Datasheet

3−18
Microprocessor
2048 Sample
Transition
4096 Sample
Transition
Soft Volume
Gain Control
Soft Volume
volume_setting
VSC
Subaddress 0xF1
= 1
VSC
Subaddress 0xF1
= 0
I
2
C Slave Mode
I
2
C Master Mode
I
2
C
Volume
Commands
GPIO
Volume
Commands
f (Volume)
Programmable
Biquad Filter
Channel-Processed
Audio
Loudness Compensation
Volume-Adjusted
Audio
Figure 3−15. Soft Volume and Loudness Compensation Block Diagram
Figure 3−15 is a more detailed block diagram of soft volume and loudness compensation, and includes the I
2
C
subaddress commands that control volume and loudness compensation. Volume control is accomplished using three
I
2
C subaddresses—volume control, mute/unmute control, and volume slew rate control.
Volume control in the TAS3103 applies a linear gain. The volume commands issued via I
2
C subaddresses 0xF2,
0xF3, and 0xF4 (monaural channels 1, 2, and 3 respectively) are signed 5.23 format numbers. These commands are
applied to mixers, whose other input port is the audio data stream. The mixer output is the product of the audio data
stream and the volume command. Examples of volume command settings are given below.
Volume Command = 0x3580B07 = 0011_0.101_1000_0000_1011_0000_0111 = 6.6878365
Volume Command = 0x01F0000 = 0000_0.001_1111_0000_0000_0000_0000_0000 = 0.2421875
Volume Command = 0xCD6EFFE = 1100_1.101_0110_1110_1111_1111_1110 = −6.3208010
The volume control range is 0 = −∞ to 2
−23
= −138.47 dB to 2
4
− 2
−23
= 24.08 dB. Volume control is achieved by means
of a 5.23 format gain coefficient that is applied to a linear mixer. The volume gain setting realized, for a given volume
gain coefficient is:
Gain = 20log (Volume_Gain_Coefficient)