Panasonic KX-TCD235RUS / KX-TCD235RUT / KX-TCA121RUS / KX-TCA121RUT Service Manual ▷ View online
15.2. Power Supply Circuit
The power is supplied to the DECT BBIC, RF Module, EEPROM and Charge Contact from AC Adaptor (+6V) as shown in
Fig.101. The power supply is as follows;
Fig.101. The power supply is as follows;
•
•
•
•
DECT BBIC (IC4):
CN1 (+6V)
→
D1
→
IC1
→
Q2
→
IC4 (3.0V)
CN1 (+6V)
→
D1
→
IC1
→
Q3
→
IC4 (1.8V)
•
•
•
•
RF Module (IC2):
CN1 (+6V)
→
D1
→
IC11
→
IC2 (2.5V)
•
•
•
•
EEPROM (IC3):
CN1 (+6V)
→
D1
→
IC1
→
Q2
→
IC3 (3.0V)
•
•
•
•
FLASH MEMORY (IC8):
CN1 (+6V)
→
D1
→
IC1
→
Q2
→
IC8 (3.0V)
•
•
•
•
SP AMP (IC7):
CN1 (+6V)
→
D1
→
IC1
→
IC7 (4.0V)
•
•
•
•
Charge Contact (TP15):
CN1 (+6V)
→
D1
→
R2, R4
→
TP15
<Fig.101>
45
KX-TCD235RUS / KX-TCD235R UT / KX-TCA121RUS / KX-TCA121RUT
15.3. Telephone Line Interface
<Function>
•
•
•
•
Bell signal detection
•
•
•
•
Clip signal detection
•
•
•
•
ON/OFF hook circuit
•
•
•
•
Audio circuits
•
•
•
•
DTMF tone signal circuits
Bell & Clip (: Calling Line Identification Presentation: Caller ID) signal detection:
In the standby mode, Q4 is open to cut the DC loop current and decrease the ring load.
When ring voltage appears at the L1T (A) and L1R (B) leads (when the telephone rings), the AC ring voltage is transferred as
follows;
follows;
•
•
•
•
A
→
C13
→
R17
→
R24
→
IC4 Pin 107 (CID INp)
•
•
•
•
B
→
C12
→
R16
→
R32
→
IC4 Pin 112 (CID INn)
ON/OFF hook circuit:
In the standby mode, Q4 is open, and connected as to cut the DC loop current and to cut the voice signal. The unit is
consequently in an on-hook condition.
consequently in an on-hook condition.
When press SP Key onto the base unit or press the TALK Key onto the handset, Q5 turns on and then Q4 turns on, thus
providing an off-hook condition (active DC current flow through the circuit) and the following signal flow is for the loop current.
providing an off-hook condition (active DC current flow through the circuit) and the following signal flow is for the loop current.
•
•
•
•
A
→
D3
→
Q4
→
Q8
→
R45
→
R46
→
D3
→
B [OFF HOOK]
15.4. Transmitter/Receiver
Base Unit and Handset mainly consist of RF Module and DECT BBIC.
Base Unit and Handset transmit/receive voice signal and data signal through the antenna on carrier frequency.
Signal Path:
*Refer to SIGNAL ROUTE (P.50).
15.4.1. Transmitter Block
The voice signal input from the TEL LINE interface goes to RF Module (IC2) through DECT BBIC (IC4) as shown in BLOCK
DIAGRAM (BASE UNIT) (P.43)
DIAGRAM (BASE UNIT) (P.43)
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.
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. Handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver Block.
antenna. Handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver Block.
15.4.2. Receiver Block
The signal of 19.2 MHz band (18.81792 MHz ~ 18.97344 MHz) which is input from antenna is input to IC2 as shown in BLOCK
DIAGRAM (BASE UNIT) (P.43).
DIAGRAM (BASE UNIT) (P.43).
In IC2, the signal of 19.2 MHz band is downconverted 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.
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.
15.5. Pulse Dialling
During pulse dialing the hookswitch (Q4,Q5) is used to generate the pulses using the HOOK control signal, which is set high
during pulses. To force the line impedance low during the “pause” intervals between dial pulses, the PULSE_DIAL signal turns
on Q12.
during pulses. To force the line impedance low during the “pause” intervals between dial pulses, the PULSE_DIAL signal turns
on Q12.
46
KX-TCD235RUS / KX-TCD235R UT / KX-TCA121RUS / KX-TCA121RUT
16 BLOCK DIAGRAM (HANDSET)
SPEAKER
RECEIVER
MIC
CHARGE
CIRCUIT
CIRCUIT
Q4,Q5,Q9
R7
R7
CHARGE
CONTACTS
CONTACTS
CHARGE(+)
CHARGE(-)
CHARGE
CHARGE DETECT
EEPROM
SCL
SDA
SWITCHED
SUPPLY
SUPPLY
Q1
Q1
BATTERY
TERMINAL
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
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
CN6
23
22
RXDA
TXDA
19
26
25
24
RSSI
SYDA
SYEN
SYCL
SYEN
SYCL
16
17
XTAL
X1
10.368
MHz
MHz
BATTERY
61
ON SWITCH
KEYPAD
ROWS
COLUMNS
1,12,40,76
27,28,34,35,36,74
BBIC
IC1
IC3
11
LCD-BACK LIGHT
KEY-BACK LIGHT
SP-PHONE LIGHT
7
75
46
KX-TCA121 BLOCK DIAGRAM (HANDSET)
47
KX-TCD235RUS / KX-TCD235R UT / KX-TCA121RUS / KX-TCA121RUT
17 CIRCUIT OPERATION (HANDSET)
17.1. Outline
Handset consists of the following ICs as shown in BLOCK DIAGRAM (HANDSET) (P.47).
•
•
•
•
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: CN6
−
−
−
−
PLL Oscillator
−
−
−
−
Detector
−
−
−
−
Compress/Expander
−
−
−
−
Amplifier for transmission and reception
•
•
•
•
EEPROM: IC3
−
−
−
−
Temporary operating parameters (for RF, etc.)
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: J1)
→
L1, D1
→
Q2 (1.8 V), Q3 (2.5 V), Q1 (4.0 V)
The Reset signal generates IC1 (53 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.45).
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)
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.
Refer to Check Point (Handset) (P.34).
17.5. Speakerphone
The hands-free loudspeaker at SP+ and SP- works as a ringer/alarm as well.
Refer to Troubleshooting for Speakerphone (Handset) (P.37).
48
KX-TCD235RUS / KX-TCD235R UT / KX-TCA121RUS / KX-TCA121RUT
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