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参数资料
| 型号： | LM4681SQ |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and I2C/SPI Volume Control |
| 中文描述： | 10 W, 2 CHANNEL, AUDIO AMPLIFIER, PQCC48 |
| 封装： | LLP-48 |
| 文件页数： | 9/19页 |
| 文件大小： | 983K |
| 代理商： | LM4681SQ |
Application Hints
SUPPLY BYPASSING
Correct power supply bypassing has two important goals.
The first is to reduce noise on the power supply lines and
minimize deleterious effects that the noise may cause to the
amplifier’s operation. The second is to help stabilize an
unregulated power supply and to improve the supply’s tran-
sient response under heavy current demands. These two
goals require different capacitor value ranges. Therefore,
various types and values are recommended for supply by-
passing. For noise de-coupling, generally small ceramic ca-
pacitors (0.01F to 0.1F) are recommended. Larger value
(1F to 10F) tantalum capacitors are needed for the tran-
sient current demands. These two capacitors in parallel will
do an adequate job of removing most noise from the supply
rails and providing the necessary transient current. These
capacitors should be placed as close as possible to each
IC’s supply pin(s) using leads as short as possible.
The LM4681 has two different set of V
DD pins: a set for
power V
DD (PVDD) and a set for signal VDD (SVDD). The
parallel combination of the low value ceramic (0.1F) and
high value tantalum (10F) should be used to bypass the
PV
DD pin. A small value (0.1F) ceramic or tantalum can be
used to bypass the SV
DD pin.
OUTPUT STAGE FILTERING
The LM4681 requires a low pass filter connected between
the amplifier’s bridge output and the load. Figure 1 shows
the recommended LC filter. A minimum value of 27H is
recommended. As shown in Figure 1, using the values of the
components connected between the amplifier BTL outputs
and the load achieves a 2nd-order lowpass filter response
with a -3dB cutoff frequency of 25kHz.
THD+N MEASUREMENTS AND OUT OF AUDIO BAND
NOISE
THD+N (Total Harmonic Distortion plus Noise) is a very
important parameter by which all audio amplifiers are mea-
sured. Often it is shown as a graph where either the output
power or frequency is changed over the operating range. A
very important variable in the measurement of THD+N is the
bandwidth-limiting filter at the input of the test equipment.
Class D amplifiers, by design, switch their output power
devices at a much higher frequency than the accepted audio
range (20Hz - 20kHz). Alternately switching the output volt-
age between V
DD and GND allows the LM4681 to operate at
much higher efficiency than that achieved by traditional
Class AB amplifiers. Switching the outputs at high frequency
also increases the out-of-band noise. Under normal circum-
stances the output lowpass filter significantly reduces this
out-of-band noise. If the low pass filter is not optimized for a
given switching frequency, there can be significant increase
in out-of-band noise. THD+N measurements can be signifi-
cantly affected by out-of-band noise, resulting in a higher
than expected THD+N measurement. To achieve a more
accurate measurement of THD, the test equipment’s input
bandwidth of the must be limited. Some common upper filter
points are 22kHz, 30kHz, and 80kHz. The input filter limits
the noise component of the THD+N measurement to a
smaller bandwidth resulting in a more real-world THD+N
value.
LM4681
www.national.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4681SQ/NOPB | 功能描述:IC AMP AUDIO PWR 10W STER 48LLP 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) |
| LM4681SQX/NOPB | 功能描述:IC AMP AUDIO PWR 10W STER 48LLP 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) |
| LM4682 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and DC Volume Control |
| LM4682B E WAF | 制造商:Texas Instruments 功能描述: |
| LM4682SQ | 制造商:NSC 制造商全称:National Semiconductor 功能描述:10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and DC Volume Control |
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