Introduction
30
SLES115 — August 2004
TAS5518
The interpolator, noise shaper, and PWM sections provide a PWM output with the following features:
Up to 8x over sampling.
8x at FS = 44.1 kHz, 48 kHz, 32 kHz, 38 kHz
4x at FS = 88.2 kHz, 96 kHz
2x at FS = 176.4 kHz, 192 kHz
5th order noise shaping
110-dB dynamic range 0 – 20 kHz (TAS5518 + TAS5182 system measured at speaker terminals)
THD < 0.01%
Adjustable maximum modulation limit of 93.8% to 99.2%
3.3-V digital signal
1.13.1
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.
1.13.2
De-Emphasis Filter
For audio sources that have been pre-emphasized, a precision 50 s/15 s de-emphasis filter is provided to
support the sampling rates of 32 kHz, 44.1 kHz, and 48 kHz.
Figure 122 shows a graph of the de-emphasis
filtering characteristics. De-emphasis is set using two bits in the system control register.
Response
dB
10
0
Frequency kHz
3.18 (50 s)
10.6 (15 s)
Figure 122. De-emphasis Filter Characteristics
1.13.3
Power Supply Volume Control (PSVC)
The TAS5518 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.
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.