LM4867

Output-Transient-Free Dual 2.1W Audio Amplifier Plus

No Coupling Capacitor Stereo Headphone Function

General Description

The LM4867 is a dual bridge-connected audio power ampli-

fier which, when connected to a 5V supply, will deliver 2.1W

toa4

Ω load (Note 1) or 2.4W to a 3Ω load (Note 2) with less

than 1.0% THD+N. The LM4867 uses advanced, latest gen-

eration circuitry to eliminate all traces of clicks and pops

when the supply voltage is first applied. The amplifier has a

headphone-amplifier-select input pin. It is used to switch the

amplifiers from bridge to single-ended mode for driving

headphones. A new circuit topology eliminates headphone

output coupling capacitors. A MUX control pin allows selec-

tion between the two sets of stereo input signals. The MUX

control can also be used to select between two different

customer-specified closed-loop responses.

Boomer audio power amplifiers are designed specifically to

provide high quality output power from a surface mount

package and require few external components. To simplify

audio system design, the LM4867 combines dual bridge

speaker amplifiers and stereo headphone amplifiers in one

package.

The LM4867 features an externally controlled power-saving

micropower shutdown mode, a stereo headphone amplifier

mode, and thermal shutdown protection.

Note 1: An LM4867LQ or LM4867MTE that has been properly mounted to

a circuit board will deliver 2.1W into 4

Ω. The Mux control can also be used to

select two different closed-loop responses. LM4867MT will deliver 1.1W into

8

Ω. See the Application Information sections for further information concern-

ing the LM4867LQ and the LM4867MT.

Note 2: An LM4867LQ or LM4867MTE that has been properly mounted to a

circuit board and forced-air cooled will deliver 2.4W into 3

Ω.

Key Specifications

n

P

n

LM4867LQ, 3

Ω load

2.4W (typ)

n

LM4867LQ, 4

Ω load

2.1W (typ)

n

LM4867MTE, 4

Ω

1.9W (typ)

n

LM4867MT, 8

Ω

1.1W (typ)

n

Single-ended mode - THD+N at 75mW into 32

Ω

0.5%

(max)

n

Shutdown current

0.7µA (typ)

Features

n

Advanced “click and pop” suppression circuitry

n

Eliminates headphone amplifier output coupling

capacitors

n

Stereo headphone amplifier mode

n

Input mux control and two separate inputs per channel

n

Thermal shutdown protection circuitry

n

LLP, TSSOP, and exposed-DAP TSSOP packaging

available

Applications

n

Multimedia monitors

n

Portable and desktop computers

n

Portable audio systems

Typical Application

DS200013-31

FIGURE 1. Typical Audio Amplifier Application Circuit

(Pin out shown for the 24-pin Exposed-DAP LLP package. Numbers in ( ) are for the 20-pin MTE and MT

packages.)

February 2001

© 2001 National Semiconductor Corporation

DS200013

www.national.com