Panasonic KX-TG6451BX - Getting Started: Setup Guide; Connecting the Base Unit and Installing Batteries; Battery Charging Procedure

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KX-TG6451BX/KX-TGA641BX
1.4. Circuit Operation (Cordless Handset)
1.4.1. Outline
Cordless Handset consists of the following ICs as shown in Block Diagram (Cordless Handset) (P.6).
• 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 Power Amp.)
- PLL Oscillator
- Detector
- Compress/Expander
- Reception
• RF Power Amp: IC801
- Amplifier for transmission
• EEPROM: IC3
- Temporary operating parameters (for RF, etc.)
1.4.2. Power Supply Circuit/Reset Circuit
Circuit Operation:
When power on the Cordless 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.
1.4.3. Charge Circuit
Circuit Operation:
When charging the Cordless Handset on the Charger Unit, the charge current is as follows;
DC+(6.5 V) → F1 → R1 → CHARGE+(Charger) → CHARGE+(Cordless Handset) → L4 → Q4 → D7→ F1 → BATTERY+... Bat-
tery...
BATTERY- → L8 → R45 → GND → L5 → CHARGE-(Cordless Handset)→ CHARGE-(Charger) → 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.
1.4.4. 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) 2.25 V ± 50 mV
The BBIC detects this level and " " starts flashing.
• Power Down
Battery voltage: V(Batt) 2.0 V ± 50 mV
The BBIC detects this level and power down.
1.4.5. Speakerphone
The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.