Kenwood 144MHz FM TRANSCEIVER K2E - Manual (Page 10)

TH-K2AT/K2E/K2ET
10
Power Supply Circuit
■ Charging Circuit
When an external power supply is connected to the DC IN
terminal, the constant-current circuit consisting of Q33 and
D31 provides a constant current of approx. 110 mA to the Ni-
MH battery.
If no external power supply is connected to the DC IN
terminal, the constant-current circuit does not function.
■ Power Supply Switching Circuit
The voltage supplied through the battery terminal or DC IN
terminal is branched in the power supply switching circuit as
shown in Fig.10 and then supplied to the required components.
■ Battery Type Recognition Circuit
When the battery pack is attached to the transceiver, the
battery type is recognized with the T terminal on the
transceiver. This battery type recognition activates charging
for the Ni-MH battery pack and displaying the battery meter.
+
-
T
B
J2
RN2701
XC6202PB
52FR
Q41
D32
D80
5T SW
Q37, Q38
2SK1830 5M
CHARGE
SW
RB051L-40
IC6
D48,49
D42,43,46
D47,44
BATT
CHARGE
5R SW
TK11250
CUCB
5.0V
TK11250
CM
AVR
5C SW
PROTECT
CPH3317
2SJ347
Q35
CHARGE
BTDET
Q34
Q57
D33
IC12
AVR
2SB1184
(Q,R)
2SC4617(R)
IC4
5MS SW
Q55
5MV SW
Q36
RB521S-30
DC-IN
DET
RN2105
AF AMP
2SB1184
(Q,R)
PROTECT
5.0V
11.5V
AF/LAMP
AVR
RN2105
Q53
PROTECT
THERM
DET
2SK1830
B
RB051L-40
Q33
AVR
IC9
B
PROTECT
D36
RB521S-30
D35
PROTECT
RB521S-30
PROTECT
D30
RB521S-30
IC8
MPU
D31
DA221
CONSTANT
CURRENT
BTEMP
DCDET
BATT TERMINAL
7.5V Norminal
(6.0 - 9.0V)
DC IN
13.8V Norminal
(12.0 - 16.0V)
IC1
TCXO
Q4,5,6
D40,41
5R
5T
VR1
ENC
5C
Q9,10,13
D8,10
TH1
IC16
Q47
5MV
IC3,17
D9,14
Q16,17
Q22,23,24
Q59
IC5
Q30
5MS
Fig. 10 Charging and Power supply switching circuit
Control System
■ Reset and Backup Circuit
When power is supplied to the transceiver, the 5M voltage
goes “H” as C303 is charged.
A rising edge of the 5M voltage is detected by the voltage
detection IC (IC11) and when its output (RESET) goes “H”,
the reset status of the MPU is released.
D35 R244
5M
5C
C307
R243
L63
BATT
5V
AVR
IC9
IC8
MPU
IC15
EEPROM
Timing chart
Power
ON
5V 5M
0
Power
OFF
IN OUT
C303
+
IC11
IN OUT
RESET
IC10
IN OUT INT
5V RESET
0
5V INT
0
If the supplied voltage to the transceiver is reduced and
the 5M voltage falls below the detection voltage of the voltage
detection IC (IC10), the MPU detects it by an interrupt
processing, backs up data in EEPROM (IC15) and turns the
power off.
Fig. 11 Reset and Backup circuit
CIRCUIT DESCRIPTION