National Semiconductor LM4756 Technical data

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LM4756
Dual 7W Audio Power Amplifier w/Mute, Standby and
Volume Control

LM4756 Dual 7W Audio Power Amplifier w/Mute, Standby and Volume Control

September 2003

General Description

The LM4756 is a stereo audio amplifier capable of delivering
7W/channel at 10% distortion into a 4Ω or 8Ω load. The
power amp has an internally set gain of 30dB. A 0V–5V DC
controlled volume block provides 80dB of attenuation from
input to line-out. Line outputs are available after the volume
control for signal routing.

The amplifier has a smooth transition fade-in/out mute and a
power conserving standby function which are controlled
through TTL or CMOS logic. Both functions provide over
75dB of attenuation.

The LM4756 maintains an excellent Signal-to-Noise ratio of
greater than 70dB with a low noise floor less than 2mV. The
IC also maintains above 50dB of channel separation.

The LM4756 is available in a 15-lead non-isolated plastic
package and is designed for use in TV applications requiring
single supply operation.

Connection Diagrams

Plastic Package Plastic Package

Key Specifications

n Output power into 4Ω or 8Ω at 10% THD 7W (typ)
n Maximum operating voltage 28V (max)
n Power output stage Noise floor 2mV (typ)
n Line output Noise floor 55µV (typ)
n 0V–5V DC controlled volume attenuation 80dB (typ)
n Mute attenuation 75dB (typ)
n Standby-mode supply current 7mA (typ)

Features

n Quiet fade-in/out mute function
n Stereo variable line-out pins
n AC output short circuit protection
n Thermal shutdown protection

Applications

n Audio amplifier for stereo TVs
n Audio amplifier component stereo
n Audio amplifier compact stereo

Top View

U - Wafer Fab Code

Z - Assembly Plant Code

Top View

20064433

Order Number LM4756TA

See NS Package Number TA15A

90 Degree Lead Bend

Order Number LM4756TA Spec. LB10

See NS Package Number TA15D

© 2003 National Semiconductor Corporation DS200644 www.national.com

XY - Date Code

TT - Die Traceability

LM4756TA - LM4756TA

20064444

Typical Application

LM4756

20064401

FIGURE 1. Typical Audio Amplifier Application Circuit

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LM4756

Absolute Maximum Ratings (Notes 3,

4)

If Military/Aerospace specified devices are required,

T Package (10 sec) 260˚C

Storage Temperature −40˚C to +150˚C

Input Signal Voltage Range

please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage 30V

Output Current Internally Limited

Power Dissipation (Note 5) 22W

ESD Susceptibility (Note 6) 2000V

ESD Susceptibility (Note 7) 250V

Junction Temperature 150˚C

Operating Ratings (Notes 3, 4)

Temperature Range

T

≤ TA≤ T

MIN

MAX

Supply Voltage 15V to 28V

θ

(Junction to Ambient) 35˚C/W

JA

θ

(Junction to Case) 1.5˚C/W

JC

−40˚C ≤ TA≤ +85˚C

Soldering Information

Electrical Characteristics (Notes 3, 4)

The following specifications apply for VCC= +22V, and Volume at 0dB unless otherwise specified. Limits apply for TA= 25˚C.

LM4756

Symbol Parameter Conditions

I

CQ

Total Quiescent Power Supply Current V

= 0V, Vo= 0V, Io= 0 mA 20 mA (min)

CM

(Note 1)

I

STBY

Standby Current V

= 5V, Standby-on 7 10 mA (max)

STDBY

(Note 1)

I

MUTE

A

M

(Note 2)

Mute Current V

Mute Attenuation V

= 5V Mute-on 13 20 mA

MUTE

MUTE

= 5V, V

STDBY

= 0V. Mute-on

Signal Input

V

MUTE

= 0V. V

STDBY

= 0V. Mute-off

2 Vrms

Volume Attenuation Range 80 70 dB (min)

Volume Absolute Attenuation
Line-out

@

Pin 3

0V=80dB,2V=14dB,

3V=8dB,4V=3dB,5V=0dB

Line-out Offset Voltage 20 55 mV (max)

P

O

(Note 1)

THD+N

Output Power (Continuous Average) THD+N = 10% (max)

Total Harmonic Distortion Plus Noise P

f = 1 kHz, R

f = 1 kHz, R

=1W,f=1kHz, RL=8Ω 0.4 1 % (max)

o

=4Ω,VCC= 18V 7 W

L

=8Ω,VCC= 22V 7 6.0 W(min)

L

(Note 2)

Xtalk

Channel Separation f = 1 kHz, Po= 5W, RL=8Ω 50 dB

(Note 2)

Power Amp Closed-Loop Gain Error Internal Gain = 30 dB 0.5

SR

Slew Rate V

= 100 mVp-p, t

IN

RISE

(Note 2)

R

IN

Input Impedance 32 kΩ

(Note 1)

I

O

Output Current Limit V

= 100 mV DC, tON= 1 ms, RL=1Ω 2.5 2.0 A(min)

IN

(Note 1)

PSRR
(Note 2)

GBWP Gain-Bandwidth Product f

Power Supply Rejection Ratio Vpin 13 AC = 1 Vrms, f = 100 Hz 50 dB

V

= 0V, Io=0mA

CM

= 100 kHz, VIN= 50 mvrms 2 MHz

o

Power Bandwidth −3 dB Bandwidth at 5W 90 kHz

eVCA

e

out

VCA Output Noise IHF - A Weighting Filter

out

=25Ω

R

IN

Power Amp Output Noise IHF - A Weighting Filter

=25Ω

R

IN

= 2 ns, RL=8Ω 3 V/µs

Typical

(Note 8)

Limit

(Note 9)

(Limits)

80 140 mA (max)

75 60 dB (min)

±

5dB

±

3

±

5 dB (max)

±

1 dB (max)

55 µV

1.8 mV

±

3V

Units

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Electrical Characteristics (Notes 3, 4) (Continued)

The following specifications apply for VCC= +22V, and Volume at 0dB unless otherwise specified. Limits apply for TA= 25˚C.

LM4756

Symbol Parameter Conditions

SNR Signal-to-Noise Ratio Measured at 1 kHz, R

P

= 4.8W, A - Weighted, 70 dB

o

Standby

V

IL

V

IH

Standby Low Input Voltage 0.8 V (max)

Standby High Input Voltage 2.0 V (min)

Mute

V

IL

V

IH

Note 1: DC Electrical Test.

Note 2: AC Electrical Test.

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
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 4: All voltages are measured with respect to the ground (pin 8), unless otherwise specified.

Note 5: The maximum power dissipation must be derated at elevated temperatures and is dictated by T

allowable power dissipation is PDMAX = (T
temperatures above 25˚C, the device must be derated based on a 150˚C maximum junction temperature and a thermal resistance of θ
case).

Note 6: Human body model, 100pF discharged through a 1.5kΩ resistor.

Note 7: Machine model, 200pF–240pF discharge through all pins.

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

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

Note 10: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.

Mute Low Input Voltage 0.8 V (max)

Mute High Input Voltage 2.0 V (min)

)/θJAor the number given in the Absolute Maximum Ratings, whichever is lower. For operating at case

JMAX-TA

=25Ω

s

, θJA, and the ambient temperature, TA. The maximum

JMAX

LM4756

Typical

(Note 8)

Limit

(Note 9)

= 1.5˚C/W (junction to

JC

Units

(Limits)

Standby Mute Pin Function Table

Standby (Pin 9) Mute (Pin 10) Operating Condition

“L” or Open “L” Play

“L” or Open “H” or Open Mute

“H” “L” Standby

“H” “H” or Open Standby

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Typical Performance Characteristics

THD+N vs Frequency

V

CC

= 18V, P

=4Ω, 80kHz BW

R

L

= 1W/Channel

OUT

LM4756

THD+N vs Frequency,

THD+N vs Output Power

= 18V, f = 1kHz

V

CC

=4Ω, 80kHz BW

R

L

Output Power vs

Supply Voltage

f = 1kHz, R

=4Ω, 80kHz BW

L

20064449

20064450

20064412

THD+N vs Output Power

20064418

Output Power vs

Supply Voltage

f = 1kHz, RL=8Ω, 80kHz BW

20064439 20064438

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Typical Performance Characteristics (Continued)

LM4756

Power Dissipation vs

Output Power

Channel Separation vs

Frequency

20064421

Power Dissipation vs

Output Power

20064422

Attenuation vs

Frequency

Volume Attenuation vs

DC Voltage

20064423

20064425

20064424

Supply Current vs

Supply Voltage

20064437

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