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參數(shù)資料
| 型號： | LM4668LDX/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 10 W, 1 CHANNEL, AUDIO AMPLIFIER, DSO14 |
| 文件頁數(shù)： | 14/14頁 |
| 文件大?。?/td> | 472K |
| 代理商： | LM4668LDX/NOPB |
Application Hints (Continued)
nominal cutoff frequency of 47kHz. This cutoff frequency
ensures that the attenuation is much less than 3dB at 20kHz.
The output filter cutoff frequency and topology are also
optimized for operational efficiency. A higher cutoff frequency
compromises efficiency, whereas a lower cutoff frequency
compromises the high frequencies within the audio fre-
quency range. The filter’s topology also minimizes high fre-
quency peaking, which can also decrease the amplifier’s
efficiency.
The output filter inductors must have a current rating that
exceeds the amplifier’s output current when driving the load
to maximum dissipation. Assuming a load dissipation of 10W
in an 8
load with the amplifier operating on a 14V supply,
the RMS current is 1.1A. In this case, the inductors’ current
rating should be at least 1.2A
RMS or 1.6APEAK.
If a different output filter cutoff frequency (f
C) is desired, the
following brief discussion covers the selection of the capaci-
tor and inductor values. In the following equations, R
L is the
load resistance and C
L is three times the final value of the
three common-mode filter capacitor found between the two
output filter inductors (each inductor is L) as shown in Figure
1. When calculating values for L and C
L,RL should be 8
,
since the LM4668 is specified for 8
loads.
The filter’s two inductors are equal to
L= R
L /2
πf
C
(1)
and each of the three capacitors are equal to
C = L / 1.5R
2
(2)
SCHOTTKY DIODE AMPLIFIER OUTPUT OVERDRIVE
PROTECTION
The Schottky diodes shown in Figure 1 provide protection
against an over-voltage condition that may be caused by
inductor-induced transients. These diodes are necessary
when the nominal supply voltage exceeds 12V, the load
impedance falls below 6
or the ambient temperature in the
operating environment rises above 50C.
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 LM4668 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.
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figures 2 through 4 show the recommended two-layer PC
board layout that is optimized for the 14-pin MH-packaged
LM4668 and associated external components. Figures 5
through 7 show the recommended two-layer PC board lay-
out that is optimized for the 14-pin LD-packaged LM4668
and associated external components. These circuits are de-
signed for use with an external 12V supply and 8
speakers
(or load resistors). This circuit board is easy to use. Apply
12V and ground to the board’s V
DD and GND terminals,
respectively. Connect speakers (or load resistors) between
the board’s -OUT and +OUT terminals. Apply the input signal
to the input pin labeled -IN.
LM4668
www.national.com
9
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4668MH | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:10W High-Efficiency Mono BTL Audio Power Amplifier |
| LM4668MH/NOPB | 功能描述:IC AMP AUDIO 10W MONO D 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) |
| LM4668MHX/NOPB | 功能描述:IC AMP AUDIO 10W MONO D 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) |
| LM4670 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Filterless High Efficiency 3W Switching Audio Amplifier |
| LM4670_06 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Filterless High Efficiency 3W Switching Audio Amplifier |
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