Cordless Handset consists of the following ICs as shown in BLOCK DIAGRAM (CORDLESS
HANDSET) ().
- 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
- AMP: IC2
- Single OP_AMP for SP
- MIDI (Musical Instrument Digital Interface): IC4
- 16-Tone 32-Poly PCM Sound Generator
- Port (LED direct driver with PWM)
- EEPROM: IC10
- Temporary operating parameters (for RF, etc.)
Refer to EEPROM LAYOUT (CORDLESS HANDSET) ().
22.2. Power Supply Circuit/Reset Circuit
Circuit Operation:
When power on the Cordless Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6V: J1) L1, D1, Q2 (1.8V) Q3 (2.7V) Q1 (4.0V)
The Reset signal generates IC1 (78) and 1.8V.
22.3. Charge Circuit
Circuit Operation:
When charging the cordless handset on the Base Unit, the charge current is as follows;
DC+(5.5V ~ 6V) D1 R4, R5 CHARGE+(Base) CHARGE+(Cordless Handset) L4
Q4 D7 F1 BATTERY+ ... Battery ... BATTERY- R43 GND CHARGE-(Cordless
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 Q5 of Cordless Handset.
Refer to Fig.101 in Power Supply Circuit ().
22.4. Battery Low/Power Down Detector
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