TLV320AIC3254_09 Datasheet, PDF (77/168 Pages) Texas Instruments – Ultra Low Power Stereo Audio Codec With Embedded miniDSP

TLV320AIC3254
www.ti.com
Ultra Low Power Stereo Audio Codec With Embedded miniDSP
SLAS549A – SEPTEMBER 2008 – REVISED OCTOBER 2008
The recommended DRC Attack Rate value is 1.9531e-4 dB per 1/DAC_FS.
5.14.3.5 DRC Decay Rate
When the DRC detects a reduction in output signal swing beyond the programmed DRC Threshold, the
DRC enters a Decay state, where the applied gain in Digital Volume Control is gradually increased to
programmed values. To avoid audible artifacts, the gain is slowly increased with a rate equal to the Decay
Rate programmed through Page 0, Register 70, D(3:0). The Decay Rates can be programmed from
1.5625e-3dB per 1/DAC_FS to 4.7683e-7dB per 1/DAC_FS. If the Decay Rates are programmed too high,
then sudden gain changes can cause audible artifacts. However, if it is programmed too slow, then the
output may be perceived as too low for a long time after the peak signal has passed.
The recommended Value of DRC Attack Rate is 2.4414e-5 dB per 1/DAC_FS.
5.14.3.6 Example Setup for DRC
• PGA Gain = 12 dB
• Threshold = -24 dB
• Hysteresis = 3 dB
• Hold time = 0 ms
• Attack Rate = 1.9531e-4 dB per 1/DAC_FS
• Decay Rate = 2.4414e-5 dB per 1/DAC_FS
Script
#Go to Page 0
w 30 00 00
#DAC => 12 db gain left
w 30 41 18
#DAC => 12 db gain right
w 30 42 18
#DAC => DRC Enabled for both channels, Threshold = -24 db, Hysteresis = 3 dB
w 30 44 7F
#DRC Hold = 0 ms, Rate of Changes of Gain = 0.5 dB/Fs'
w 30 45 00
#Attack Rate = 1.9531e-4 dB/Frame , DRC Decay Rate =2.4414e-5 dB/Frame
w 30 46 B6
#Go to Page 46
w 30 00 2E
#DRC HPF
w 30 34 7F AB 00 00 80 55 00 00 7F 56 00 00
#DRC LPF
W 30 40 00 11 00 00 00 11 00 00 7F DE 00 00
5.15 DAC Special Functions
5.15.1 Beep Generation
A special function has also been included in the processing block PRB_P25 for generating a digital
sine-wave signal that is sent to the DAC. This is intended for generating key-click sounds for user
feedback. A default value for the sine-wave frequency, sine burst length, and signal magnitude is kept in
the Tone Generator Registers Page 0/Registers 71 through 79. The sine wave generator is very flexible,
and is completely register programmable via 9 registers of 8 bits each to provide many different sounds.
Two registers are used for programming the 16-bit, two's-complement, sine-wave coefficient (Page 0,
Registers 76 and 77). Two other registers program the 16-bit, two's-complement, cosine-wave coefficient
(Page 0, Registers 78 and 79). This coefficient resolution allows virtually any frequency of sine wave in the
audio band to be generated up to DAC_FS/2.
Three registers are used to control the length of the sine burst waveform which are located on Page 0,
Registers 73, 74, and 75. The resolution (bit) in the registers of the sine burst length is one sample time,
so this allows great control on the overall time of the sine burst waveform. This 24-bit length timer
supports 16,777,215 sample times. (For example if DAC_FS is set at 48kHz, and the registers combined
value equals 96000d (01770h), then the sine burst would last exactly two seconds.)
Submit Documentation Feedback
Application Information
77