TCD6000 Datasheet, PDF (23/36 Pages) Tripath Technology Inc. – 6 CHANNEL CLASS-T DIGITAL AUDIO PROCESSOR USING DIGITAL POWER PROCESSINGTM TECHNOLOGY

Tripath Technology, Inc. – Preliminary Technical Information
Volume Change Control
Addr
2Eh
Register Name
Volume Change Control
Default
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
VR1 VR0 VRE ZCE
0
0
0
0
0
1
0
0
This register is used to specify 3 characteristics of volume change for all channels:
- Coarse Gain (control bits VR0 and VR1)
- Volume Ramp Enable (control bit VRE)
- Zero-Crossing Enable (control bit ZCE)
Coarse Gain is a simple volume adjustment made by shifting bits to the left. Coarse Gain is set by selecting
one of four combinations for bits VR0 and VR1. Coarse Gain affects all 6 channels globally.
Coarse Gain can cause premature digital clipping when used with PGC because internal digital gain
approaches maximum at each PGC boundary. Therefore when using PGC, Coarse Gain should not be
enabled until maximum volume has been reached on all channels.
Bits VR1 VR0
0
0
1X volume
0
1
2X volume
1
0
4X volume
1
1
8X volume
The VRE control bit is the Volume Ramp Enable bit. If VRE = ‘1’, the contents of the Volume Ramp Rate
Register will be read and determine how fast the volume can ramp up or down on all 6 channels. Refer to
the Volume Ramp Rate Register section for a more detailed explanation of how the ramp rate is calculated.
The ZCE control bit is the Zero-Crossing Enable bit. A polarity inversion on the audio input signal is called a
“Zero-Crossing”. Changing volume only at Zero-Crossings helps to avoid popping sounds. If ZCE is set to
‘1’, volume will only be allowed to change at Zero-Crossings. However, if a Zero-Crossing does not occur
within a time defined by the Volume Ramp Rate Register (called “time-out” in the graph below), volume will
change anyway. If the Zero-Crossing feature is enabled, the VRE control bit will still control whether the
volume change occurs in one large step or in 1/8 dB steps at Zero-Crossings.
Amplitude
Volume change occurs at every
zero-crossing
Audio signal
No zero-crossing, volume change
occurs after time-out
time-out
Time
23
TCD6000 – Rev. 1.0/09.04