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參數(shù)資料
| 型號： | LM4873MT |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Dual 2.1W Audio Amplifier Plus Stereo Headphone Function |
| 中文描述： | 1.9 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| 封裝： | 4.40 MM, PLASTIC, TSSOP-20 |
| 文件頁數(shù)： | 13/19頁 |
| 文件大小： | 532K |
| 代理商： | LM4873MT |
Application Information
(Continued)
CLICK AND POP CIRCUITRY
The LM4873 contains circuitry to minimize turn-on transients
or “clicks and pops”. In this case, turn-on refers to either
power supply turn-on or the device coming out of shutdown
mode. When the device is turning on, the amplifiers are inter-
nally configured as unity gain buffers. An internal current
source ramps up the voltage of the bypass pin. Both the in-
puts and outputs ideally track the voltage at the bypass pin.
The device will remain in buffer mode until the bypass pin
has reached its half supply voltage, 1/2 V
. As soon as the
bypass node is stable, the device will become fully opera-
tional, where the gain is set by the external resistors.
Although the bypass pin current source cannot be modified,
the size of C
can be changed to alter the device turn-on
time and the amount of “clicks and pops”. By increasing
amount of turn-on pop can be reduced. However, the
tradeoff for using a larger bypass capacitor is an increase in
turn-on time for this device. There is a linear relationship be-
tween the size of C
B
and the turn-on time. Here are some
typical turn-on times for a given C
B
:
C
B
0.01 μF
0.1 μF
0.22 μF
0.47 μF
1.0 μF
T
ON
20 ms
200 ms
420 ms
840 ms
2 Sec
In order eliminate “clicks and pops”, all capacitors must be
discharged before turn-on. Rapid on/off switching of the de-
vice or the shutdown function may cause the “click and pop”
circuitry to not operate fully, resulting in increased “click and
pop” noise. In a single-ended configuration, the output cou-
pling capacitor, C
, is of particular concern. This capacitor
discharges through the internal 20 k
resistors. Depending
on the size of C
, the time constant can be relatively large.
To reduce transients in single-ended mode, an external
1 k
–5 k
resistor can be placed in parallel with the internal
20 k
resistor. The tradeoff for using this resistor is an in-
crease in quiescent current.
The value of C
will also reflect turn-on pops. Clearly, a cer-
tain size for C
is needed to couple in low frequencies without
excessive attenuation. But in many cases, the speakers
used in portable systems, whether integral or external, have
little ability to reproduce signals below 100 Hz to 150 Hz. In
this case, using a large input and output capacitor may not
increase system performance. In most cases, choosing a
small value of C
in the range of 0.1 μF to 0.33 μF), along
with C
equal to 1.0 μF should produce a virtually clickless
and popless turn-on. In cases where C
is larger than
0.33 μF, it may be advantageous to increase the value of C
B
.
Again, it should be understood that increasing the value of
C
B
will reduce the “clicks and pops” at the expense of a
longer device turn-on time.
L
www.national.com
13
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4873MT/NOPB | 功能描述:IC AMP AUDIO PWR 3W STER 20TSSOP 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 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4873MTE | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM4873MTE/NOPB | 功能描述:音頻放大器 Dual 2.1W Audio Amp Plus Stereo HdPh Fcn RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4873MTE-1 | 功能描述:IC AMP AUDIO PWR 3W STER 28TSSOP 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 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4873MTE-1/NOPB | 制造商:Texas Instruments 功能描述:IC AMP AUDIO PWR 3W STER 28TSSOP |
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