NSC LM4874MH Datasheet

LM4874

2.1W Differential Input, BTL Output Stereo Audio
Amplifier with Selectable Gain and Shutdown

August 2002

LM4874 Boomer 2.1W Differential Input, BTL Output Stereo Audio Amplifier with Selectable Gain

and Shutdown

General Description

The LM4874 features differential stereo inputs, BTL (bridge­tied load) outputs, and four externally selectable fixed gains.
Operating on a single 5V supply, the LM4874 delivers 1.2W,

1.9W, or 2.1W (typ) of output power to an 8Ω,4Ω,or3Ω BTL
load (Note 1), respectively, with less than 1% THD+N. The
LM4874’s gain is selected using two digital inputs. The nomi­nal gain values are 6dB, 10dB, 15.6dB, and 21.6dB.

The LM4874 is designed for notebook and other handheld
portable applications. It delivers high quality output power
from a surface-mount package and requires few external
components.

Other features include an active-low micropower shutdown
mode input and thermal shutdown protection.

Key Specifications

j

BTL output power

R

=3Ω,VDD= 5.0V, and THD+N = 1% 2.1W (typ)

L

j

BTL output power

R

=4Ω,VDD= 5.0V, and THD+N = 1% 1.9W (typ)

L

Connection Diagram

Top View

j

BTL output power

R

=8Ω,VDD= 5.0V, and THD+N = 1% 1.2W (typ)

L

j

Micropower shutdown current 0.1µA (typ)

j

PSRR (@1kHz, VDD= 5V, (Fig.1)) 62dB (typ)

Features

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

Order Number LM4874MH

See NS Package Number MXA20A for Exposed-DAP TSSOP

Boomer®is a registered trademark of National Semiconductor Corporation.

© 2002 National Semiconductor Corporation DS200469 www.national.com

20046902

Typical Application

LM4874

FIGURE 1. Typical Audio Amplifier Application Circuit

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20046901

LM4874

Absolute Maximum Ratings (Notes 2,

3)

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

Power Dissipation (Note 4) Internally Limited

ESD Susceptibility (Note 5) 2000V

ESD Susceptibility (Note 6) 200V

Junction Temperature 150˚C

Soldering Information

DD

+ 0.3V

Infrared (15 sec.) 220˚C

See AN-450 “Surface Mounting and their Effects on
Product Reliability” for other methods of soldering surface
mount devices.

Thermal Resistance

θ

(typ) MXA20A 2˚C/W

JC

θ

(typ) MXA20A 41˚C/W (Note 7)

JA

Operating Ratings

Temperature Range

≤ TA≤T

T

MIN

MAX

Supply Voltage 3.0 V ≤ V

−40˚C ≤ TA ≤ 85˚C

≤ 5.5V

DD

Small Outline Package

Vapor Phase (60 sec.) 215˚C

Electrical Characteristics for LM4874 (Notes 2, 8)

The following specifications applies to the LM4874 when used in the circuit shown in Figure 1 and operating with VDD=5Vand

= 6dB, unless otherwise specified. Limits apply for TA= 25˚C.

A

V

LM4874

Symbol Parameter Conditions

V

DD

Supply Voltage 3.0

Typical

(Note 8)

Limit

(Notes 9,

10)

5.5

I

DD

I

SD

V

OS

Quiescent Power Supply Current VIN= 0V, IO= 0A, RL=

Shutdown Current V

Output Offset Voltage 7 50 mV (max)

PSRR Output Supply Rejection Ratio V

P

O

Output Power (Note 11) THD+N = 1% (max), f = 1kHz (Note12)

shutdown

DD

= GND 0.1 1.0 µA (max)

= 5V, V

sinewave, C

=8Ω

R

L

=3Ω

R

L

=4Ω

R

L

=8Ω

R

L

RIPPLE

BYPASS

∞

= 200mV

= 0.47µF,

P-P

9.0 12.0 mA (max)

62 dB

2.1

1.9

1.2 1.0

THD+N = 10% (max), f = 1kHz
(Note12)

=3Ω

R

L

=4Ω

R

L

=8Ω

R

L

2.6

2.6

1.5

THD+N Total Harmonic Distortion + Noise 20Hz ≤ f ≤ 20kHz

=4Ω,PO=2W

R

L

=8Ω,PO=1W

R

L

S/N Signal-to-Noise Ratio f = 1kHz, C

= 1.1W, RL=8Ω

P

O

R

IN

Note 1: An LM4874MH that has been properly mounted to a circuit board with a copper heatsink area of at least 2in2will deliver 1.9W into 4Ω or 2.1W into 3Ω.

Note 2: All voltages are measured with respect to the GND pin unless other wise specified.

Note 3: 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 that
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 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θ
allowable power dissipation is P
currents for more information.

Note 5: Human body model, 100 pF discharged through a 1.5 kΩ resistor.

Input Resistance Pins 5, 7, 9, and 17 See Table 1.

DMAX

=(T

JMAX-TA/θJA

or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4874, see power derating

BYPASS

= 0.47µF,

JA

0.3

0.3

97 dB

, and the ambient temperature, TA. The maximum

Units

(Limits)

V (min)

V (max)

W
W

W (min)

W
W
W

%
%

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Electrical Characteristics for LM4874 (Notes 2, 8) (Continued)

Note 6: Machine Model, 220pF-240pF discharged through all pins.

LM4874

Note 7: The given θ

driving 4Ω loads from a 5V supply, the LM4874MH must be mounted to the circuit board and its exposed-DAP soldered to an exposed 2in

Note 8: Typicals are measured at 25˚C and represent the parametric norm.

Note 9: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 10: Datasheet minimum and maximum specification limits are guaranteed by design, test, or statistical analysis.

Note 11: Output power is measured at the amplifier’s package pins.

Note 12: When driving 3Ω or 4Ω loads and operating on a 5V supply, the LM4874MH must be mounted to a circuit board that has a minimum of 2in

uninterrupted copper area connected to the MH package’s exposed DAP.

is for an LM4874 packaged in an MXA20A with the exposed-DAP soldered to an exposed 2in2area of 1oz printed circuit board copper. When

JA

External Components Description

See Figure 1.

Components Functional Description

1. C

2. C

The input coupling capacitor blocks DC voltage at the amplifier’s inverting input terminals. Ci, along with the

i

LM4874’s variable input resistance R
inverting and noninverting inputs require a C
EXTERNAL COMPONENTS, for an explanation of determining the value of C

The supply bypass capacitor. Refer to the POWER SUPPLY BYPASSING section for information about

S

(See Table 1), creates a highpass filter with fC= 1/(2πRiCi). Both

1

. Refer to the Application Information section, SELECTING

i

.

i

properly placing, and selecting the value of, this capacitor.

3. C

The capacitor, CB, filters the half-supply voltage present on the BYPASS pin. Refer to the Application

B

Information section, SELECTING EXTERNAL COMPONENTS, for information concerning proper placement
and selecting C

’s value.

B

Typical Performance Characteristics MH Specific Characteristics

2

area of 1oz PCB copper.

2

of exposed,

THD vs Frequency THD vs Frequency

VDD= 5V, RL=4Ω,P

= 1000mW,

OUT

at (from top to bottom at 1kHz):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

20046998

VDD= 5V, RL=8Ω,P

OUT

= 400mW,

at (from top to bottom at 1kHz):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

20046997

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Typical Performance Characteristics
MH Specific Characteristics

THD vs Frequency THD vs Frequency

(Continued)

LM4874

VDD= 5V, RL=8Ω,P

OUT

= 400mW,

at (from top to bottom at 1kHz):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

THD vs Frequency THD vs Frequency

VDD= 5V, RL=3Ω,fIN= 1kHz,

at (from top to bottom at 50mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

20046999

20046944

VDD= 5V, RL=3Ω,fIN= 20Hz,

at (from top to bottom at 50mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

VDD= 5V, RL=3Ω,fIN= 20kHz,

at (from top to bottom at 50mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

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20046945

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Typical Performance Characteristics
MH Specific Characteristics

LM4874

THD vs Output Power THD vs Output Power

(Continued)

VDD= 5V, RL=4Ω,fIN= 20Hz,

at (from top to bottom at 100mW):

= 21.6dB, AV= 15.6dB,

A

V

= 6dB, AV= 10dB

A

V

200469A0

VDD= 5V, RL=4Ω,fIN= 1kHz,

at (from top to bottom at 200mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

THD vs Output Power THD vs Output Power

VDD= 5V, RL=4Ω,fIN= 20kHz,

at (from top to bottom at 200mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

200469A2

VDD= 5V, RL=8Ω,fIN= 20Hz,

at (from top to bottom at 200mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

200469A1

200469A3

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Typical Performance Characteristics
MH Specific Characteristics

THD vs Output Power THD vs Output Power

(Continued)

LM4874

VDD= 5V, RL=8Ω,fIN= 1kHz,

at (from top to bottom at 200mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

200469A4

VDD= 5V, RL=8Ω,fIN= 20kHz,

at (from top to bottom at 200mW):

= 21.6dB, AV= 15.6dB,

A

V

= 10dB, AV= 6dB

A

V

Output Power vs Supply Voltage Output Power vs Supply Voltage

RL=4Ω,fIN= 1kHz,

at (from top to bottom at 4V):

THD+N = 10%, THD+N = 1%

200469C3

RL=8Ω,fIN= 1kHz,

at (from top to bottom at 4V):

THD+N = 10%, THD+N = 1%

200469A5

200469C4

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