alc203-lf Realtek Semiconductor Corporation, alc203-lf Datasheet - Page 43

• Manufacturer Part Number: alc203-lf
• Description: Two-channel Ac?97 2.3 Audio Codec
• Manufacturer: Realtek Semiconductor Corporation

9.9 DC Voltage Volume Control
The ALC203 has a 32-step internal volume control that is controlled by the DC voltage applied to the ‘DC Vol’ pin (pin-33). The
volume control input range is from GND to AVDD. A low-speed counter ramp ADC transmits the DC voltage into a 5-bit
volume code to attenuate the master volume (real MX02), headphone volume (real MX04) and mono-out volume (real MX06).
A higher DC voltage means more attenuation related to output volume. The table below shows the relation between input DC
voltage and the 5-bit volume code.
92%< DC <= 95%
89%< DC <= 92%
86%< DC <= 89%
83%< DC <= 86%
80%< DC <= 83%
77%< DC <= 80%
74%< DC <= 77%
71%< DC <= 74%
68%< DC <= 71%
65%< DC <= 68%
62%< DC <= 65%
59%< DC <= 62%
56%< DC <= 59%
53%< DC <= 56%
50%< DC <= 53%
Input DC Voltage is ratio of AVDD (+5VA).
•This 5-bit volume code adds extra attenuation for master volume and headphone volume, the absolute maximum volume is
Two-Channel AC’97 2.3 Audio Codec
determined by MX02, MX04 and MX06.
Once the sum of MX value and volume code exceeds 3Fh, the real MX value is 3Fh.
Example 1: (Normal case)
Example 2: (The sum exceeds 3Fh for MX02/MX04, 1Fh for MX06)
Example 3: (Volume code is 1Fh, DCMute=1, real MXs should be muted)
95%=< DC
Input DC
Voltage
MX02=2F2Fh, MX04=2E2Eh, MX06=0002h, Volume Code=1Eh,
then Master Volume=3F3Fh, real Headphone Volume=3D3Dh, Mono-Out=001Fh
MX02=0000h, MX04=2020h, MX06=0010h, Volume Code=1Fh,
then Master Volume=9F1Fh, Headphone Volume=BF3Fh, Mono-Out=801Fh
MX02=0002h, MX04=0300h, MX06=0001h, Volume Code=2h,
then Master Volume=0204h, Headphone Volume=0502h, Mono-Out=0003h
Volume
Code
1D
1C
1B
1A
1F
1E
19
18
17
16
15
14
13
12
11
10
DCMute=1
DCMute=0
Note
47%< DC <= 50%
44%< DC <= 47%
41%< DC <= 44%
38%< DC <= 41%
35%< DC <= 38%
32%< DC <= 35%
29%< DC <= 32%
26%< DC <= 29%
23%< DC <= 26%
20%< DC <= 23%
17%< DC <= 20%
14%< DC <= 17%
11%< DC <= 14%
8%< DC <= 11%
5%< DC <= 8%
DC <= 5%
Input DC
Voltage
39
Volume
Code
D
A
E
C
B
F
9
8
7
6
5
4
3
2
1
0
DCMute=0
Note
ALC203 DataSheet
Rev1.6