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LM3876 Overture Audio Power Amplifier SeriesHigh-Performance 56W Audio Power Amplifier w/Mute
August 2000
LM3876 Overture ™
Audio Power Amplifier Series
High-Performance 56W Audio Power Amplifier w/Mute
General Description
The LM3876 is a high-performance audio power amplifier
capable of delivering 56W of continuous average power to
an 8
W
n 100W instantaneous peak output power capability
n Signal-to-Noise Ratio ³ 95 dB(min)
n An input mute function
n Output protection from a short to ground or to the
supplies via internal current limiting circuitry
n Output over-voltage protection against transients from
inductive loads
n Supply under-voltage protection, not allowing internal
biasing to occur when |V EE |+|V CC | £ 12V, thus
eliminating turn-on and turn-off transients
n 11-lead TO-220 package
n Wide supply range 20V - 94V
load with 0.1% THD+N from 20Hz–20kHz.
The performance of the LM3876, utilizing its Self Peak In-
stantaneous Temperature (˚Ke) ( SPiKe ™ ) protection cir-
cuitry, puts it in a class above discrete and hybrid amplifiers
by providing an inherently, dynamically protected Safe Oper-
ating Area (SOA). SPiKe protection means that these parts
are completely safeguarded at the output against overvolt-
age, undervoltage, overloads, including shorts to the sup-
plies, thermal runaway, and instantaneous temperature
peaks.
The LM3876 maintains an excellent signal-to-noise ratio of
greater than 95dB (min) with a typical low noise floor of
2.0µV. It exhibits extremely low THD+N values of 0.06% at
the rated output into the rated load over the audio spectrum,
and provides excellent linearity with an IMD (SMPTE) typical
rating of 0.004%.
Applications
n Component stereo
n Compact stereo
n Self-powered speakers
n Surround-sound amplifiers
n High-end stereo TVs
Typical Application
DS011832-1
*Optional components dependent upon specific design requirements. Refer to the External Components Description section for a component functional
description.
FIGURE 1. Typical Audio Amplifier Application Circuit
Overture ™ and SPiKe ™ Protection are trademarks of National Semiconductor Corporation.
© 2000 National Semiconductor Corporation
DS011832
www.national.com
Features
n 56W continuous average output power into 8
W
Connection Diagram
Plastic Package (Note 11)
DS011832-2
† Connect Pin 5 to V + for Compatibility with LM3886.
Top View
Order Number LM3876T
or LM3876TF
See NS Package Number TA11B for
Staggered Lead Non-Isolated
Package or TF11B for
Staggered Lead Isolated Package
www.national.com
2
Absolute Maximum Ratings (Notes 4, 5)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage |V + |+|V − | (No Signal)
Storage Temperature
−40˚C to +150˚C
Thermal Resistance
q JC
1˚C/W
q JA
43˚C/W
94V
Operating Ratings (Notes 4, 5)
Supply Voltage |V + |+|V − | (Input Signal)
84V
Common Mode Input Voltage
(V + or V − ) and
|V + |+|V − |
Temperature Range
T MIN
80V
+85˚C
Supply Voltage |V + |+|V − | 24V to 84V
Note 1: Operation is guaranteed up to 84V, however, distortion may be intro-
duced from SPiKe Protection Circuitry when operating above 70V if proper
thermal considerations are not taken into account. Refer to the Thermal
Considerations section for more information.
(See SPiKe Protection Response)
£
T A
£
T MAX
−20˚C
£
T A
£
Differential Input Voltage
60V
Output Current
Internally Limited
Power Dissipation (Note 6)
125W
ESD Susceptibility (Note 7)
3000V
Junction Temperature (Note 8)
150˚C
Soldering Information
T Package (10 seconds)
260˚C
Electrical Characteristics (Notes 4, 5)
The following specifications apply for V +
= +35V, V −
= −35V, I MUTE = −0.5 mA with R L =8 W unless otherwise specified. Limits
apply for T A = 25˚C.
Symbol
Parameter
Conditions
LM3876
Units
(Limits)
Typical Limit
(Note 9) (Note 10)
|V + |+|V − | Power Supply Voltage (Note 13)
V pin7 −V −
³ 9V
18
24
V (min)
84
V (max)
A M
Mute Attenuation
Pin 8 Open or at 0V, Mute: On
Current out of Pin 8 > 0.5 mA,
120
80
dB (min)
Mute: Off
P O
(Note 3)
Output Power (Continuous Average)
THD + N = 0.1% (max)
56
40
W (min)
f = 1 kHz; f = 20 kHz
Peak P O
Instantaneous Peak Output Power
100
W
THD + N
Total Harmonic Distortion Plus Noise
40W, 20 Hz
£
f
£
20 kHz
0.06
%
A V =26dB
SR
(Note 3)
Slew Rate (Note 12)
V IN = 1.2 Vrms, f = 10 kHz,
11
5
V/µs
(min)
Square-Wave, R L =2k W
I + (Note 2) Total Quiescent Power Supply
Current
V CM = 0V, V o = 0V, I o = 0A, I mute = 0A
30
70
mA (max)
V OS
(Note 2)
Input Offset Voltage
V CM = 0V, I o = 0 mA
1
15
mV (max)
I B
Input Bias Current
V CM = 0V, I o = 0 mA
0.2
1
µA (max)
I OS
Input Offset Current
V CM = 0V, I o = 0 mA
0.01
0.2
µA (max)
I o
Output Current Limit
|V + |=|V − | = 12V, t ON = 10 ms, V O = 0V
6
4
A (min)
V od
(Note 2)
Output Dropout Voltage (Note 14)
|V + –V O |, V +
= 20V, I o = +100 mA
1.6
5
V (max)
|V O –V − |, V −
= −20V, I o = −100 mA
2.7
5
V (max)
PSRR
(Note 2)
Power Supply Rejection Ratio
V +
= 40V to 20V, V −
= −40V,
120
85
dB (min)
V CM = 0V, I o =0mA
V + = 40V, V −
= −40V to −20V,
120
85
dB (min)
V CM = 0V, I o =0mA
CMRR
(Note 2)
Common Mode Rejection Ratio
V +
= 60V to 20V, V −
= −20V to −60V,
120
80
dB (min)
V CM = 20V to −20V, I o =0mA
A VOL
(Note 2)
Open Loop Voltage Gain
|V + |=|V − | = 40V, R L =2k
W
,
D
V O = 60V
120
90
dB (min)
GBWP
Gain-Bandwidth Product
|V + |=|V − | = 40V
8
2
MHz
(min)
f O = 100 kHz, V IN = 50 mVrms
3
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£
Electrical Characteristics (Notes 4, 5) (Continued)
The following specifications apply for V +
= +35V, V −
= −35V, I MUTE = −0.5 mA with R L =8 W unless otherwise specified. Limits
apply for T A = 25˚C.
Symbol
Parameter
Conditions
LM3876
Units
(Limits)
Typical Limit
(Note 9) (Note 10)
e IN
(Note 3)
Input Noise
IHF — A Weighting Filter
2.0
8
µV (max)
R IN = 600
W
(Input Referred)
SNR
Signal-to-Noise Ratio
P O = 1W, A-Weighted,
98
dB
Measured at 1 kHz, R S =25
W
P O = 40W, A-Weighted,
114
dB
Measured at 1 kHz, R S =25 W
Ppk= 100W, A-Weighted,
122
dB
Measured at 1 kHz, R S =25
W
IMD
Intermodulation Distortion Test
60 Hz, 7 kHz, 4:1 (SMPTE)
0.004
%
60 Hz, 7 kHz, 1:1 (SMPTE)
0.006
Note 2: DC Electrical Test; refer to Test Circuit #1.
Note 3: AC Electrical Test; refer to Test Circuit # 2.
Note 4: All voltages are measured with respect to the GND pin (pin 7), unless otherwise specified.
Note 5: 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 6: For operating at case temperatures above 25˚C, the device must be derated based on a 150˚C maximum junction temperature and a thermal resistance of
q JC = 1.0 ˚C/W (junction to case). Refer to the Thermal Resistance figure in the Application Information section under Thermal Considerations.
Note 7: Human body model, 100 pF discharged through a 1.5 k
W
potential when the LM3876 is directly
mounted to the heat sink using only thermal compound. If a mica washer is used in addition to thermal compound,
q
CS (case to sink) is increased, but the heat sink
will be isolated from V − .
Note 12: The feedback compensation network limits the bandwidth of the closed-loop response and so the slew rate will be reduced due to the high frequency
roll-off. Without feedback compensation, the slew rate is typically 16V/µs.
Note 13: V − must have at least −9V at its pin with reference to ground in order for the under-voltage protection circuitry to be disabled.
Note 14: The output dropout voltage is the supply voltage minus the clipping voltage. Refer to the Clipping Voltage vs Supply Voltage graph in the Typical Perfor-
mance Characteristics section.
Test Circuit # 1 (DC Electrical Test Circuit)
DS011832-3
www.national.com
4
resistor.
Note 8: The operating junction temperature maximum is 150˚C, however, the instantaneous Safe Operating Area temperature is 250˚C.
Note 9: Typicals are measured at 25˚C and represent the parametric norm.
Note 10: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 11: The LM3876T package TA11B is a non-isolated package, setting the tab of the device and the heat sink at V −
Test Circuit #2 (AC Electrical Test Circuit)
DS011832-4
Single Supply Application Circuit
DS011832-5
* Optional components dependent upon specific design requirements. Refer to the External
Components Description section for a component functional description.
FIGURE 2. Typical Single Supply Audio Amplifier Application Circuit
5
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