IN-

IN+

PVDD

AGND

Oscillator

Adaptive

Boost

Converter

VBAT

Monitor

+

–

PWM

H-

Bridge

BGND

Bias

Control

EN

AGC

PGND

OUT-

OUT+

PVDD

SW

VBAT

AGC

TPA2025D1

www.ti.com

SLOS717B – AUGUST 2011 – REVISED DECEMBER 2014

9 Parameter Measurement Information

All parameters are measured according to the conditions described in the Specifications section.

Many audio analyzers will not give the correct readings on a Class-D amplifier without additional filtering, even if

they have an internal low-pass filter. A RC 30kHz low-pass filter (100-

Ω, 47n-F) is implemented to reduce the

remaining noise frequencies from the PWM carrier signal. This filter was used on each output for the data sheet

graphs.

10 Detailed Description

10.1 Overview

The TPA2025D1 is a constant output, high efficiency Class-D audio amplifier with battery tracking AGC

technology and an integrated Class-G boost converter. This features give the device a great performance and

enhances efficiency at low output power. The TPA2025D1 can drive up to 1.9 W into an 8-

Ω speaker (1%

THD+N).

The built-in boost converter operates from a battery supply voltage and generates a higher output voltage PVDD

at 5.75 V that drives the supply voltage of the Class-D amplifier. This provides a louder audio output than a

stand-alone amplifier directly connected to the battery.

The battery tracking AGC adjusts the Class-D gain to limit battery current at lower battery voltage. This lets the

device to extend the battery life while playing audio, typically with 85% efficiency. When the battery voltage is

below a certain threshold voltage, The TPA2025D1 lowers the audio loudness. The threshold is selectable with

an external pin.

The TPA2025D1 has an integrated low-pass filter to improve the RF rejection and reduce DAC out-of-band

noise, increasing the signal-to-noise ratio (SNR). The features included in this device allow it to be used in a wide

range of portable applications.

10.2 Functional Block Diagram

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