5/12

AN2031 APPLICATION NOTE

4.4 THD+Noise Ratio versus frequency at different output power Input power supply:

25V; Output load: 4

Ω;

Blue: 0dB; Cyan: -10dB; Green: -20dB;

Figure 4. Audio Precision

5 SCHEMATIC AND LAYOUT

5.1 Schematic

Figure 5. Power Section

0.01

1

0.02

0.05

0.1

0.2

0.5

%

20

20k

50

100

200

500

1k

2k

5k

10k

Hz

0.01

1

0.02

0.05

0.1

0.2

0.5

%

20

20k

50

100

200

500

1k

2k

5k

10k

Hz

2A5

C6

100n

5V

L5

FERRITE

D1

3A3

Vcc

L2

LCL

J1

+5V

2

1

GND

Logic

+

C3

330u 10V

R1

10K

L4

FERRITE

+

C8

10u 50V

C14

100n

+

C2

100u 10V

C7

100n

+

C4

10u 10V

JP3

2V5

+

C13

10u 10V

R3

9.1K

J2

+30V

1

2

Pwr

GND

JP2

2A5

C9

220n 50V

JP1

5V SEL

3

1

2

Int

Ext

Sel

U1

L4971D

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

C15

100n

C16

100n

Vicino all'STA308

2V5

C12

22n

U2

LD1086DT33

2

3

OUT

IN

C5

100n

U3

LD1086DT25

2

3

OUT

IN

C10

100n

C1

100n

R2

2.7K

L3

FERRITE

JP4

C11

2.2n

R4

4.7K

L6

FERRITE

L1 220u

3V3