MUX/

GAIN

STAGE

VDD

IN1+

IN1-

SGND

OUT+

OUT-

+2.7V to +5.5V

CS

CBST

BOOST

CONVERTER

ALC

SCL/GAIN

SW

PGND

VBST

L1

SHDN

D1

4.7 PH

1 PF

10:

I2C

INTERFACE

IN2+

IN2-

SDA/SEL

0.47 PF

CIN

CIN

CIN

CIN

SET

SW/HW

0.47 PF

0.47 PF

0.47 PF

RL

CL

LM48560

www.ti.com

SNAS513F – AUGUST 2011 – REVISED NOVEMBER 2015

8 Detailed Description

8.1 Overview

The LM48560 device is a fully differential Class H driver for ceramic speakers and piezo actuators. The

integrated, high efficiency boost converter dynamically adjusts the amplifier’s supply voltage based on the output

signal to maintain sufficient headroom while improving efficiency. The LM48560 device’s Class H architecture

offers significant power savings compared to conventional Class AB drivers. The LM48560 features two fully

differential inputs with separate gain settings, and a selectable control interface. In software control mode, the

gain control and device modes are configured through the I2C interface. In hardware control mode, the gain and

input mux are configured through a pair of logic inputs.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 General Amplifier Function

The LM48560 device is a fully differential, Class H piezo driver for ceramic speakers and haptic actuators. The

integrated, high efficiency boost converter dynamically adjusts the amplifier’s supply voltage based on the output

signal, increasing headroom and improving efficiency compared to a conventional Class AB driver. The fully

differential amplifier takes advantage of the increased headroom and bridge-tied load (BTL) architecture,

delivering significantly more voltage than a single-ended amplifier.

8.3.2 Class H Operation

Class H is a modification of another amplifier class (typically Class B or Class AB) to increase efficiency and

reduce power dissipation. To decrease power dissipation, Class H uses a tracking power supply that monitors

the output signal and adjusts the supply accordingly. When the amplifier output is below 3VP-P, the nominal boost

voltage is 6 V. As the amplifier output increases above 3 VP-P, the boost voltage tracks the amplifier output as

shown in Figure 24. When the amplifier output falls below 3 VP-P, the boost converter returns to its nominal output

voltage. Power dissipation is greatly reduced compared to conventional Class AB drivers.

Copyright © 2011–2015, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Links: LM48560