KX-PRW110UAW, KX-PRWA10RUW - Panasonic Telephone Service Manual (repair manual). Page 14

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Handset consists of the following ICs as shown in Block Diagram (Handset) (P.13).

• 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
- Integrated 1.9 GHz PA for DECT

• QSPI FLASH MEMORY: IC2

- Main Program D/L Area

• EEPROM: IC3

- Temporary operating parameters (for RF, etc.)

• SPI FLASH MEMORY: IC4

- Wall paper, Ringer Tone D/L Area.

When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: BATT+) 

→ P1 → L3 → Q8 → Q6 (1.8 V), Q7 (3.0V)

The Reset signal generates IC1 (B8 pin) and 1.8 V.

When charging the handset on the Base Unit, the charge current is as follows;

DC+(5.5 V) 

→ R371 → R372 → D362 → CHARGE+(Base) → CHARGE+(Handset) → 

 

→ Q2 → P1 → BATTERY+...

Battery... 
BATTERY- 

→ R1→ 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 Q4 of Handset.
Refer to Fig.101 in Power Supply Circuit (P.11).

“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.

1.8 V

Reset
(IC1_B8pin)

Battery +

Q3
R4