Panasonic KX-MB772CX - Page 24

KX-MB262CX/KX-MB772CX
6.
17
.
Ma
in
Bo
ar
d S
ec
ti
on
3.3V
Power S
upply descrip
tions
•
IC 302 decreases the output voltage when N
PN transistor insta
lled chopper amplifier type switching regulator produce
s 2.3A min
or over at the output
voltage.
Oscillation frequency is set at
approximately 500kHz.
•
C375 and D302 are boost cir
cuits as a base dr
iving voltage for buit-in trans
istors.
•
D301,R31
1,R312,R313,C375,Q3
00,R318,Q301are UVLO (Under Volt
age Lock Out) circuit.
Q301 turns on when the in-out
voltage is 17V or less and
SS/SE terminal becomes low so that IC302's operation is stopped.
•
D303 controls no to be a ov
er voltage at 3.3V output w
hen ICs including IC302 bre
ak down.
1.2V Power Supply descriptions
•
IC305 is Nch FET used Switching Regulator with sy
nchronous rectification sy
stem.
Oscillation frequency is set at
approximately 350kHz.
•
R356 is a resistor f
or decreasing the output volt
age when the output current s
hows high.
The value is
compared with the voltage drop
at FET
.
•
C395 and D305 are FET's
boost circuit as a gate d
riving voltage.
2
0
1
0
2
6
6
6
7
3
0
1
E
1
1
4
9
0
9
2
1
1
0
0
6
4
6
8
2
9
1
D
1
1
5
9
0
9
2
2
9
7
6
1
6
9
2
8
1
C
1
1
6
9
0
9
2
3
9
5
5
F
7
0
2
7
1
B
1
1
7
8
0
8
2
4
9
3
5
D
7
1
2
7
1
B
1
1
8
8
0
8
2
5
9
1
5
B
7
2
2
6
1
A
1
1
9
8
0
8
2
6
8
8
5
8
7
3
2
5
1
9
1
2
0
8
0
8
Temperature
[C
°
]
AD value
HEX reading
T
emperature
[C
°
]
AD value
HEX reading
T
emperature
[C
°
]
AD value
HEX reading