (for RF, etc.)
6.16.2.2. Power Supply Circuit/Reset Circuit
Circuit Operation:
When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: BATT+)
→
F1
→
Q2 (1.8 V), IC1-43pin (2.5V)
The Reset signal generates IC1 (61 pin) and 1.8 V.
6.16.2.3. Charge Circuit
Circuit Operation:
When charging the cordless handset on the Base Unit, the charge current is as follows;
DC+(6.5 V)
→
D1
→
R56
→
R55
→
D22
→
(Base)
→
(Handset)
→
Q4
→
D7
→
F1
→
...
Battery...
BATTERY-
→
R45
→
GND
→
CHARGE-(Handset)
→
CHARGE-(Base)
→
GND
→
DC-(GND)
In this way, the BBIC on cordless handset detects the fact that the battery is charged.
The charge current is controlled by switching Q9 of cordless handset.
6.16.2.4. 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) 2.25V ± 50mV
The BBIC detects this level and " " starts flashing.
• Power Down
Battery voltage: V(Batt) 2.0V ± 50mV
The BBIC detects this level and power down.
6.16.2.5. Speakerphone
The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.