參數(shù)資料
型號: TLV320AC57DW
廠商: Texas Instruments, Inc.
英文描述: 3-V VOICE-BAND AUDIO PROCESSORS VBAPE
中文描述: 3伏的語音頻帶音頻處理器VBAPE
文件頁數(shù): 23/46頁
文件大小: 452K
代理商: TLV320AC57DW
SLAS428 AUGUST 2004
www.ti.com
23
In a third programmable configuration, the ’DAC26 can be programmed to monitor and automatically power down the audio
output drivers upon detection of a short-circuit condition (Page2, REG1DH, bit D7), in addition to setting the short-circuit
flag in Page2, REG1DH, bitD6. When the device has detected a short and resulted in this condition, the short-circuit flag
is cleared when all the routings to the speaker driver are disabled (i.e., DAC, Analog Mixer, and Keyclick blocks are powered
down by user).
AUDIO OUTPUT DRIVER POWER-ON POP REDUCTION SCHEME
The ’DAC26 implements a pop reduction scheme to reduce audible artifacts during power up and power down of the audio
output drivers. This scheme can be controlled by programming bits D2 and D1 of REG1EH/Page2. By default, the driver
pop reduction scheme is enabled and can be disabled by programming bit D2 of Reg1EH/Page2 to
1
. When this scheme
is enabled and the virtual ground connection is not used (VGND amplifier is powered down), the audio output driver slowly
charges up any external ac-coupling capacitors to reduce audible artifacts. Bit D1 of REG1EH/Page2 provides control of
the charging time for the ac-coupling capacitor as either 0.8 sec or 4 sec. When the virtual ground amplifier is powered up
and used, the external ac-coupling capacitor is eliminated, and the power up time becomes 1 ms. This scheme takes effect
whenever the audio output drivers are powered up due to enabling any of the DAC, the Analog Mixer, or the Keyclick
Generator.
Pop Reduction for DAC Routing
Whenever the audio DAC is powered on or off, a slight change in the output dc offset voltage may occur and can be heard
as a weak pop in the output. In order to reduce this artifact, the ’DAC26 implements a DAC pop reduction scheme, which
is programmable using bits D5D2 in REG1DH/Page2. Bit D5 enables the scheme, which implements a slow transition
between the starting dc level and the final dc level. For best results, program bits D4D2 in REG1DH/Page2 to
100
.
AUDIO MIXING
Analog Mixer
The analog mixer can be used to route the analog input selected (MICIN or AUX) through an analog volume control and
then mix it with the audio DAC output. The analog mixer feature is available only if single-ended MICIN or AUX is selected
as the input. This feature is available even if the DAC is powered down. The analog volume control in this path has a gain
range from 12 dB to –34.5 dB in 0.5-dB steps plus mute and includes soft-stepping logic. The internal oscillator is used
for soft-stepping whenever the DAC is powered down.
KEYCLICK
A special circuit has been included for inserting a squarewave signal into the analog output signal path based on register
control. This functionality is intended for generating keyclick sounds for user feedback. Register 04H/Page2 contains bits
that control the amplitude, frequency, and duration of the square-wave signal. The frequency of the signal can be varied
from 62.5 Hz to 8 kHz and its duration can be programmed from 2 periods to 32 periods. Whenever this register is written,
the square-wave is generated and coupled into the audio output, going to both audio outputs. The keyclick enable bit D15
of control register 04H/Page2 is reset after the duration of keyclick is played out. This capability is available even when
the DAC is powered down.
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