TAS5508C
SLES257–SEPTEMBER 2010
www.ti.com
The PWM section also contains the power-supply volume control (PSVC) PWM.
The interpolator, noise shaper, and PWM sections provide a PWM output with the following features:
•
Up to 8× oversampling
–
–
–
8× at FS = 44.1 kHz, 48 kHz, 32 kHz, 38 kHz
4× at FS = 88.2 kHz, 96 kHz
2× at FS = 176.4 kHz, 192 kHz
•
•
•
•
•
Fifth-order noise shaping
100-dB dynamic range 0–20 kHz (TAS5508C + TAS5111 system measured at speaker terminals)
THD < 0.01%
Adjustable maximum modulation limit of 93.8% to 99.2%
3.3-V digital signal
2.12.1 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 the 44.1-kHz sampling rate. The high-pass filter can be
enabled and disabled via the I2C interface.
2.12.2 De-Emphasis Filter
For audio sources that have been pre-emphasized, a precision 50-ms/15-ms de-emphasis filter is provided
to support the sampling rates of 32 kHz, 44.1 kHz, and 48 kHz. Figure 2-19 shows a graph of the
de-emphasis filtering characteristics. De-emphasis is set using two bits in the system control register.
0
De-emphasis
−10
3.18 (50 µs)
10.6 (15 µs)
f – Frequency – kHz
M0015-01
Figure 2-19. De-Emphasis Filter Characteristics
2.12.3 Power-Supply Volume Control (PSVC)
The TAS5508C 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 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 2-20 and Figure 2-21 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.
40
Description
Copyright © 2010, Texas Instruments Incorporated
Submit Documentation Feedback
Product Folder Link(s): TAS5508C
TI [ TEXAS INSTRUMENTS ]
