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PDF LM3876 Data sheet ( Hoja de datos )
| Número de pieza | LM3876 | |
| Descripción | LM3876 Overture Audio Power Amplifier Series High-Performance 56W Audio Power Amplifier w/Mute | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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April 1995
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 8Ω load with 0.1% (THD + N) from 20 Hz–20 kHz.
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 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 8Ω
n 100W instantaneous peak output power capability
n Signal-to-Noise Ratio ≥ 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 |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
Overture™ and SPiKe™ Protection are trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS011832
www.national.com
1 page  
Test Circuit #2 (AC Electrical Test Circuit)
Single Supply Application Circuit
DS011832-4
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 www.national.com
5 Page 
Typical Performance Characteristics (Continued)
Mute Attenuation vs
Mute Current
Mute Attenuation vs
Mute Current
Large Signal Response
Power Supply
Rejection Ratio
DS011832-44
Common-Mode
Rejection Ratio
DS011832-45
DS011832-46
Open Loop
Frequency Response
DS011832-47
Application Information
GENERAL FEATURES
Mute Function: The muting function of the LM3876 allows
the user to mute the music going into the amplifier by draw-
ing less than 0.5 mA out of pin 8 of the device. This is accom-
plished as shown in the Typical Application Circuit where the
resistor RM is chosen with reference to your negative supply
voltage and is used in conjuction with a switch. The switch
(when opened) cuts off the current flow from pin 8 to V−, thus
placing the LM3876 into mute mode. Refer to the Mute At-
tenuation vs Mute Current curves in the Typical Perfor-
mance Characteristics section for values of attenuation per
current out of pin 8. The resistance RM is calculated by the
following equation:
RM (|VEE| − 2.6V)/I8 where I8 ≥ 0.5 mA.
Under-Voltage Protection: Upon system power-up the
under-voltage protection circuitry allows the power supplies
and their corresponding caps to come up close to their full
values before turning on the LM3876 such that no DC output
spikes occur. Upon turn-off, the output of the LM3876 is
brought to ground before the power supplies such that no
transients occur at power-down.
Over-Voltage Protection: The LM3876 contains overvolt-
age protection circuitry that limits the output current to ap-
proximately 6Apeak while also providing voltage clamping,
though not through internal clamping diodes. The clamping
effect is quite the same, however, the output transistors are
designed to work alternately by sinking large current spikes.
DS011832-48
DS011832-49
SPiKe Protection: The LM3876 is protected from instanta-
neous peak-temperature stressing by the power transistor
array. The Safe Operating Area graph in the Typical Perfor-
mance Characteristics section shows the area of device
operation where the SPiKe Protection Circuitry is not en-
abled. The waveform to the right of the SOA graph exempli-
fies how the dynamic protection will cause waveform distor-
tion when enabled.
Thermal Protection: The LM3876 has a sophisticated ther-
mal protection scheme to prevent long-term thermal stress
to the device. When the temperature on the die reaches
165˚C, the LM3876 shuts down. It starts operating again
when the die temperature drops to about 155˚C, but if the
temperature again begins to rise, shutdown will occur again
at 165˚C. Therefore the device is allowed to heat up to a
relatively high temperature if the fault condition is temporary,
but a sustained fault will cause the device to cycle in a
Schmitt Trigger fashion between the thermal shutdown tem-
perature limits of 165˚C and 155˚C. This greatly reduces the
stress imposed on the IC by thermal cycling, which in turn
improves its reliability under sustained fault conditions.
Since the die temperature is directly dependent upon the
heat sink, the heat sink should be chosen as discussed in
the Thermal Considerations section, such that thermal
shutdown will not be reached during normal operation. Using
the best heat sink possible within the cost and space con-
straints of the system will improve the long-term reliability of
any power semiconductor device.
11 www.national.com
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet LM3876.PDF ] | |
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