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參數(shù)資料
| 型號： | LM4665LD/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, DSO10 |
| 封裝： | LLP-10 |
| 文件頁數(shù)： | 18/18頁 |
| 文件大?。?/td> | 1018K |
| 代理商： | LM4665LD/NOPB |
Typical Performance Characteristics (Continued)
Shutdown Hysteresis Voltage
V
DD = 3V, SD Mode = GND (SD High)
Supply Current
vs Supply Voltage
R
L =8
+ 33H
200270B0
20027002
Application Information
GENERAL AMPLIFIER FUNCTION
The output signals generated by the LM4665 consist of two,
BTL connected, output signals that pulse momentarily from
near ground potential to V
DD. The two outputs can pulse
independently with the exception that they both may never
pulse simultaneously as this would result in zero volts across
the BTL load. The minimum width of each pulse is approxi-
mately 160ns. However, pulses on the same output can
occur sequentially, in which case they are concatenated and
appear as a single wider pulse to achieve an effective 100%
duty cycle. This results in maximum audio output power for a
given supply voltage and load impedance. The LM4665 can
achieve much higher efficiencies than class AB amplifiers
while maintaining acceptable THD performance.
The short (160ns) drive pulses emitted at the LM4665 out-
puts means that good efficiency can be obtained with mini-
mal load inductance. The typical transducer load on an audio
amplifier is quite reactive (inductive). For this reason, the
load can act as it’s own filter, so to speak. This "filter-less"
switching amplifier/transducer load combination is much
more attractive economically due to savings in board space
and external component cost by eliminating the need for a
filter.
POWER DISSIPATION AND EFFICIENCY
In general terms, efficiency is considered to be the ratio of
useful work output divided by the total energy required to
produce it with the difference being the power dissipated,
typically, in the IC. The key here is “useful” work. For audio
systems, the energy delivered in the audible bands is con-
sidered useful including the distortion products of the input
signal.
Sub-sonic
(DC)
and
super-sonic
components
(>22kHz) are not useful. The difference between the power
flowing from the power supply and the audio band power
being transduced is dissipated in the LM4665 and in the
transducer load. The amount of power dissipation in the
LM4665 is very low. This is because the ON resistance of the
switches used to form the output waveforms is typically less
than 0.25
. This leaves only the transducer load as a po-
tential "sink" for the small excess of input power over audio
band output power. The LM4665 dissipates only a fraction of
the excess power requiring no additional PCB area or cop-
per plane to act as a heat sink.
DIFFERENTIAL AMPLIFIER EXPLANATION
As logic supply voltages continue to shrink, designers are
increasingly turning to differential analog signal handling to
preserve signal to noise ratios with restricted voltage swing.
The LM4665 is a fully differential amplifier that features
differential input and output stages. A differential amplifier
amplifies the difference between the two input signals. Tra-
ditional audio power amplifiers have typically offered only
single-ended inputs resulting in a 6dB reduction in signal to
noise ratio relative to differential inputs. The LM4665 also
offers the possibility of DC input coupling which eliminates
the two external AC coupling, DC blocking capacitors. The
LM4665 can be used, however, as a single ended input
amplifier while still retaining it’s fully differential benefits. In
fact, completely unrelated signals may be placed on the
input pins. The LM4665 simply amplifies the difference be-
tween the signals. A major benefit of a differential amplifier is
the improved common mode rejection ratio (CMRR) over
single input amplifiers. The common-mode rejection charac-
teristic of the differential amplifier reduces sensitivity to
ground offset related noise injection, especially important in
high noise applications.
PCB LAYOUT CONSIDERATIONS
As output power increases, interconnect resistance (PCB
traces and wires) between the amplifier, load and power
supply create a voltage drop. The voltage loss on the traces
between the LM4665 and the load results is lower output
power and decreased efficiency. Higher trace resistance
between the supply and the LM4665 has the same effect as
a poorly regulated supply, increase ripple on the supply line
also reducing the peak output power. The effects of residual
trace resistance increases as output current increases due
to higher output power, decreased load impedance or both.
To maintain the highest output voltage swing and corre-
sponding peak output power, the PCB traces that connect
LM4665
www.national.com
9
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4665LDX | 制造商:ROCHESTER 制造商全稱:ROCHESTER 功能描述:NATIONALa??S AUDIO AMPLIFIER now featuring RoHS compliancy Audio Amplifier |
| LM4665LDX-G | 制造商:Rochester Electronics LLC 功能描述: |
| LM4665MM | 制造商:Texas Instruments 功能描述:AMP AUDIO 1W SWITCH SMD MSOP10 |
| LM4665MM/NOPB | 功能描述:IC AMP AUDIO 1.4W MONO AB 10MSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機，2-通道（立體聲） 在某負載時最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點:I²C，麥克風，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4665MMX | 制造商:ROCHESTER 制造商全稱:ROCHESTER 功能描述:NATIONALa??S AUDIO AMPLIFIER now featuring RoHS compliancy Audio Amplifier |
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