TAS5558 datasheet(39/122 Pages) TI

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G003

Desired Gain − Linear

Digital Gain

Power-Supply Gain

0.00001

0.1

100

0.0001

0.01

100

0.001

0.1

0.0001

0.001

0.01

−60

−50

−40

−30

−20

−10

−80

−70

−60

−50

−40

−30

−20

−10

Desired Gain − dB

Digital Gain

Power-Supply Gain

G002

TAS5558

www.ti.com

SLES273A – APRIL 2013 – REVISED JUNE 2013

5.2.6

Power-Supply Volume Control (PSVC)

The TAS5558 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 I2C. 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)

TAS5558 Controls and Status

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