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National Semiconductor
National Semiconductor

LM3875 Datasheet

LM3875 Overture Audio Power Amplifier Series High-Performance 56W Audio Power Amplifier


LM3875 Datasheet Preview


June 1999
LM3875 OvertureAudio Power Amplifier Series
High-Performance 56W Audio Power Amplifier
General Description
The LM3875 is a high-performance audio power amplifier
capable of delivering 56W of continuous average power to
an 8load with 0.1% (THD + N) from 20 Hz–20 kHz.
The performance of the LM3875, 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 LM3875 maintains an excellent Signal-to-Noise Ratio of
greater than 95 dB(min) with a typical low noise floor of
2.0 µV. It exhibits extremely low (THD + N) values of 0.06%
at the rated output into the rated load over the audio spec-
trum, and provides excellent linearity with an IMD (SMPTE)
typical rating of 0.004%.
Features
n 56W continuous average output power into 8
n 100W instantaneous peak output power capability
n Signal-to-Noise Ratio >95 dB (min)
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 |VEE| + |VCC| 12V, thus
eliminating turn-on and turn-off transients
n 11 lead TO-220 package
Applications
n Component stereo
n Compact stereo
n Self-powered speakers
n Surround-sound amplifiers
n High-end stereo TVs
Typical Application
DS011449-1
*Optional components dependent upon specific design requirements. Refer to the External Components Description section for a component function
description.
FIGURE 1. Typical Audio Amplifier Application Circuit
Overtureand SPiKeProtection are trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS011449
www.national.com
Page 1

Connection Diagram
Plastic Package (Note 8)
DS011449-2
Top View
Order Number LM3875T or LM3875TF
See NS Package Number TA11B for
Staggered Lead Non-Isolated Package
or TF11B for Staggered Lead Isolated Package
www.national.com
2
Page 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 |V+| + |V| (No Signal)
Supply Voltage |V+| + |V| (Input Signal)
Common Mode Input Voltage
Differential Input Voltage
Output Current
Power Dissipation (Note 3)
ESD Susceptibility (Note 4)
Junction Temperature (Note 5)
Soldering Information
T package (10 seconds)
94V
84V
(V+ or V) and
|V+| + |V| 80V
60V
Internally Limited
125W
2500V
150˚C
260˚C
Storage Temperature
Thermal Resistance
θJC
θJA
−40˚C to +150˚C
1˚C/W
43˚C/W
Operating Ratings (Notes 1, 2)
Temperature Range
TMIN TA TMAX
Supply Voltage |V+| + |V|
−20˚C TA +85˚C
20V to 84V
Note: Operation is guaranteed up to 84V, however, distortion may be intro-
duced from the SPiKe Protection Circuitry when operating above 70V if
proper thermal considerations are not taken into account. Refer to the Ther-
mal Considerations section for more information. (See SPiKe Protection Re-
sponse)
Electrical Characteristics (Notes 1, 2)
The following specifications apply for V+ = +35V, V= −35V with RL = 8unless otherwise specified. Limits apply for TA =
25˚C.
Symbol
Parameter
Conditions
|V+| + |V| Power Supply Voltage
**PO
Output Power (Continuous Average) THD + N = 0.1% (Max)
f = 1 kHz, f = 20 kHz
LM3875
Typical Limit
(Note 6) (Note 7)
20
84
Units
(Limits)
V (Min)
V (Max)
56 40 W (Min)
Peak PO
THD + N
**SR
*I+
Instantaneous Peak Output Power
Total Harmonic Distortion Plus Noise
Slew Rate (Note 9)
Total Quiescent Power Supply
Current
40W, 20 Hz f 20 kHz
AV = 26 dB
VIN = 1.414 Vrms, f = 10 kHz
Square-wave, RL = 2 k
VCM = 0V, VO = 0V, Io = 0 mA
100 W
0.06 %
11 5 V/µs
(Min)
30 70 mA
(Max)
*VOS
Input Offset Voltage
VCM = 0V, Io = 0 mA
1 10 mV
(Max)
IB Input Bias Current
VCM = 0V, Io = 0 mA
0.2 1
µA
(Max)
IOS
Io
*Vod
*PSRR
Input Offset Current
Output Current Limit
Output Dropout Voltage
Power Supply Rejection Ratio
*CMRR
*AVOL
GBWP
**eIN
Common Mode Rejection Ratio
Open Loop Voltage Gain
Gain-Bandwidth Product
Input Noise
VCM = 0V, Io = 0 mA
|V+| = |V| = 10V, ton = 10 ms, VO = 0V
|V+−Vo−|, V+ = 20V, Io = +100 mA
|Vo−V|, V= −20V, Io = −100 mA
V+ = 40V to 20V, V= −40V,
Vcm = 0V, Io = 0 mA
V+ = 40V, V = −40V to −20V,
Vcm = 0V, Io = 0 mA
V+ = 60V to 20V, V= −20V to −60V,
Vcm = 20V to −20V, Io = 0 mA
|V+| = |V| = 40V, RL = 2 k, VO = 60V
|V+| = |V| = 40V
fO = 100 kHz, VIN = 50 mVrms
IHF − A Weighting Filter
RIN = 600(Input Referred)
0.01
6
1.6
2.7
120
120
120
120
8
2.0
0.2 µA
(Max)
4 A(Min)
5 V (Max)
5 V (Max)
85
85
dB (Min)
80 dB (Min)
90 dB (Min)
2
MHz
(Min)
8.0
µV
(Max)
3 www.national.com
Page 3

Electrical Characteristics (Notes 1, 2) (Continued)
The following specifications apply for V+ = +35V, V= −35V with RL = 8unless otherwise specified. Limits apply for TA =
25˚C.
Symbol
Parameter
Conditions
LM3875
Typical Limit
(Note 6) (Note 7)
Units
(Limits)
SNR
Signal-to-Noise Ratio
IMD Intermodulation Distortion Test
PO = 1W, A-Weighted,
Measured at 1 kHz, RS =25
PO = 40W, A-Weighted,
Measured at 1 kHz, RS =25
Ppk = 100W, A-Weighted,
Measured at 1 kHz, RS =25
60 Hz, 7 kHz, 4:1 (SMPTE)
60 Hz, 7 kHz, 1:1 (SMPTE)
98 dB
114 dB
122 dB
0.004
0.006
dB
dB
dB
%
*DC Electrical Test; refer to Test Circuit #1.
**AC Electrical Test; refer to Test Circuit #2.
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is func-
tional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guar-
antee 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 2: All voltages are measured with respect to supply GND, unless otherwise specified.
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
θJC = 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 kresistor.
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 LM3875T package TA11B is a non-isolated package, setting the tab of the device and the heat sink at Vpotential when the LM3875 is directly mounted
to the heat sink using only thermal compound. If a mica washer is used in addition to thermal compound, θCS (case to sink) is increased, but the heat sink will be
isolated from V.
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/µs.
Note 10: 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)
www.national.com
DS011449-3
4
Page 4
Part Number LM3875
Manufactur National Semiconductor
Description LM3875 Overture Audio Power Amplifier Series High-Performance 56W Audio Power Amplifier
Total Page 19 Pages
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