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參數(shù)資料
| 型號(hào)： | LM4863MT/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| 封裝： | 4.40 MM, TSSOP-20 |
| 文件頁(yè)數(shù)： | 7/21頁(yè) |
| 文件大?。?/td> | 1165K |
| 代理商： | LM4863MT/NOPB |
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Application Information (Continued)
sents a tradeoff: as the size of C
B increases, the turn-on time
increases. There is a linear relationship between the size of
C
B and the turn-on time. Here are some typical turn-on times
for various values of C
B:
C
B
T
ON
0.01F
20 ms
0.1F
200 ms
0.22F
440 ms
0.47F
940 ms
1.0F
2 Sec
In order eliminate "clicks and pops", all capacitors must be
discharged before turn-on. Rapidly switching V
DD may not
allow the capacitors to fully discharge, which may cause
"clicks and pops". In a single-ended configuration, the output
is coupled to the load by C
OUT. This capacitor usually has a
high value. C
OUT discharges through internal 20k
resistors.
Depending on the size of C
OUT, the discharge time constant
can be relatively large. To reduce transients in single-ended
mode, an external 1k
-5k resistor can be placed in
parallel with the internal 20k
resistor. The tradeoff for using
this resistor is increased quiescent current.
NO LOAD STABILITY
The LM4863 may exhibit low level oscillation when the load
resistance is greater than 10k
. This oscillation only occurs
as the output signal swings near the supply voltages. Pre-
vent this oscillation by connecting a 5k
between the output
pins and ground.
AUDIO POWER AMPLIFIER DESIGN
Audio Amplifier Design: Driving 1W into an 8
Load
The following are the desired operational parameters:
Power Output:
1Wrms
Load Impedance:
8
Input Level:
1Vrms
Input Impedance:
20k
Bandwidth:
100Hz20 kHz 0.25 dB
The design begins by specifying the minimum supply voltage
necessary to obtain the specified output power. One way to
find the minimum supply voltage is to use the Output Power
vs Supply Voltage curve in the Typical Performance Char-
acteristics section. Another way, using Equation (4), is to
calculate the peak output voltage necessary to achieve the
desired output power for a given load impedance. To ac-
count for the amplifier’s dropout voltage, two additional volt-
ages, based on the Dropout Voltage vs Supply Voltage in the
Typical Performance Characteristics curves, must be
added to the result obtained by Equation (8). The result in
Equation (9).
(8)
V
DD
≥ (V
OUTPEAK +(VODTOP +VODBOT))
(9)
The Output Power vs Supply Voltage graph for an 8
load
indicates a minimum supply voltage of 4.6V. This is easily
met by the commonly used 5V supply voltage. The additional
voltage creates the benefit of headroom, allowing the
LM4863 to produce peak output power in excess of 1W
without clipping or other audible distortion. The choice of
supply voltage must also not create a situation that violates
maximum power dissipation as explained above in the
Power Dissipation section.
After satisfying the LM4863’s power dissipation require-
ments, the minimum differential gain is found using Equation
(10).
(10)
Thus, a minimum gain of 2.83 allows the LM4863’s to reach
full output swing and maintain low noise and THD+N perfor-
mance. For this example, let A
VD =3.
The amplifier’s overall gain is set using the input (R
i) and
feedback (R
f) resistors. With the desired input impedance
set at 20k
, the feedback resistor is found using Equation
(11).
R
f/Ri =AVD/2
(11)
The value of R
f is 30k
.
The last step in this design example is setting the amplifier’s
3dB frequency bandwidth. To achieve the desired ±0.25dB
pass band magnitude variation limit, the low frequency re-
sponse must extend to at least onefifth the lower bandwidth
limit and the high frequency response must extend to at least
five times the upper bandwidth limit. The gain variation for
both response limits is 0.17dB, well within the ±0.25dB
desired limit. The results are an
f
L = 100Hz/5 = 20Hz
(12)
and an
F
H = 20kHzx5 = 100kHz
(13)
As mentioned in the External Components section, R
i
and C
i create a highpass filter that sets the amplifier’s lower
bandpass frequency limit. Find the coupling capacitor’s
value using Equation (12).
the result is
1/(2
π*20k*20Hz) = 0.398F
(14)
Use a 0.39F capacitor, the closest standard value.
The product of the desired high frequency cutoff (100kHz in
this example) and the differential gain, A
VD, determines the
upper passband response limit. With A
VD = 3 and fH =
100kHz, the closed-loop gain bandwidth product (GBWP) is
300kHz. This is less than the LM4863’s 3.5MHz GBWP. With
this margin, the amplifier can be used in designs that require
more differential gain while avoiding performance-lrestricting
bandwidth limitations.
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figures 3 through 6 show the recommended two-layer PC
board layout that is optimized for the 20-pin MTE-packaged
LM4863 and associated external components. Figures 7
through 11 show the recommended four-layer PC board
layout that is optimized for the 24-pin LQ-packaged LM4863
and associated external components. These circuits are de-
signed for use with an external 5V supply and 4
speakers.
These circuit boards are easy to use. Apply 5V and ground to
the board’s V
DD and GND pads, respectively. Connect 4
speakers between the board’s -OUTA and +OUTA and
OUTB and +OUTB pads.
LM4863
www.national.com
15
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| LM4863MX/NOPB | 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO16 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4863MTX/NOPB | 功能描述:IC AMP AUDIO PWR 3.2W AB 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(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)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(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，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) |
| LM4863MX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Engineering Project Manager |
| LM4863MX/NOPB | 功能描述:IC AMP AUDIO PWR 3.2W AB 16SOIC RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)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(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，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) |
| LM4863N | 功能描述:IC AMP AUDIO PWR 3.2W STER 16DIP RoHS:否 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)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(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，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) |
| LM4864 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:300 mW Audio Power Amplifier with Shutdown Mode |
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