LM4871
3W Audio Power Amplifier with Shutdown Mode

General Description

The LM4871 is a mono bridged audio power amplifier ca-
pable of delivering 3W of continuous average power into a
3

load with less than 10% THD when powered by a 5V

power supply (Note 1). To conserve power in portable appli-
cations, the LM4871's micropower shutdown mode (I

0.6µA, typ) is activated when V

is applied to the SHUT-

DOWN pin.

Boomer audio power amplifiers are designed specifically to
provide high power, high fidelity audio output. They require
few external components and operate on low supply volt-
ages from 2.0V to 5.5V. Since the LM4871 does not require
output coupling capacitors, bootstrap capacitors, or snubber
networks, it is ideally suited for low-power portable systems
that require minimum volume and weight.

Additional LM4871 features include thermal shutdown pro-
tection, unity-gain stability, and external gain set.

Note 1: An LM4871LD that has been properly mounted to a circuit board will
deliver 3W into 3

(at 10% THD). The other package options for the LM4871

will deliver 1.5W into 8

(at 10% THD). See the Application Information

sections for further information concerning the LM4871LD, LM4871MM,
LM4871M, and the LM4871N.

Key Specifications

PO at 10% THD+N, 1kHz

LM4871LD: 3

, 4

loads

3W (typ), 2.5W (typ)

All other LM4871 packages: 8

load

1.5W (typ)

Shutdown current

0.6µA (typ)

Supply voltage range

2.0V to 5.5V

THD at 1kHz at 1W continuous average output power
into 8

0.5% (max)

Features

No output coupling capacitors, bootstrap capacitors, or
snubber circuits required

Unity-gain stable

LLP, MSOP, SO, or DIP packaging

External gain configuration capability

Pin compatible with the LM4861

Applications

Portable computers

Desktop computers

Low voltage audio systems

Typical Application

Connection Diagram

Boomer

is a registered trademark of National Semiconductor Corporation.

DS100008-1

FIGURE 1. Typical Audio Amplifier Application Circuit

MSOP, Small Outline, and DIP Package

DS100008-2

Top View

Order Number LM4871MM, LM4871M, or LM4871N

See NS Package Number MUA08A, M08A, or N08E

LLP Package

DS100008-39

Top View

Order Number LM4871LD

See NS Package Number LDC08A

October 2000

LM4871

Audio

Power

Amplifier

with

Shutdown

Mode

DS100008

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

Supply Temperature

-65°C to +150°C

Input Voltage

-0.3V to V

to +0.3V

Power Dissipation (Note 4)

Internally Limited

ESD Susceptibility (Note 5)

5000V

ESD Susceptibility (Note 6)

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

(typ) -- N08E

37°C/W

(typ) -- N08E

107°C/W

(typ) -- MUA08A

56°C/W

(typ) -- MUA08A

210°C/W

(typ) -- LDC08A

4.3°C/W

(typ) -- LDC08A

56°C/W (Note 9)

Operating Ratings

Temperature Range

MIN

MAX

-40°C

85°C

Supply Voltage

2.0V

5.5V

Electrical Characteristics

(Notes 2, 3)

The following specifications apply for V

= 5V and R

= 8

unless otherwise specified. Limits apply for T

= 25°C.

Sym-

bol

Parameter

Conditions

LM4871

Min

(Note 7)

Typical

(Note 8)

Limit

(Note 7)

Units

(Limits)

Supply Voltage

2.0

5.5

Quiescent Power Supply
Current

= 0V, I

= 0A

6.5

10.0

Shutdown Current

PIN1

= V

0.6

µA

Output Offset Voltage

= 0V

5.0

Output Power

THD = 1%, f = 1kHz

LM4871LD, R

= 3

(Note 10)

LM4871LD, R

= 4

(Note 10)

LM4871, R

= 8

(Note 10)

2.38

1.2

THD+N = 10%, f = 1kHz

LM4871LD, R

= 3

(Note 10)

LM4871LD, R

= 4

(Note 10)

LM4871, R

= 8

(Note 10)

2.5
1.5

THD+N

Total Harmonic
Distortion+Noise

20Hz

20kHz, A

= 2

LM4871LD, R

= 4

, P

= 1.6W

LM4871, R

= 8

, P

= 1W

0.13
0.25

PSRR

Power Supply Rejection
Ratio

= 4.9V to 5.1V

Note 2:

Absolute Maximum Ratings

indicate limits beyond which damage to the device may occur.

Operating Ratings

indicate conditions for which the device is

functional, but do not guarantee specific performance limits.

Electrical Characteristics

state DC and AC electrical specifications under particular test conditions which

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

Note 4: 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 LM4871, T

JMAX

= 150°C. For

the

's for different packages, please see the Application Information section or the Absolute Maximum Ratings section.

Note 5: Human body model, 100pF discharged through a 1.5k

resistor.

Note 6: Machine Model, 220pF240pF discharged through all pins.

Note 7: Typicals are specified at 25°C and represent the parametric norm.

Note 8: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).

Note 9: The given

is for an LM4871 packaged in an LDC08A with the ExposedDAP soldered to an exposed 1in

area of 1oz printed circuit board copper.

Note 10: When driving 3

or 4

loads from a 5V supply, the LM4871LD must be mounted to a circuit board.

LM4871

www.national.com

External Components Description

(

Figure 1)

Components

Functional Description

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

Supply bypass capacitor that 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 that 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
LD Specific Characteristics

Note 11: This curve shows the LM4871LD's thermal dissipation ability at different ambient temperatures given the exposed-DAP of the part is soldered to a plane
of 1oz. Cu with an area given in the label of each curve. This label also designates whether the plane exists on the same (top) layer as the chip, on the bottom layer,
or on both layers. Infinite heatsink and unattached (no heatsink) conditions are also shown.

LM4871LD
THD+N vs Output Power

DS100008-24

LM4871LD
THD+N vs Frequency

DS100008-23

LM4871LD
THD+N vs Frequency

DS100008-25

LM4871LD
THD+N vs Output Power

DS100008-26

LM4871LD
Power Dissipation vs Output Power

DS100008-27

LM4871LD (Note 11)
Power Derating Curve

DS100008-28

LM4871

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