Panasonic KX-TCD287UAT / KX-TCA128UAT Service Manual ▷ View online
16 BLOCK DIAGRAM (HANDSET)
SPEAKER
RECEIVER
HEADSET
JACK
JACK
MIC
CHARGE
CIRCUIT
CIRCUIT
Q4,Q5,Q9
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
Q3
1.8V
Q2
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
80
80
72
62
52
45
44
58
56
59
60
6
9
10
77
ADPCM
Codec
Filter
DSP
Speech
Decoding
Speech
Encoding
BMC
Burst
ANT1
ANT2
Decoding
Burst
Encoding
RF
Interface
RF
Module
CN6
23
21
31
2
31
2
22
RXDA
TXDA
19
26
25
24
RSSI
SYDA
SYEN
SYCL
SYEN
SYCL
15
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
ANTENNA LIGHT
7
75
46
KX-TCA128 BLOCK DIAGRAM (HANDSET)
1
2
3
4
5
2
3
4
5
49
KX-TCD287UAT / KX-TCA128UAT
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, 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: BATTERY+)
→
F1, L1, D1
→
Q1 (4.0 V), Q2 (1.8 V), Q3 (3.3 V)
The Reset signal generates 1.8 V at pin53 of IC1.
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).
50
KX-TCD287UAT / KX-TCA128UAT
17.4. Battery Low/Power Down Detector
Circuit Operation:
“Battery Low” and “Power Down” are detected by BBIC (58 pin) 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)
2.05 ± 50mV
The BBIC detects this level and power down.
Refer to Check Point (Handset) (P.35)
17.5. Speakerphone
The hands-free loudspeaker at SP+ and SP- works as a ringer/alarm as well.
51
KX-TCD287UAT / KX-TCA128UAT
18 CIRCUIT OPERATION (CHARGER UNIT)
18.1. Power Supply Circuit
The power supply is as shown.
52
KX-TCD287UAT / KX-TCA128UAT
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