LM3876.PDF
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LM3876
April 1995
LM3876
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
X
load with 0.1% (THD
a
N) from 20 Hz±20 kHz.
Features
Y
56W continuous average output power into 8
X
Y
100W instantaneous peak output power capability
Y
Signal-to-Noise Ratio
t
95 dB(min)
Y
An input mute function
Y
Output protection from a short to ground or to the sup-
plies via internal current limiting circuitry
Y
Output over-voltage protection against transients from
inductive loads
Y
Supply under-voltage protection, not allowing internal
biasing to occur when
l
V
EE
l
a
l
V
CC
l
s
12V, thus elimi-
nating turn-on and turn-off transients
Y
11-lead TO-220 package
The performance of the LM3876, utilizing its Self Peak In-
stantaneous Temperature (
§
Ke) (SPiKe
TM
) Protection Cir-
cuitry, puts it in a class above discrete and hybrid amplifiers
by providing an inherently, dynamically protected Safe Op-
erating Area (SOA). SPiKe Protection means that these
parts are completely safeguarded at the output against
overvoltage, undervoltage, overloads, including shorts to
the supplies, thermal runaway, and instantaneous tempera-
ture peaks.
The LM3876 maintains an excellent Signal-to-Noise Ratio of
greater than 95 dB(min) with a typical low noise floor of
2.0
m
V. It exhibits extremely low (THD
a
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
Y
Component stereo
Y
Compact stereo
Y
Self-powered speakers
Y
Surround-sound amplifiers
Y
High-end stereo TVs
Typical Application
Connection Diagram
Plastic Package (Note 8)
TL/H/11832±2
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
Connect Pin 5 to V
a
for Compatibility with
LM3886.
TL/H/11832±1
FIGURE 1. Typical Audio Amplifier Application Circuit
*Optional components dependent upon specific design requirements. Refer to the External Compo-
nents Description section for a component functional description.
Overture
TM
and SPiKe
TM
Protection are trademarks of National Semiconductor Corporation.
C
1995 National Semiconductor Corporation
TL/H/11832
RRD-B30M75/Printed in U. S. A.
²
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Supply Voltage
l
V
a
l
a
l
V
b
l
(No Signal)
Soldering Information
T Package (10 seconds)
260
§
C
Storage Temperature
b
40
§
Cto
a
150
§
C
94V
Thermal Resistance
i
JC
Supply Voltage
l
V
a
l
a
l
V
b
l
(Input Signal)
84V
1
§
C/W
Common Mode Input Voltage
(V
a
or V
b
) and
l
V
a
l
a
l
V
b
l
s
80V
i
JA
43
§
C/W
Operating Ratings
(Notes 1, 2)
Temperature Range
T
MIN
s
T
A
s
T
MAX
b
20
§
C
s
T
A
s a
85
§
C
Supply Voltage
l
V
a
l
a
l
V
b
l
24V to 84V
Note: 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)
Differential Input Voltage
60V
Output Current
Internally Limited
Power Dissipation (Note 3)
125W
ESD Susceptibility (Note 4)
3000V
Junction Temperature (Note 5)
150
§
C
Electrical Characteristics
(Notes 1, 2) The following specifications apply for V
a
ea
35V, V
b
eb
35V,
I
MUTE
eb
0.5 mA with R
L
e
8
X
unless otherwise specified. Limits apply for T
A
e
25
§
C.
LM3876
Units
Symbol
Parameter
Conditions
Typical Limit
(Note 6) (Note 7)
(Limits)
l
V
a
l
a
l
V
b
l
Power Supply Voltage (Note 10)
V
pin7
b
V
b
t
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
l
0.5 mA,
120
80 dB (min)
Mute: Off
**P
O
Output Power (Continuous Average) THD
a
N
e
0.1% (max)
56
40 W (min)
f
e
1 kHz; f
e
20 kHz
Peak P
O
Instantaneous Peak Output Power
100
W
THD
a
N Total Harmonic Distortion Plus Noise 40W, 20 Hz
s
f
s
20 kHz
0.06
%
A
V
e
26 dB
**SR
Slew Rate (Note 9)
V
IN
e
1.2 Vrms, f
e
10 kHz,
11
5 V/
m
s (min)
Square-Wave, R
L
e
2k
X
*I
a
Total Quiescent Power Supply Current V
CM
e
0V, V
o
e
0V, I
o
e
0A, I
mute
e
0A
30
70 mA (max)
*V
OS
Input Offset Voltage
V
CM
e
0V, I
o
e
0 mA
1
15 mV (max)
I
B
Input Bias Current
V
CM
e
0V, I
o
e
0 mA
0.2
1
m
A (max)
I
OS
Input Offset Current
V
CM
e
0V, I
o
e
0 mA
0.01
0.2
m
A (max)
I
o
Output Current Limit
l
V
a
l
e
l
V
b
l
e
12V, t
ON
e
10 ms, V
O
e
0V 6
4 A (min)
*V
od
Output Dropout Voltage (Note 11)
l
V
a
±V
O
l
,V
a
e
20V, I
o
ea
100 mA
1.6
5 V (max)
l
V
O
±V
b
l
,V
b
eb
20V, I
o
eb
100 mA
2.7
5 V (max)
*PSRR Power Supply Rejection Ratio
V
a
e
40V to 20V, V
b
eb
40V,
120
85 dB (min)
V
CM
e
0V, I
o
e
0mA
V
a
e
40V, V
b
eb
40V to
b
20V,
120
85 dB (min)
V
CM
e
0V, I
o
e
0mA
*DC Electrical Test; refer to Test Circuit Ý1.
**AC Electrical Test; refer to Test Circuit Ý2.
2
Electrical Characteristics
(Notes 1, 2)
The following specifications apply for V
a
ea
35V, V
b
eb
35V, I
MUTE
eb
0.5 mA with R
L
e
8
X
unless otherwise specified.
Limits apply for T
A
e
25
§
C. (Continued)
LM3876
Units
Symbol
Parameter
Conditions
Typical Limit
(Note 6) (Note 7)
(Limits)
*CMRR Common Mode Rejection Ratio V
a
e
60V to 20V, V
b
eb
20V to
b
60V,
120
80
dB (min)
V
CM
e
20V to
b
20V, I
o
e
0mA
*A
VOL
Open Loop Voltage Gain
l
V
a
l
e
l
V
b
l
e
40V, R
L
e
2k
X
,
D
V
O
e
60V 120
90
dB (min)
GBWP Gain-Bandwidth Product
l
V
a
l
e
l
V
b
l
e
40V
8
2 MHz (min)
f
O
e
100 kHz, V
IN
e
50 mVrms
**e
IN
Input Noise
IHFÐA Weighting Filter
2.0
8
m
V (max)
R
IN
e
600
X
(Input Referred)
SNR Signal-to-Noise Ratio
P
O
e
1W, A-Weighted,
98
dB
Measured at 1 kHz, R
S
e
25
X
P
O
e
40W, A-Weighted,
114
dB
Measured at 1 kHz, R
S
e
25
X
Ppk
e
100W, A-Weighted,
122
dB
Measured at 1 kHz, R
S
e
25
X
IMD Intermodulation Distortion Test 60 Hz, 7 kHz, 4:1 (SMPTE)
0.004
%
60 Hz, 7 kHz, 1:1 (SMPTE)
0.006
*DC Electrical Test; refer to Test Circuit
Ý
1.
**AC Electrical Test; refer to Test Circuit
Ý
2.
Note 1: All voltages are measured with respect to the GND pin (pin 7), unless otherwise specified.
Note 2: AbsoluteMaximumRatings indicate limits beyond which damage to the device may occur. OperatingRatings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. ElectricalCharacteristics 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: 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
i
JC
e
1.0
§
C/W (junction to case). Refer to the Thermal Resistance figure in the Application Information section under Thermal Considerations.
Note 4: Human body model, 100 pF discharged through a 1.5 k
X
resistor.
Note 5: The operating junction temperature maximum is 150
§
C, however, the instantaneous Safe Operating Area temperature is 250
§
C.
Note 6: Typicals are measured at 25
§
C and represent the parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: The LM3876T package TA11B is a non-isolated package, setting the tab of the device and the heat sink at V
b
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,
i
CS
(case to sink) is increased, but the heat sink
will be isolated from V
b
.
Note 9: 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/
m
s.
Note 10: V
b
must have at least
b
9V at its pin with reference to ground in order for the under-voltage protection circuitry to be disabled.
Note 11: The output dropout voltage is the supply voltage minus the clipping voltage. Refer to the Clipping Voltage vs Supply Voltage graph in the Typical
Performance Characteristics section.
3
Test Circuit
Ý
1
*(DC Electrical Test Circuit)
TL/H/11832±3
Test Circuit
Ý
2
**(AC Electrical Test Circuit)
TL/H/11832±4
4
Single Supply Application Circuit
TL/H/11832±5
FIGURE 2. Typical Single Supply Audio Amplifier Application Circuit
*Optional components dependent upon specific design requirements. Refer to the External
Components Description section for a component functional description.
Equivalent Schematic
(excluding active protection circuitry)
TL/H/11832±6
5
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