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4.2.
Circuit Operation (Handset)
4.2.1.
Outline
Handset consists of the following ICs as shown in Block Diagram (Handset) (P.6).
• DECT BBIC (Base Band IC): IC201
- All data signals (forming/analyzing ACK or CMD signal)
- All interfaces (ex: Key, Detector Circuit, Charge, DC/DC Converter, LCD)
Include EEPROM and Flash memory
EEPROM stores the temporary operating parameters (for RF, etc.)
• AMP: IC401
- Single OP_AMP for SP
• MIDI: IC301
- 16-Tone 32-Poly PCM Sound Generator
- Port (LED direct driver with PWM)
• RF Block
- IC601
PLL Oscillator
Detector
Compress/Expander
Amplifier for reception
- IC602
Amplifier for transmission
Power control
4.2.2.
Power Supply Circuit/Reset Circuit
Circuit Operation:
When power on the Handset, the voltage is as follows;
BATTERY(3.5V~4.2V: Battery+) → Q104 (1.8V)
The Reset signal generates IC201 (78) and 1.8V.
4.2.3.
Charge Circuit
Circuit Operation:
When charging the handset on the charger, the charge current is as follows;
DC+(9V~10V) → IC601(6) → IC601(2) → L601 → JT601(Charger) → JT101(Handset) → L101 → Q101→ D102 → BAT-
TERY+... Battery... BATTERY- → R115 → GND → L102→ JT102(Handset) → JT602(Charger) → R616, R617, R618, R619 →
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 Q101 of Handset.
4.2.4.
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.
4.2.5.
Speakerphone and Headset Jack
The hands-free loudspeaker at CN401(1) and CN401(2) is used to generate the ring alarm. IC401 is used to switch off the tele-
phone loudspeaker and is used to amplify the signal to drive the hands-free loudspeaker. They are selected using the SP_AMP
line from pin 70 of the BBIC. 2.5mm headset jack is also available.
→ Q105 (2.7V)
3.5V ± 50mV
" starts flashing.
3.3V ± 50mV
7
KX-TCA256X
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