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LM4756
Dual 7W Audio Power Amplifier w/Mute, Standby and
Volume Control
General Description
The LM4756 is a stereo audio amplifier capable of delivering
7W/channel at 10% distortion into a 4
or 8 load. The
power amp has an internally set gain of 30dB. A 0V5V 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.
Key Specifications
n
Output power into 4
or 8 at 10% THD
7W (typ)
n
Maximum operating voltage
28V (max)
n
Power output stage Noise floor
2mV (typ)
n
Line output Noise floor
55V (typ)
n
0V5V 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
Connection Diagrams
Plastic Package
Plastic Package
20064433
Top View
Order Number LM4756TA
See NS Package Number TA15A
90 Degree Lead Bend
Order Number LM4756TA Spec. LB10
See NS Package Number TA15D
20064444
Top View
U - Wafer Fab Code
Z - Assembly Plant Code
XY - Date Code
TT - Die Traceability
LM4756TA - LM4756TA
September 2003
LM4756
Dual
7W
Audio
Power
Amplifier
w/Mute,
Standby
and
V
olume
Control
2003 National Semiconductor Corporation
DS200644
www.national.com
Typical Application
20064401
FIGURE 1. Typical Audio Amplifier Application Circuit
LM4756
www.national.com
2
Absolute Maximum Ratings
(Notes 3,
4)
If Military/Aerospace specified devices are required,
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
150C
Soldering Information
T Package (10 sec)
260C
Storage Temperature
-40C to +150C
Input Signal Voltage Range
3V
Operating Ratings
(Notes 3, 4)
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage
15V to 28V
JA
(Junction to Ambient)
35C/W
JC
(Junction to Case)
1.5C/W
Electrical Characteristics
(Notes 3, 4)
The following specifications apply for V
CC
= +22V, and Volume at 0dB unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4756
Units
(Limits)
Typical
(Note 8)
Limit
(Note 9)
I
CQ
(Note 1)
Total Quiescent Power Supply Current
V
CM
= 0V, V
o
= 0V, I
o
= 0 mA
20
mA (min)
80
140
mA (max)
I
STBY
(Note 1)
Standby Current
V
STDBY
= 5V, Standby-on
7
10
mA (max)
I
MUTE
Mute Current
V
MUTE
= 5V Mute-on
13
20
mA
A
M
(Note 2)
Mute Attenuation
V
MUTE
= 5V, V
STDBY
= 0V. Mute-on
Signal Input
75
60
dB (min)
V
MUTE
= 0V. V
STDBY
= 0V. Mute-off
2 Vrms
5
dB
Volume Attenuation Range
80
70
dB (min)
Volume Absolute Attenuation
Line-out
Pin 3
@
0V = 80 dB, 2V = 14 dB,
3V = 8 dB, 4V = 3 dB, 5V = 0 dB
3
5
dB (max)
Line-out Offset Voltage
20
55
mV (max)
P
O
(Note 1)
Output Power (Continuous Average)
THD+N = 10% (max)
f = 1 kHz, R
L
= 4
, V
CC
= 18V
7
W
f = 1 kHz, R
L
= 8
, V
CC
= 22V
7
6.0
W(min)
THD+N
(Note 2)
Total Harmonic Distortion Plus Noise
P
o
= 1W, f = 1 kHz, R
L
= 8
0.4
1
% (max)
Xtalk
(Note 2)
Channel Separation
f = 1 kHz, P
o
= 5W, R
L
= 8
50
dB
Power Amp Closed-Loop Gain Error
Internal Gain = 30 dB
0.5
1
dB (max)
SR
(Note 2)
Slew Rate
V
IN
= 100 mVp-p, t
RISE
= 2 ns, R
L
= 8
3
V/s
R
IN
(Note 1)
Input Impedance
32
k
I
O
(Note 1)
Output Current Limit
V
IN
= 100 mV DC, t
ON
= 1 ms, R
L
= 1
2.5
2.0
A(min)
PSRR
(Note 2)
Power Supply Rejection Ratio
Vpin 13 AC = 1 Vrms, f = 100 Hz
50
dB
V
CM
= 0V, I
o
= 0 mA
GBWP
Gain-Bandwidth Product
f
o
= 100 kHz, V
IN
= 50 mvrms
2
MHz
Power Bandwidth
-3 dB Bandwidth at 5W
90
kHz
eVCA
out
VCA Output Noise
IHF - A Weighting Filter
R
IN
= 25
55
V
e
out
Power Amp Output Noise
IHF - A Weighting Filter
R
IN
= 25
1.8
mV
LM4756
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3
Electrical Characteristics
(Notes 3, 4) (Continued)
The following specifications apply for V
CC
= +22V, and Volume at 0dB unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4756
Units
(Limits)
Typical
(Note 8)
Limit
(Note 9)
SNR
Signal-to-Noise Ratio
Measured at 1 kHz, R
s
= 25
P
o
= 4.8W, A - Weighted,
70
dB
Standby
V
IL
Standby Low Input Voltage
0.8
V (max)
V
IH
Standby High Input Voltage
2.0
V (min)
Mute
V
IL
Mute Low Input Voltage
0.8
V (max)
V
IH
Mute High Input Voltage
2.0
V (min)
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
JMAX
,
JA
, and the ambient temperature, T
A
. The maximum
allowable power dissipation is PDMAX = (T
JMAX
- T
A
)/
JA
or the number given in the Absolute Maximum Ratings, whichever is lower. For operating at case
temperatures above 25C, the device must be derated based on a 150C maximum junction temperature and a thermal resistance of
JC
= 1.5C/W (junction to
case).
Note 6: Human body model, 100pF discharged through a 1.5k
resistor.
Note 7: Machine model, 200pF240pF discharge through all pins.
Note 8: Typicals are measured at 25C 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.
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
LM4756
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4
Typical Performance Characteristics
THD+N vs Frequency
V
CC
= 18V, P
OUT
= 1W/Channel
R
L
= 4
, 80kHz BW
THD+N vs Frequency,
20064449
20064412
THD+N vs Output Power
V
CC
= 18V, f = 1kHz
R
L
= 4
, 80kHz BW
THD+N vs Output Power
20064450
20064418
Output Power vs
Supply Voltage
f = 1kHz, R
L
= 4
, 80kHz BW
Output Power vs
Supply Voltage
f = 1kHz, R
L
= 8
, 80kHz BW
20064439
20064438
LM4756
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5
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