|
|
PDF LM4731 Data sheet ( Hoja de datos )
| Número de pieza | LM4731 | |
| Descripción | Stereo 25W Audio Power Amplifier with Mute and Standby Modes | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LM4731 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
July 2003
LM4731
Stereo 25W Audio Power Amplifier with Mute and
Standby Modes
General Description
The LM4731 is a stereo audio amplifier capable of delivering
typically 25W per channel of continuous average output
power into a 4Ω or 8Ω load with less than 10% THD+N from
20Hz - 20kHz.
Each amplifier has an independent smooth transition fade-
in/out mute and a power conserving standby mode which
can be controlled by external logic.
The LM4731 has short circuit protection and a thermal shut
down feature that is activated when the die temperature
exceeds 150˚C. The LM4731 also has a under voltage lock
out feature for click and pop free power off and on.
The LM4731 has a wide operating supply range from +/-10V
- +/-28V allowing for lower cost unregulated power supplies
to be used.
Key Specifications
j Output Power into 4Ω or 8Ω, 10% THD+N 25W (typ)
j THD+N at 1kHz with 2 x 1W into 8Ω
0.02% (typ)
j Mute Attenuation
85dB (typ)
j PSRR with fRIPPLE = 120Hz,
VRIPPLE = 1VRMS
j Slew Rate
50dB (typ)
18V/µs (typ)
j Standby Current (+/-22V)
4.8mA (typ)
Features
n Minimal amount of external components necessary
n Quiet fade-in/out mute mode
n Low current Standby-mode
Applications
n Audio amplifier for high-end stereo TVs
n Audio amplifier for component stereo
n Audio amplifier for compact stereo
n Audio amplifier for PC satellite speaker systems
n Audio amplifier for self powered speakers
Connection Diagrams
Plastic Package
TO-220 Top Marking (Note 12)
Top View
Non-Isolated Package
Order Number LM4731TA
See NS Package Number TA15A
20060352
© 2003 National Semiconductor Corporation DS200603
20060375
Top View
U - Wafer Fab Code
Z - Assembly Plant Code
XY - Date Code
TT - Die Traceability
LM4731TA - LM4731TA
www.national.com
1 page  
Single Supply Application Circuit
FIGURE 3. Single Supply Amplifier Application Circuit
Note: *Optional components dependent upon specific design requirements.
Auxiliary Amplifier Application Circuit
20060306
20060307
FIGURE 4. Special Audio Amplifier Application Circuit
5 www.national.com
5 Page 
Application Information (Continued)
These instabilities can be eliminated through multiple by-
passing utilizing a large tantalum or electrolytic capacitor (10
µF or larger) which is used to absorb low frequency varia-
tions and a small ceramic capacitor (0.1 µF) to prevent any
high frequency feedback through the power supply lines.
If adequate bypassing is not provided, the current in the
supply leads which is a rectified component of the load
current may be fed back into internal circuitry. This signal
causes distortion at high frequencies requiring that the sup-
plies be bypassed at the package terminals with an electro-
lytic capacitor of 470 µF or more.
BRIDGED AMPLIFIER APPLICATION
The LM4731 has two operational amplifiers internally, allow-
ing for a few different amplifier configurations. One of these
configurations is referred to as “bridged mode” and involves
driving the load differentially through the LM4731’s outputs.
This configuration is shown in Figure 2. Bridged mode op-
eration is different from the classical single-ended amplifier
configuration where one side of its load is connected to
ground.
A bridge amplifier design has a distinct advantage over the
single-ended configuration, as it provides differential drive to
the load, thus doubling output swing for a specified supply
voltage. Consequently, theoretically four times the output
power is possible as compared to a single-ended amplifier
under the same conditions. This increase in attainable output
power assumes that the amplifier is not current limited or
clipped.
A direct consequence of the increased power delivered to
the load by a bridge amplifier is an increase in internal power
dissipation. For each operational amplifier in a bridge con-
figuration, the internal power dissipation will increase by a
factor of two over the single ended dissipation. Thus, for an
audio power amplifier such as the LM4731, which has two
operational amplifiers in one package, the package dissipa-
tion will increase by a factor of four. To calculate the
LM4731’s maximum power dissipation point for a bridged
load, multiply equation (1) by a factor of four.
This value of PDMAX can be used to calculate the correct size
heat sink for a bridged amplifier application. Since the inter-
nal dissipation for a given power supply and load is in-
creased by using bridged-mode, the heatsink’s θSA will have
to decrease accordingly as shown by equation (3). Refer to
the section, Determining the Correct Heat Sink, for a more
detailed discussion of proper heat sinking for a given appli-
cation.
SINGLE-SUPPLY AMPLIFIER APPLICATION
The typical application of the LM4731 is a split supply am-
plifier. But as shown in Figure 3, the LM4731 can also be
used in a single power supply configuration. This involves
using some external components to create a half-supply bias
which is used as the reference for the inputs and outputs.
Thus, the signal will swing around half-supply much like it
swings around ground in a split-supply application. Along
with proper circuit biasing, a few other considerations must
be accounted for to take advantage of all of the LM4731
functions.
The LM4731 possesses a mute and standby function with
internal logic gates that are half-supply referenced. Thus, to
enable either the Mute or Standby function, the voltage at
these pins must be a minimum of 2.5V above half-supply. In
single-supply systems, devices such as microprocessors
and simple logic circuits used to control the mute and
standby functions, are usually referenced to ground, not
half-supply. Thus, to use these devices to control the logic
circuitry of the LM4731, a “level shifter,” like the one shown in
Figure 5, must be employed. A level shifter is not needed in
a split-supply configuration since ground is also half-supply.
20060354
FIGURE 5. Level Shift Circuit
When the voltage at the Logic Input node is 0V, the 2N3904
is “off” and thus resistor Rc pulls up mute or standby input to
the supply. This enables the mute or standby function. When
the Logic Input is 5V, the 2N3904 is “on” and consequently,
the voltage at the collector is essentially 0V. This will disable
the mute or standby function, and thus the amplifier will be in
its normal mode of operation. Rshift, along with Cshift, creates
an RC time constant that reduces transients when the mute
or standby functions are enabled or disabled. Additionally,
Rshift limits the current supplied by the internal logic gates of
the LM4731 which insures device reliability. Refer to the
Mute Mode and Standby Mode sections in the Application
Information section for a more detailed description of these
functions.
CLICKS AND POPS
In the typical application of the LM4731 as a split-supply
audio power amplifier, the IC exhibits excellent “click” and
“pop” performance when utilizing the mute and standby
modes. In addition, the device employs Under-Voltage Pro-
tection, which eliminates unwanted power-up and power-
down transients. The basis for these functions are a stable
and constant half-supply potential. In a split-supply applica-
tion, ground is the stable half-supply potential. But in a
single-supply application, the half-supply needs to charge up
just like the supply rail, VCC. This makes the task of attaining
a clickless and popless turn-on more challenging. Any un-
even charging of the amplifier inputs will result in output
clicks and pops due to the differential input topology of the
LM4731.
11 www.national.com
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LM4731.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LM4730 | LM4730 Stereo 14W Audio Power Amplifier with Mute and Standby Modes (Rev. C) |  Texas Instruments |
| LM4730 | Stereo 14W Audio Power Amplifier | National Semiconductor |
| LM4731 | Stereo 25W Audio Power Amplifier with Mute and Standby Modes | National Semiconductor |
| LM4731 | LM4731 Stereo 25W Audio Power Amplifier with Mute and Standby Modes (Rev. C) | Texas Instruments |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |