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13

Pin 6 of BBIC turns Q141 ON/OFF to make the pulse dialing.

Basically this circuit prevents the TX signal from feeding back to RX signal. As for this unit, TX signal feed back from Q161 is
canceled by the canceller circuit of BBIC.

The power supply voltage from AC adaptor is converted to VBAT (3.0V) in 3.0V DC/DC Converter (IC301,Q301) and +3.0V for
peripherals and analog part is insulated from VBAT by Doubler of BBIC.
Circuit Operation:

6.5V

VB AT

RSTN(Reset) 

pin 54

VB AT

pin 10

pin 57

pin 9

pin 15

IC501

IC301,Q301

IC601

BBIC

DOUBLER OUT
F or pe ripherals

VDDC (1.2V)

AC Adaptor

        3.0V
DC/DC
CONVERTER

FLASH

IC611

EEP R OM

+3.0V

STM/CKM

Recei ve

Amp.

RF P art

Sta rtmonitor

(IC501 57pin)

VDDC (1.2  V)

VB AT

Reset (RSTN) 
(IC501_54 pin)

BBIC chip initiali ze

(CKM/STM)

14

The voltage from the AC adaptor is supplied to the charge circuits.

The caller ID is a chargeable ID which the user of a telephone circuit obtains by entering a contract with the telephone company
to utilize a caller ID service. For this reason, the operation of this circuit assumes that a caller ID service contract has been
entered for the circuit being used. 
The Caller-ID data from exchange is supplied to the telephone using either method of FSK or DTMF. The method is chosen
according to the exchange of telephone office. This unit is available to receive the data with both methods and displays the
received data on LCD.

• FSK (Frequency Shift Keying) format

• DTMF  format

It is the method to send the telephone number of calling party with DTMF to the telephone. DTMF is sent before the first bell sig-
nal.
The data is sent in turn; first the start code, secondly the telephone number of calling party, lastly end code.
The DTMF is chosen from A (1633 Hz and 697 Hz), B (1633 Hz and 770 Hz), C (1633 Hz and 852 Hz) and D (1633 Hz and 941
Hz) as the start code and end code according to the exchange.

D362

R37

2

R371

CHARGE+

F301

DCP

CHARGE-

+6.5V

DCM

STD Ring / 20Hz
Tip-Ring

FSK

DATA in

1st Ring

Silent interval

2nd Ring

DATA

0.1Vrms

70Vrms

1300Hz or
1200Hz
=DATA "1"

2100Hz or
2200Hz
=DATA "0"

Startcode

Endcode

Calling party's 
telephone number

DTMF

1st Ring

0.1Vrms

70Vrms

15

SPEAKER

RECEIVER

MIC

CHARGE

CIRCUIT

Q4, Q6

Q9, R8Q

9

, 

R

8

CHARGE(+)

CHARGE_CTRL

CHARGE_DET

EEPR

O

M

SCL

SD

A

R45

VBA

T

BA

TT

-

1.8 V

Q2

1.8 V

CP 3.0 

V

LCD

CD

RESET

CSB

SD

A

 SCL

CPU

Analog

F

ront

End

D/A

A/D

37

35

25

24

21

20

34

33

63

64

 42

27

48

49

69

60

61

72

ADPCM

Codec

Filter

DSP

Speech

Decoding

Speech

Encoding

BMC

Burst

Decoding

ANT1

Burst

Encoding

RF 

PLL

MOD/DEMOD

2

3

87

86

RXn

ANT1

RXp

TXp

TXn

9

10

XT

AL

X1

10.368

MHz

BA

TTER

Y

50

ON SWITCH

KEYP

AD

Charge

Pump

RO

W

S

COLUMNS

CP3V

CP3.0V

CP_LED

54, 55, 56, 57

14, 15, 16, 17, 52

BBIC

 62

LDO_CTRL

CP3V

71

CHARGE

CONT

A

CTS

BA

TTER

Y

TERMINAL

KX-TGA250 BLOCK DIA

G

RAM (Handset)

BA

TTER

Y_ON

16

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

• DECT BBIC (Base Band IC): IC5

- 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

• 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: BATT+) → F1 → Q2 (1.8 V), IC5-48pin (3.0V)
The Reset signal generates IC5 (67 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) → Q4 → F1 → 
BATTERY + Battery...

BATTERY- → R45 → 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 Q9 of Handset.
Refer to Fig.101 in Power Supply Circuit

“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.

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

1.8 V

Reset
(IC5_67pin)

Battery +