TAS5504 datasheet(37/96 Pages) TI

37 / 96 page

Introduction

SLES123 − October 2004

TAS5504

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THD < 0.01%

•

Adjustable maximum modulation limit of 93.8% to 99.2%

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3.3-V digital signal

1.12.1

DC Blocking (High Pass Enable/ Disable)

Each input channel incorporates a first order digital high-pass filter to block potential dc components. The filter

–3 dB point is approximately 0.89-Hz at 44.1-kHz sampling rate. The high-pass filter can be enabled and

disabled via the I2C interface.

1.12.2

De-Emphasis Filter

For audio sources that have been pre-emphasized, a precision 50 µs/15 µs de-emphasis filter is provided to

support the sampling rates of 32 kHz, 44.1 kHz, and 48 kHz. Figure 1−21 shows a graph of the de-emphasis

filtering characteristics. De-emphasis is set using two bits in the system control register.

−10

Frequency − kHz

3.18 (50 µs)

10.6 (15 µs)

Figure 1−21. De-emphasis Filter Characteristics

1.12.3

Power Supply Volume Control (PSVC)

The TAS5504 supports volume control by both 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 powers 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 power supply volume control (PSVC) is enabled via I2C. When enabled the

PSCV 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 1−22 and Figure 1−23 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.

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