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The Gate Array (IC101) works only for writing the ASCII code from the data bus (D4~D7). V0 is supplied for the crystal drive. 
R123 and R124 are density control resistors. 
Consequently, in this unit, the timing (positive clock) is generated by the LCD interface circuitry in the gate array (IC101).

54

Base Unit and Cordless Handset mainly consist of RF Module and DECT BBIC. 
Base Unit and Cordless Handset transmit/receive voice signal and data signal through the antenna on carrier frequency.

The voice signal input from the TEL LINE interface goes to RF Module (IC2) through DECT BBIC (IC4).
The voice signal passes through the analog part of IC4 where it is amplified and converted to a digital audio stream signal. The
burst switch controller processes this stream performing encryption and scrambling, adding the various other fields to produce
the GAP (Generic Access Profile) standard DECT frame, assigning to a time slot and channel etc.
In IC2, the carrier frequency is changing, and frequency modulated RF signal is generated and amplified, and radiated from
antenna. Cordless Handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver
Block.

The signal of 1900 MHz band (1881.792 MHz ~ 1897.344 MHz) which is input from antenna is input to IC2.
In IC2, the signal of 1900 MHz band is down converted to 864 kHz signal and demodulated, and goes to IC4 as GAP (Generic 
Access Profile) standard DECT frames. It passes through the decoding section burst switch controller where it separates out the 
frame information and performs de-encryption and de-scrambling as required. It then goes to the DSP section where it is turned 
back into analog audio. This is amplified by the analog front end, and goes to the TEL LINE Interface.

The power is supplied to the DECT BBIC, RF Module, EEPROM and FLASH MEMORY as shown below figure.
The power supply is as follows;

• DECT BBIC (IC4):

CN921 8, 9 pin (+4V) 

→ Q8 → IC4

CN921 8, 9 pin (+4V) 

→ Q6 → IC4

• RF  Module  (IC2):

CN921 8, 9 pin (+4V) 

→ IC28 → IC2 (PLL)

CN921 8, 9 pin (+4V) 

→ IC28 → R411, R412 → IC2 (Power AMP)

• EEPROM (IC22):

CN921 8, 9 pin (+4V) 

→ Q8 → IC22

• FLASH MEMORY (IC23):

CN921 8, 9 pin (+4V) 

→ Q8 → IC23

55

KX-FLC413UA : CORDLESS HANDSET BLOCK DIAGRAM

SPEAKER

RECEIVER

MIC

CHARGE
CIRCUIT

Q4,Q5,Q9
R7

CHARGE
CONTACTS

CHARGE(+)

CHARGE(-)

CHARGE

CHARGE DETECT

EEPROM

SCL

SDA

SWITCHED
SUPPLY

    Q1

Q1

BATTERY
TERMINAL

D7

VBAT1

DC/DC-SWITCH

J1

J2

2.5V

Q3

1.8V

Q2

4.0V

2.5V

1.8V

LCD

RS

RESET

CS

SI

 SCL

CPU

Analog

Front

End

D/A

A/D

30

32

66

67
72

62

52

45

44

 58

56

  59 

 60

6

  9

10

77

ADPCM

Codec

Filter

DSP

Speech

Decoding

Speech

Encoding

BMC

Burst

Decoding

Burst

Encoding

RF

Interface

RF

Module

23

22

RXDA

TXDA

19

26

25

24

RSSI

SYDA
SYEN
SYCL

16

17

XTAL

X1

10.368
MHz

BATTERY

61

ON SWITCH

KEYPAD

ROWS

COLUMNS

1,12,40,76

27,28,34,35,36,74

BBIC

 11

LCD-BACK  LIGHT

KEY-BACK  LIGHT

Ringer LED

 7

75

46

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Handset consists of the following ICs as shown in Cordless Handset Block Diagram (P.55).

• 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: IC4

- PLL Oscillator
- Detector
- Compress/Expander
- Amplifier for transmission and reception

• EEPROM: IC3

- Temporary operating parameters (for RF, etc.)

When power on the Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: J1) 

→ F1, L1, D1 → Q2 (1.8 V), Q3 (2.5 V), Q1 (3.3 V)

The Reset signal generates IC1 (66 pin) and 1.8 V.

When charging the handset on the Base Unit, the charge current is as follows;
DC+(6.5V) 

→ R1, R2, R3, R4 → CHARGE+(Charger) → CHARGE+(Handset) → L4 → Q4 → D7 → F1 → BATTERY+...Bat-

tery...Battery- 

→ R45 → GND → L5 → CHARGE-(Handset)→ CHARGE-(Charger) → 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.

"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)   2.25V ± 50mV
The BBIC detects this level and "

" starts flashing.

• Power Down

Battery voltage: V(Batt)   2.0V ± 50mV
The BBIC detects this level and power down.

The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.

The power supply is as shown.