MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER

MP7782 Rev. 1.2

www.MonolithicPower.com

5

8/3/2005

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2005 MPS. All Rights Reserved.

TM

TYPICAL APPLICATION CIRCUIT

MP7782

NC

FB2

FB1

AGND

NC

EN

FB2

FB1

AGND

EN

1

2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

PGND1

SW1

VDD1

BS1

NC

PGND2

SW2

VDD2

BS2

NC

AUDIO IN

EN

+

-

+

C6

1

µF

16V

C1

27pF

C14

27pF

C4

2.2nF

C10

1pF

C13

1pF

C9

1

µF

16V

C2

1000

µF

35V

C3

1

µF

25V

C5

1

µF

D2

6.2V

D4

6.2V

D3A

MBRS130LTR

D3B

OPTIONAL

D5A

MBRS130LTR

D5B

OPTIONAL

C11

1

µF

L1

15

µH

L2 = L1

15

µH

C7

0.22

µF

50V

C30

0.47

µF

50V

C12

0.22

µF

50V

D1

1N4148

D6

1N4148

C8

1

µF

25V

OFF ON

MP7782_F01

GND

C15

390pF

C16

390pF

APPLICATION INFORMATION

COMPONENT SELECTION

The MP7782 uses a minimum number of external

components to complete a fully bridged Class D

audio amplifier. The circuit in Figure 1 shows a

typical application. Use the following sections to

customize the amplifier for your particular

application.

Setting the Voltage Gain

The voltage gain sets the output voltage swing

for a given input voltage swing and is set by the

following equation:

3

1

V

R

R

A

=

1

R

8

R

=

3

R

4

R

=

The maximum output voltage swing is limited by

the power supply. The MP7782 is a bridged

amplifier

and

the

output

load

is

driven

differentially. Each side of the load is limited to a

maximum

peak-to-peak

voltage

swing

maximum output power of the MP7782 amplifier,

set the amplifier gain such that the maximum

peak-to-peak input signal results in at least the

maximum peak-to-peak output voltage swing.

Setting the Switching Frequency

The idle switching frequency (the switching

frequency with no audio input signal) is a

C4, C10 and C13 and resistors R1, R3, R4 and

R8. Lower switching frequencies result in more

inductor ripple, causing more quiescent output

voltage ripple, increasing the output noise.

Higher switching frequencies result in more

power loss. The optimum quiescent switching

frequency is approximately 400KHz to 600KHz.

C10 and C13 are typically 1pF to 2.2pF. C4 is

used to program the idle switching frequency.