Datasheet

G003
Desired Gain − Linear
Power-Supply and Digital Gains − dB
Digital Gain
Power-Supply Gain
0.00001 0.1 100
0.0001
0.01
10
100
1
0.001
0.1
1
100.0001 0.001 0.01
−60
−50
−40
−30
−20
−10
0
10
20
30
−80 −70 −60 −50 −40 −30 −20 −10 0 10 20 30
Desired Gain − dB
Power-Supply and Digital Gains − dB
Digital Gain
Power-Supply Gain
G002
TAS5548
SLES270 –NOVEMBER 2012 www.ti.com
5.2.6 Power-Supply Volume Control (PSVC)
The TAS5548 supports volume control both by conventional digital gain/attenuation and by a combination
of digital and analog gain/attenuation. Varying the H-bridge power-supply voltage performs the analog
volume control function. The benefits of using power-supply volume control (PSVC) are reduced idle
channel noise, improved signal resolution at low volumes, increased dynamic range, and reduced radio
frequency emissions at reduced power levels. The PSVC is enabled via I
2
C. When enabled, the PSVC
provides a PWM output that is filtered to provide a reference voltage for the power supply. The power-
supply adjustment range can be set for –-12.04, –18.06, or –24.08 dB, to accommodate a range of
variable power-supply designs.
Figure 5-1 and Figure 5-2 show how power-supply and digital gains can be used together.
The volume biquad (0xCF) can be used to implement a low-pass filter in the digital volume control to
match the PSVC volume transfer function. Note that if the PVSC function is not used, the volume biquad
is all-pass (default).
Figure 5-1. Power-Supply and Digital Gains (Linear Space)
Figure 5-2. Power-Supply and Digital Gains (Log Space)
40 TAS5548 Controls and Status Copyright © 2012, Texas Instruments Incorporated
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