KX-TDA6381X, KX-TDA6381SX - Panasonic PBX Service Manual (repair manual). Page 17

17

The circuit which generates output +3.3V, +5V with input +15V. It is configured with the circuit that reduces the voltage from
+15V to +3.3V by IC801, Q801, D801 and L801 switching power supply, and with the circuit that reduces the voltage from +15V
to +5V by IC802, Q802, D802 and L802 switching power supply.
There are two protection lines. One is F1 for +15V short protection, the other is   the over voltage protection which detects

+3.3V/+5V voltage rise and make FET Q15 OFF.

PG

P.G

PG

P.G

PG

P.G

PG

P.G

PG

P.G

+3.3V

PG

P.G

PG

P.G

D

806

C

807

D803

C805

C

820

L802

C8

1

6

C

808

R

820

Q

801

S

D

G

L801

R817

R826

R8

1

3

Q1

6

1

6

2

L803

0

L8

1

1

C

818

C

821

D

802

D807

L8

1

0

R

812

R822

R816

D804

R8

0

2

R815

IC801

1

CE/CSS

2

VSS

3

FB

4 EXT/

5

VIN

Q1

6

4

3

5

R814

D8

0

1

IC802

1

CE/CSS

2

VSS

3

FB

4 EXT/

5

VIN

C

809

R827

D808

C8

1

7

L804

DA801

1

2

3

Q8

0

2

S

D

G

C

810

C8

1

9

C815

R

819

R

801

C806

Q1

5

S

D

G

R8

1

1

R821

R8

2

5

R8

2

4

+15VIN

+3.3V

+5V

PG

P.G

IP1

CN1

A1

+15VPTA1

B1

+15VPTB1

A2

+40V

B2

+15V

A3

POWER_GNDA3

B3

POWER_GNDB3

+15V

+15V

C

801

R810

TH1

+15VIN