Circuit Operation (Handset); Outline; Power Supply Circuit/Reset Circuit; Charge Circuit - Panasonic KX-TCA181RUT Service Manual

KX-TCD815RUS / KX-TCD815RUT / KX-TCA181RUS / KX-TCA181RUT

17 CIRCUIT OPERATION (HANDSET)

17.1. Outline

Handset consists of the following ICs as shown in BLOCK DIAGRAM (HANDSET) (P.49).
• • • • 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, USB_controller, IrDA, RF_module, Rom, Ram, LED,
LCD)
• • • • RF Module: IC20
− − − − PLL Oscillator
− − − − Detector
− − − − Compress/Expander
− − − − Amplifier for transmission and reception
• • • • AMP: IC2
− − − − Single OP_AMP for SP
• • • • USB controller
− − − − Data communication with a computer (ex. Personal computer) using the bi-directional serial interface
• • • • IrDA (Infra-red Data Association): IC21
− − − − Bi-directional communication using the infrared ray
• • • • FLASH MEMORY: IC11
− − − − Source program data and temporary user data are stored
• • • • RAM: IC13
− − − − Application data and code are temporary stored

17.2. Power Supply Circuit/Reset Circuit

Circuit Operation:
When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: BATTERY+) → F1, L1, D1 → Q2 (1.8 V), Q3 (3.3 V), Q1 (4.0 V)
The Reset signal generates IC1 (120 pin) and 1.8 V.

17.3. Charge Circuit

Circuit Operation:
When charging the handset on the Base Unit, the charge current is as follows;
DC+(5.5V ~ 6V) → D1 → R4, R5 → CHARGE+(Base) → CHARGE+(Handset) → L4 → Q4 → D7→ F1 → BATTERY+...
Battery... BATTERY- → R43 → GND → CHARGE-(Handset)→ CHARGE-(Base) → 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 Q5 of Handset.
Refer to Fig.101 in Power Supply Circuit (P.47).

17.4. 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.
2.25V ± 50mV
" starts flashing.
2.05 ± 50mV
50