Transitions Between Shutdown and Playing

OutputStage

PSU

VPP

GND

IN

IN

VPP

GND

PWM

TAS5086

OUT

OUT

S0269-01

TAS5086

www.ti.com ................................................................................................................................................... SLES131C – FEBRUARY 2005 – REVISED JUNE 2008

It also has individual channel dc-blocking filters that are enabled by default.

Individual channel de-emphasis filters for 32, 44.1, and 48 kHz are included and can be enabled and disabled.

There is also a two-channel downmix result that can be output on SDOUT (I2S format). This result also can be

sent to the left and right front channels (channels 1 and 2) and/or to the center and subwoofer (channels 5 and 6)

as well.

A mixer on the subwoofer channel supports bass management configuration 1.

PWM output characteristics

• Up to 8× oversampling

• 12× at f

S = 32 kHz, 8× at fS = 48 kHz, 4× at fS = 96 kHz, 2× at fS = 192 kHz

• Fourth-order noise shaping

• ≥105-dB dynamic range, 0–20 kHz (TAS5086 + TAS5186 system measured at speaker terminals)

• THD < 0.06% (measured at TAS5086 outputs)

• Adjustable maximum modulation limit of 93.8% to 99.2%

The TAS5086 outputs are switching all the time with the noise shaper active. Mute is acheived by inputting a

zero into the noise shaper, with the noise shaper running and the output still switching. By using this approach,

the transitions between off and operation is avoided. The only exception is shutdown of surround channels as

described in the Surround Register (0x19) section.

Futhermore, the TAS5086 is designed to drive a load in single-ended and bridge-tied-load configurations. The

principle in the SE and BTL configurations is shown in Figure 8 and Figure 9. In both situations, care must be

taken to ensure correct start-up sequences which charge the bootstrap capacitor and do not produce audible

artifacts; the TAS5086 is designed to do that.

Figure 8. BTL Filter Configuration

The SE configuration presents an additional challenge in order for starting up quietly. The second terminal of the

loudspeaker is connected to a split capacitor between power and ground. The advantage of this circuitly is that it

provides some degree of power-supply ripple rejection. The problem related to the split capacitor is that the

voltage over it must be controlled when the modulator starts (i.e., when the power stage output goes out of high

impedance state) to avoid a click in the speaker.

Copyright © 2005–2008, Texas Instruments Incorporated

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