TAS5112

SLES048C − JULY 2003 − REVISED MARCH 2004

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13

Timing and Function

The function of the autorecovery circuit is as follows:

1.

An error event occurs and sets the

protection latch (output stage goes Hi-Z).

2.

The counter is started.

3.

After n/2 cycles, the protection latch is

cleared but the output stage remains Hi-Z

(identical to pulling RESET low).

4.

After

n cycles, operation is resumed

(identical to pulling RESET high) (n = 512).

Error

Protection

Latch

Shutdown

Autorecovery

SD

PWM

Counter

AR-RESET

Figure 10. Autorecovery Function

Latching Shutdown on All Errors (PMODE1)

In latching shutdown mode, all error situations result in a

power down (output stage Hi-Z). Re-enabling can be done

by toggling the RESET pin.

All Protection Systems Disabled (PMODE2)

In PMODE2, all protection systems are disabled. This

mode is purely intended for testing and characterization

purposes and thus not recommended for normal device

operation.

MODE Pins Selection

The protection mode is selected by shorting M1/M2 to

DREG or DGND according to Table 2.

Table 2. Protection Mode Selection

M1

M2

PROTECTION MODE

0

0

Autorecovery after errors (PMODE 0)

0

1

Latching shutdown on all errors (PMODE 1)

1

0

All protection systems disabled (PMODE 2)

1

1

Reserved

The output configuration mode is selected by shorting the

M3 pin to DREG or DGND according to Table 3.

Table 3. Output Mode Selection

M3

OUTPUT MODE

0

Bridge-tied load output stage (BTL)

1

Reserved

APPLICATION INFORMATION

DEMODULATION FILTER DESIGN

The PurePath Digital amplifier outputs are driven by

heavy-duty

DMOS

transistors

in

an

H-bridge

configuration. These transistors are either off or fully on,

which reduces the DMOS transistor on-state resistance,

R(DMOSon), and the power dissipated in the device,

thereby increasing efficiency.

The result is a square-wave output signal with a duty cycle

that is proportional to the amplitude of the audio signal. It

is recommended that a second-order LC filter be used to

recover the audio signal. For this application, EMI is

considered important; therefore, the selected filter is the

full-output type shown in Figure 11.

Output A

C1A

TAS51xx

L

Output B

L

C1B

C2

R(Load)

Figure 11. Demodulation Filter

The main purpose of the output filter is to attenuate the

high-frequency switching component of the PurePath

Digital amplifier while preserving the signals in the audio

band.

Design of the demodulation filter affects the performance

of the power amplifier significantly. As a result, to ensure

proper operation of the overcurrent (OC) protection circuit

and meet the device THD+N specifications, the selection

of the inductors used in the output filter must be considered

according to the following. The rule is that the inductance

should remain stable within the range of peak current seen

at maximum output power and deliver at least 5

µH of

inductance at 15 A.

If this rule is observed, the TAS5112 does not have

distortion issues due to the output inductors and

overcurrent conditions do not occur due to inductor

saturation in the output filter.