TPA005D02

2-W STEREO CLASS-D AUDIO POWER AMPLIFIER

SLOS227C – AUGUST 1998 – REVISED MARCH 2000

13

POST OFFICE BOX 655303

APPLICATION INFORMATION

mute and shutdown modes

The TPA005D02 employs both a mute and a shutdown mode of operation designed to reduce supply current,

input terminal should be held high during normal operation when the amplifier is in use. Pulling SHUTDOWN

Table 2. Shutdown and Mute Mode Functions

INPUTS†

OUTPUT

AMPLIFIER STATE

SE/BTL

HP/LINE

MUTE IN

SHUTDOWN

MUTE OUT

INPUT

OUTPUT

Low

Low

Low

Low

Low

L/R Line

BTL

X

X

—

High

—

X

Mute

X

X

High

—

High

X

Mute

Low

High

Low

Low

Low

L/R HP

BTL

High

Low

Low

Low

Low

L/R Line

SE

High

High

Low

Low

Low

L/R HP

SE

† Inputs should never be left unconnected.

X = do not care

using low-ESR capacitors

Low-ESR capacitors are recommended throughout this applications section. A real (as opposed to ideal)

capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this

resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this

resistance the more the real capacitor behaves like an ideal capacitor.

output filter components

The output inductors are key elements in the performance of the class D audio amplifier system. It is important

that these inductors have a high enough current rating and a relatively constant inductance over frequency and

temperature. The current rating should be higher than the expected maximum current to avoid magnetically

saturating the inductor. When saturation occurs, the inductor loses its functionality and looks like a short circuit

to the PWM signal, which increases the harmonic distortion considerably.

A shielded inductor may be required if the class D amplifier is placed in an EMI sensitive system; however, the

switching frequency is low for EMI considerations and should not be an issue in most systems. The DC series

resistance of the inductor should be low to minimize losses due to power dissipation in the inductor, which

reduces the efficiency of the circuit.

Capacitors are important in attenuating the switching frequency and high frequency noise, and in supplying

some of the current to the load. It is best to use capacitors with low equivalent-series-resistance (ESR). A low

ESR means that less power is dissipated in the capacitor as it shunts the high-frequency signals. Placing these

capacitors in parallel also parallels their ESR, effectively reducing the overall ESR value. The voltage rating is

also important, and, as a rule of thumb, should be 2 to 3 times the maximum rms voltage expected to allow for

high peak voltages and transient spikes. These output filter capacitors should be stable over temperature since

large currents flow through them.