Panasonic KX-MB2061CXB Service Manual page 87

6.22.2. Circuit Operation (Cordless Handset)
6.22.2.1. Outline
Cordless handset consists of the following ICs as shown in Block Diagram (P.86).
• 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.)
6.22.2.2. 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.
6.22.2.3. 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 → CHARGE+(Base) → CHARGE+(Handset) → Q4 → D7→ F1 → BATTERY+...
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.
6.22.2.4. 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)
The BBIC detects this level and "
• Power Down
Battery voltage: V(Batt)
The BBIC detects this level and power down.
6.22.2.5. Speakerphone
The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.
2.25V ± 50mV
" starts flashing.
2.0V ± 50mV
87
KX-MB2061CXB/KX-MB2061CX2/KX-MB2062CXB