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參數(shù)資料
| 型號： | LM4888 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Dual 2.1W Audio Amplifier Plus Stereo Headphone & 3D Enhancement |
| 中文描述： | 雙2.1W音頻功率放大器加立體聲耳機 |
| 文件頁數(shù)： | 18/22頁 |
| 文件大?。?/td> | 1179K |
| 代理商： | LM4888 |
Application Information
(Continued)
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 one-fifth 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
and an
f
H
= 20kHz*5 = 100kHz.
As mentioned in the
External Components
section, R
and
C
create a highpass filter that sets the amplifier’s lower
bandpass frequency limit. Find the coupling capacitor’s
value using Equation (12).
C
1
≥
1/(2
π
R
1
f
L
)
The result is
1/(2
π
*20k
*20Hz) = 0.398μF.
Use a 0.39μF capacitor, the closest standard value.
The product of the desired high frequency cutoff (100kHz in
this example) and the differential gain, AVD, determines the
upper passband response limit. With A
VD
= 3 and f
H
=
100kHz, the closed-loop gain bandwidth product (GBWP) is
300kHz. This is less than the LM4888’s 3.5MHz GBWP. With
this margin, the amplifier can be used in designs that require
more differential gain while avoiding performance-restricting
bandwidth limitations.
(12)
NATIONAL 3D ENHANCEMENT
The LM4888 features a 3D audio enhancement effect that
widens the perceived soundstage from a stereo audio signal.
The 3D audio enhancement improves the apparent stereo
channel separation whenever the left and right speakers are
too close to one another, due to system size constraints or
equipment limitations.
An external RC network, Shown in figure 1, is required to
enable the 3D effect. The amount of the 3D effect is set by
the R5 and C7 or C3D ADJ. Decreasing the value of R5 will
increase the 3D effect. Increasing the value of the capacitors
(C7 or C3D) will decrease the low cutoff frequency at which
the 3D effect starts to occur., as shown by Equation 13.
F
3D(–3dB)
= 1 / 2
π
(R
3D
)(C
3D
)
Activating the 3D effect will cause an increase in gain by a
multiplication factor of (1 + 20k
/R5). Setting R5 to 20k
will
result in a gain increase by a multiplication factor of (1 +
20k
/20k
) = 2 or 6dB whenever the 3D effect is activated.
The amount of perceived 3D is also dependent on many
other factors such as speaker placement and the distance to
the listener. Therefore, it is recommended that the user try
various values of R5 and C3D to get a feel for how the 3D
effect works in the application. There is not a “right or wrong”
for the effect, it is merely what is most pleasing to the
individual user. Take note that R3 and R4 replace R2, and
R7 and R6 replace R8 when 3D mode is enabled.
(13)
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figures 3 through 6 show the recommended two-layer PC
board layout that is optimized for the 24-pin SQ package.
These circuits are designed for use with an external 5V
supply and 8
, 4
, 3
speakers.
These circuit boards are easy to use. Apply power and
ground to the board’s V
and GND pads, respectively.
Connect the speakers between the board’s OUTA and
+OUTA and OUTB and +OUTB pads.
L
www.national.com
18
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4888_06 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual 2.1W Audio Amplifier Plus Stereo Headphone & 3D Enhancement |
| LM4888A E WAF | 制造商:Texas Instruments 功能描述: |
| LM4888SQ | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual 2.1W Audio Amplifier Plus Stereo Headphone & 3D Enhancement |
| LM4888SQ/NOPB | 功能描述:IC AMP AUDIO PWR 3W STER 24LLP 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(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4888SQBD | 功能描述:BOARD EVALUATION LM4888SQ RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 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:1 系列:- |
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