Datasheet

0
–10
–20
–30
–40
–50
–60
–70
Magnitude – dB
0 0.2 0.4 0.6 0.8 1 1.2 1.4
FrequencyNormalizedtof
S
DACChannelResponseforInterpolationFilterC
(RedLineCorrespondsto –43dB)
TLV320AIC3120
SLAS653A –FEBRUARY 2010–REVISED MAY 2012 www.ti.com
5.6.1.4.3 Interpolation Filter C
Filter C is specifically designed for the 192-ksps mode. The pass band extends up to 0.4 × f
S
(corresponds to 80 kHz), more than sufficient for audio applications.
Table 5-26. Specification for DAC Interpolation Filter C
Parameter Condition Value (Typical) Unit
Filter-gain pass band 0…0.35 f
S
±0.03 dB
Filter-gain stop band 0.6 f
S
…1.4 f
S
–43 dB
Filter group delay 13/f
S
s
Figure 5-30. Frequency Response of DAC Interpolation Filter C
5.6.2 DAC Digital-Volume Control
The DAC has a digital-volume control block which implements programmable gain. Each channel has an
independent volume control that can be varied from 24 dB to –63.5 dB in 0.5-dB steps. The mono-channel
DAC volume can be controlled by writing to page 0 / register 65, bits D7–D0. DAC muting and setting up a
master gain control to control the mono channel is done by writing to page 0 / register 64, bits D3 and D1.
The gain is implemented with a soft-stepping algorithm, which only changes the actual volume by 0.125
dB per input sample, either up or down, until the desired volume is reached. The rate of soft-stepping can
be slowed to one step per two input samples by writing to page 0 / register 63, bits D1–D0. Note that the
default source for volume-control level settings is controlled by register writes to page 0 / register 65. Use
of the VOL/MICDET pin to control the DAC volume is ignored until the volume control source selected has
been changed to pin control (page 0 / register 116, bit D7 = 1). This functionality is shown in Figure 1-1.
During soft-stepping, the host does not receive a signal when the DAC has been completely muted. This
may be important if the host must mute the DAC before making a significant change, such as changing
sample rates. In order to help with this situation, the device provides a flag back to the host via a read-
only register, page 0 / register 38, bit D4 for the mono channel. This information alerts the host when the
part has completed the soft-stepping, and the actual volume has reached the desired volume level. The
soft-stepping feature can be disabled by writing to page 0 / register 63, bits D1–D0.
If soft-stepping is enabled, the CODEC_CLKIN signal should be kept active until the DAC power-up flag is
cleared. When this flag is cleared, the internal DAC soft-stepping process is complete, and
CODEC_CLKIN can be stopped if desired. (The analog volume control can be ramped down using an
internal oscillator.)
50 APPLICATION INFORMATION Copyright © 2010–2012, Texas Instruments Incorporated
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