LM4884 Datasheet, PDF(1/22 Page) National Semiconductor (TI) – 2.1W Differential Input, BTL Output Stereo Audio Amplifier with RF Suppression and Shutdown

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LM4884 Datasheet, PDF (1/22 Pages) National Semiconductor (TI) – 2.1W Differential Input, BTL Output Stereo Audio Amplifier with RF Suppression and Shutdown

April 2005

LM4884

2.1W Differential Input, BTL Output Stereo Audio

Amplifier with RF Suppression and Shutdown

General Description

The LM4884 features differential stereo inputs, BTL (bridge-

tied load) outputs, and four externally selectable fixed gains.

The LM4884 also features proprietary internal circuitry that

suppresses the coupling of RF signals into the chip. This is

important because certain types of RF signals (such as

GSM) can couple into audio amplifiers in such a way that

part of the signal is heard through the speaker. The RF

suppression circuitry in the LM4884 makes it well-suited for

notebook and portable applications in which strong RF sig-

nals generated by an antenna from a PC wireless card or a

cellular phone may couple audibly into the amplifier.

Operating on a single 5V supply, the LM4884 delivers 1.2W,

1.9W, or 2.1W (typ) of output power to an 8â¦, 4â¦, or 3â¦ BTL

load (Note 1), respectively, with less than 1% THD+N. The

LM4884âs gain is selected using two digital inputs. The nomi-

nal gain values are 6dB, 10dB, 15.6dB, and 21.6dB.

Other features of the LM4884 are that it delivers high-quality

output power from a surface-mount package, requires few

external components, has an active-low micropower shut-

down mode input, and has thermal shutdown protection.

Key Specifications

j BTL output power

RL = 3â¦, VDD = 5.0V, and THD+N = 1%

j BTL output power

RL = 4â¦, VDD = 5.0V, and THD+N = 1%

2.1W (typ)

1.9W (typ)

j BTL output power

RL = 8â¦, VDD = 5.0V, and THD+N = 1%

j Micropower shutdown current

j PSRR (@ 1kHz, VDD = 5V, (Fig.1))

1.2W (typ)

0.1ÂµA (typ)

62dB (typ)

Features

n Improved RF immunity, by up to 28dB over previous

designs (such as the LM4874) in selected applications.

n Fully differential input and output

n Internal gain set: 6dB, 10dB, 15.6dB, and 21.6dB

n Improved "click and pop" suppression

n Thermal shutdown protection circuit

n Ultra low current micropower shutdown mode

n 3.0V to 5.5V operation

n Available in space-saving exposed-DAP TSSOP

package

Applications

n Notebook computers

n PDAs

n Portable electronic devices

Connection Diagram

Top View

20116302

Order Number LM4884MH

See NS Package Number MXA20A for Exposed-DAP TSSOP

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