Datasheet

LOUT /ROUT

filter

LOUT

filter

ROUT

TPA3121D2

www.ti.com

SLOS537A –MAY 2008–REVISED AUGUST 2010

Table 4. Recommended Filter Output Components

Output Configuration Speaker Impedance (Ω) Filter Inductor (mH) Filter Capacitor (nF)

4 22 680

Single Ended (SE)

8 33 220

Bridge Tied Load (BTL) 8 22 680

Figure 27. BTL Filter Configuration Figure 28. SE Filter Configuration

Power-Supply Decoupling, C

The TPA3121D2 is a high-performance CMOS audio amplifier that requires adequate power-supply decoupling

to ensure that 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 mF to 1 mF, placed as close as possible to the device V

lead works best. For

filtering lower frequency noise signals, a larger aluminum electrolytic capacitor of 470 mF or greater placed near

the audio power amplifier is recommended. The 470-mF capacitor also serves as local storage capacitor for

supplying current during large signal transients on the amplifier outputs. The PVCC terminals provide the power

to the output transistors, so a 470-mF or larger capacitor should be placed on each PVCC terminal. A 10-mF

capacitor on the AVCC terminal is adequate. These capacitors must be properly derated for voltage and

ripple-current rating to ensure reliability.

Power Supply Rejection

TPA3121D2 has good power supply rejection due to the closed-loop architecture; however, it is possible to

achieve better performance (if desired) by adding a filter between the PVCC supply and the AVCC supply. The

following figures illustrate the improvement that can be obtained by adding a 220Ω, 220mF filter before pins 19

and 20.

Product Folder Link(s): TPA3121D2