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参数资料
| 型号： | LM4888SQ/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 3 W, 2 CHANNEL, AUDIO AMPLIFIER, QCC24 |
| 封装： | LLP-24 |
| 文件页数： | 10/23页 |
| 文件大小： | 1181K |
| 代理商： | LM4888SQ/NOPB |
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
1 and
C
1 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/(2πR
1fL)
(12)
The result is
1/(2
π*20k*20Hz) = 0.398F.
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, AVD, 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 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.
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)(C3D)
(13)
Activating the 3D effect by applying V
DD to pin 9 (3D Control)
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)=2or6dB
whenever the 3D effect is activated. The amount of per-
ceived 3D is also dependent on many other factors such as
speaker placement and the distance to the listener. There-
fore, 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.
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
DD and GND pads, respectively.
Connect the speakers between the board’s OUTA and
+OUTA and OUTB and +OUTB pads.
LM4888
www.national.com
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4888SQX/NOPB | 功能描述:IC AMP AUDIO PWR 3W STER 24LLP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4889 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1 Watt Audio Power Amplifier |
| LM4889ITL | 功能描述:IC AMP AUDIO PWR 1W MONO 8USMD RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4889ITLX | 制造商:Texas Instruments 功能描述:Audio Amp Speaker 1-CH Mono 1W Class-AB 8-Pin uSMD T/R |
| LM4889ITLX/NOPB | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
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