SC7422

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

REV:1.0

2006.11.13

Http: www.silan.com.cn

Page 4 of 8

(Continued)

Pin No.

Pin Name

I/O

Pin Description

13

Bypass

O

Half supply voltage ripple rejection

14

-OUT1

O

Inverted loudspeaker output of channel 1

15

--

Supply

16

+OUT1

O

Non inverted loudspeaker output of channel 1

FUNCTION DESCRIPTION

Gain Setting for Input Stage

The gain for each audio input stage of the SC7422 is set by external resistors R1 and R2 (see typical

application circuit). It is recommended that R1 = R2 = 20k

Ω in the application and the gain is 0dB.

If the amplitude of audio input voltage is lower, for example, the peak-peak value is less than 2Vpp, it should be

improve the gain, whereas, it should be reduce the gain. However, the amplitude of audio input voltage is so high

that the output wave would be distortion. Therefore, the amplitude of audio signal source should be checked at

first. And the gain in the application should be set following Table 1.

Table 1 Gain Setting for Input Stage

Operation

Voltage

The peak-

peak value of

input voltage

Gain Setting

for Input

Stage

Operation

Voltage

The peak-

peak value of

input voltage

Gain Setting

for

Input Stage

+6dB

+6dB

0dB

0dB

-6dB

-6dB

Otherwise, the minimum value of input resistor R1 is 10k

Ω, in order to ensure proper impedance for input.

32 Steps Volume Control

The SC7422 includes a 32 steps volume controller. It changes the volume gain linearly with 1.5dB per step from

-45dB to 0dB. The volume is controlled by input voltage of DC Vol pin. As the voltage was increasing, the volume

Table 2 32 Steps Volume Setting

Step

Volume

(dB)

DC Vol

DC Vol

Step

Volume

(dB)

DC Vol

DC Vol

1

0

Vcc

64.2

17

-24

38.1

30.4

2

-1.5

64.4

62.8

18

-25.5

35.6

29.0

3

-3

63.0

61.2

19

-27

31.8

27.4

4

-4.5

61.4

59.4

20

-28.5

29.2

25.4

5

-6

59.8

57.6

21

-30

27.6

23.8

(To be continued)