LM4876
1.1W Audio Power Amplifier with Shutdown Logic Low

General Description

The LM4876 is a bridge-connected audio power amplifier ca-
pable of delivering typically 1.1W of continuous average
power to an 8

load with 0.5% (THD) from a 5V power sup-

ply.

Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. Since the LM4876 does not require
output coupling capacitors, bootstrap capacitors, or snubber
networks, it is optionally suited for low-power portable sys-
tems.

The LM4876 features an externally controlled, low-power
consumption shutdown mode, which is achieved by driving
pin 1 with logic low. Additionally, the LM4876 features an in-
ternal thermal shutdown protection mechanism.

The LM4876 is unity-gain stable and can be configured by
external gain-setting resistors.

Key Specifications

THD at 1 kHz at 1W continuous

average output power into 8

0.5% (max)

Output power at 10% THD+N

at 1 kHz into 8

1.5W (typ)

Shutdown Current

0.01 µA (typ)

Features

No output coupling capacitors, bootstrap capacitors, or
snubber circuits are necessary

Small Outline packaging

Unity-gain stable

External gain configuration capability

Pin compatible with LM4861 and LM4871

Applications

Mobile Phones

Portable Computers

Desktop Computers

Low Voltage Audio Systems

Typical Application

Connection Diagram

Boomer

is a registered trademark of National Semiconductor Corporation.

DS101299-1

FIGURE 1. Typical Audio Amplifier Application Circuit

Small Outline Package

DS101299-2

Top View

Order Number LM4876M

See NS Package Number M08A

February 2000

LM4876

1.1W

Audio

Power

Amplifier

with

Shutdown

Logic

Low

DS101299

www.national.com

Absolute Maximum Ratings

(Note 2)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage

6.0V

Storage Temperature

-65°C to +150°C

Input Voltage

-0.3V to V

+0.3V

Power Dissipation (Note 3)

Internally Limited

ESD Susceptibility (Note 4)

5000V

ESD Susceptibility (Note 5)

250V

Junction Temperature

150°C

Soldering Information

Small Outline Package

Vapor Phase (60 sec.)

215°C

Infrared (15 sec.)

220°C

See AN-450

Surface Mounting and their Effects on

Product Reliability

for other methods of

soldering surface mount devices.

(typ) -- M08A

35°C/W

(typ) -- M08A

140°C/W

Operating Ratings

Temperature Range

MIN

MAX

-40°C

85°C

Supply Voltage

2.0V

5.5V

Electrical Characteristics

(Notes 1, 2)

The following specifications apply for V

= 5V unless otherwise specified. Limits apply for T

= 25°C.

Symbol

Parameter

Conditions

LM4876

Units

(Limits)

Typical

Limit

(Note 6)

(Note 7)

Supply Voltage

2.0

V (min)

5.5

V (max)

Quiescent Power Supply Current

= 0V, I

= 0A

6.5

10.0

mA (max)

Shutdown Current

PIN1

= 0V

0.01

µA (max)

Output Offset Voltage

= 0V

mV (max)

Output Power

THD = 0.5% (max); f = 1 kHz

1.10

1.0

W (min)

THD+N = 10%; f = 1 kHz

1.5

THD+N

Total Harmonic Distortion+Noise

= 1 Wrms; A

= 2; 20 Hz

20 kHz

0.25

PSRR

Power Supply Rejection Ratio

= 4.9V to 5.1V

Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.

Note 2:

Absolute Maximum Ratings

indicate limits beyond which damage to the device may occur.

Operating Ratings

indicate conditions for which the device is func-

tional, but do not guarantee specific performance limits.

Electrical Characteristics

state DC and AC electrical specifications under particular test conditions which guar-

antee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is
given, however, the typical value is a good indication of device performance.

Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by T

JMAX

, and the ambient temperature T

. The maximum

allowable power dissipation is P

DMAX

= (T

JMAX

or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4876, T

JMAX

= 150°C. The

typical junction-to-ambient thermal resistance is 140°C/W for package number M08A.

Note 4: Human body model, 100 pF discharged through a 1.5 k

resistor.

Note 5: Machine Model, 220 pF240 pF discharged through all pins.

Note 6: Typicals are measured at 25°C and represent the parametric norm.

Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).

Electrical Characteristics V

= 5/3.3/2.6V

Symbol

Parameter

Conditions

LM4876

Units

(Limits)

Typical

Limit

(Note 6)

(Note 7)

Shutdown Input Voltage High

1.2

V(min)

Shutdown Input Voltage Low

0.4

V(max)

LM4876

www.national.com

External Components Description

(

Figure 1)

Components

Functional Description

Inverting input resistance which sets the closed-loop gain in conjunction with R

. This resistor also forms a

high pass filter with C

at f

= 1/(2

Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a
highpass filter with R

at f

= 1/(2

). Refer to the section, Proper Selection of External Components,

for an explanation of how to determine the value of C

Feedback resistance which sets the closed-loop gain in conjunction with R

Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing
section for information concerning proper placement and selection of the supply bypass capacitor.

Bypass pin capacitor which provides half-supply filtering. Refer to the section, Proper Selection of External
Components, for information concerning proper placement and selection of C

Typical Performance Characteristics

THD+N vs Frequency

DS101299-3

THD+N vs Frequency

DS101299-4

THD+N vs Frequency

DS101299-5

THD+N vs Output Power

DS101299-6

THD+N vs Output Power

DS101299-7

THD+N vs Output Power

DS101299-8

Output Power vs
Supply Voltage

DS101299-9

Output Power vs
Supply Voltage

DS101299-10

Output Power vs
Supply Voltage

DS101299-11

LM4876

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