TPA2000D2 datasheet(13/17 Pages) TI

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TPA2000D2

2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER

SLOS291B – MARCH 2000 – REVISED APRIL 2000

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

The value of CI is important as it directly affects the bass (low frequency) performance of the circuit. Consider

the example where ZI is 20 kΩ and the specification calls for a flat bass response down to 80 Hz. Equation 5

is reconfigured as equation 6.

I +

I fc

(6)

In this example, CI is 0.1 µF so one would likely choose a value in the range of 0.1 µF to 1 µF. If the gain is known

and will be constant, use ZI from Table 1 to calculate CI. A further consideration for this capacitor is the leakage

path from the input source through the input network (CI) and the feedback network to the load. This leakage

current creates a dc offset voltage at the input to the amplifier that reduces useful headroom, especially in high

gain applications. For this reason a low-leakage tantalum or ceramic capacitor is the best choice. When

polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most

applications as the dc level there is held at VDD/2, which is likely higher than the source dc level. Note that it

is important to confirm the capacitor polarity in the application.

CI must be 10 times smaller than the bypass capacitor to reduce clicking and popping noise from power on/off

and entering and leaving shutdown. After sizing CI for a given cut-off frequency, size the bypass capacitor to

10 times that of the input capacitor.

(7)

CI ≤ CBYP / 10

power supply decoupling, CS

The TPA2000D2 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling

to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also

prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is

achieved by using two capacitors of different types that target different types of noise on the power supply leads.

For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance

(ESR) ceramic capacitor, typically 0.1

µF placed as close as possible to the device VDD lead works best. For

filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10

µF or greater placed near

the audio power amplifier is recommended.

midrail bypass capacitor, CBYP

The midrail bypass capacitor, CBYP, is the most critical capacitor and serves several important functions. During

start-up or recovery from shutdown mode, CBYP determines the rate at which the amplifier starts up. The second

function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This

noise is from the midrail generation circuit internal to the amplifier, which appears as degraded PSRR and

THD+N.

Bypass capacitor, CBYP, values of 0.47 µF to 1 µF ceramic or tantalum low-ESR capacitors are recommended

for the best THD and noise performance.

Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving

shutdown. To have minimal pop, CBYP should be 10 times larger than CI.

(8)

CBYP ≥ 10 × CI

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