- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄358867 > LM4889 (National Semiconductor Corporation) 1 Watt Audio Power Amplifier PDF資料下載
參數(shù)資料
| 型號(hào)： | LM4889 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 1 Watt Audio Power Amplifier |
| 中文描述： | 1瓦音頻功率放大器 |
| 文件頁(yè)數(shù)： | 10/19頁(yè) |
| 文件大小： | 763K |
| 代理商： | LM4889 |
第1頁(yè)第2頁(yè)第3頁(yè)第4頁(yè)第5頁(yè)第6頁(yè)第7頁(yè)第8頁(yè)第9頁(yè)當(dāng)前第10頁(yè)第11頁(yè)第12頁(yè)第13頁(yè)第14頁(yè)第15頁(yè)第16頁(yè)第17頁(yè)第18頁(yè)第19頁(yè)
Application Information
(Continued)
SELECTION OF INPUT CAPACITOR SIZE
Large input capacitors are both expensive and space hungry
for portable designs. Clearly, a certain sized capacitor is
needed to couple in low frequencies without severe attenu-
ation. But in many cases the speakers used in portable
systems, whether internal or external, have little ability to
reproduce signals below 100 Hz to 150 Hz. Thus, using a
large input capacitor may not increase actual system perfor-
mance.
In addition to system cost and size, click and pop perfor-
mance is effected by the size of the input coupling capacitor,
C
A larger input coupling capacitor requires more charge to
reach its quiescent DC voltage (nominally 1/2 V
). This
charge comes from the output via the feedback and is apt to
create pops upon device enable. Thus, by minimizing the
capacitor size based on necessary low frequency response,
turn-on pops can be minimized.
Besides minimizing the input capacitor size, careful consid-
eration should be paid to the bypass capacitor value. Bypass
capacitor, C
, is the most critical component to minimize
turn-on pops since it determines how fast the LM4889 turns
on. The slower the LM4889’s outputs ramp to their quiescent
DC voltage (nominally 1/2 V
DD
), the smaller the turn-on pop.
Choosing C
B
equal to 1.0 μF along with a small value of C
i
(in the range of 0.1 μF to 0.39 μF), should produce a virtually
clickless and popless shutdown function. While the device
will function properly, (no oscillations or motorboating), with
C
B
equal to 0.1 μF, the device will be much more susceptible
to turn-on clicks and pops. Thus, a value of C
B
equal to
1.0 μF is recommended in all but the most cost sensitive
designs.
AUDIO POWER AMPLIFIER DESIGN
A 1W/8
AUDIO AMPLIFIER
Given:
Power Output
Load Impedance
Input Level
Input Impedance
Bandwidth
1 Wrms
8
1 Vrms
20 k
100 Hz–20 kHz
±
0.25 dB
A designer must first determine the minimum supply rail to
obtain the specified output power. By extrapolating from the
Output Power vs Supply Voltage graphs in the
Typical Per-
formance Characteristics
section, the supply rail can be
easily found. A second way to determine the minimum sup-
ply rail is to calculate the required V
using Equation 2
and add the output voltage. Using this method, the minimum
supply voltage would be (V
+ (V
+ V
)), where
V
and V
are extrapolated from the Dropout Volt-
age vs Supply Voltage curve in the
Typical Performance
Characteristics
section.
(2)
5V is a standard voltage in most applications, it is chosen for
the supply rail. Extra supply voltage creates headroom that
allows the LM4889 to reproduce peaks in excess of 1W
without producing audible distortion. At this time, the de-
signer must make sure that the power supply choice along
with the output impedance does not violate the conditions
explained in the
Power Dissipation
section.
Once the power dissipation equations have been addressed,
the required differential gain can be determined from Equa-
tion 3.
(3)
R
f
/R
i
= A
VD
/2
From Equation 3, the minimum A
VD
is 2.83; use A
VD
= 3.
Since the desired input impedance was 20 k
, and with a
A
impedance of 2, a ratio of 1.5:1 of R
to R
results in an
allocation of R
i
= 20 k
and R
f
= 30 k
. The final design step
is to address the bandwidth requirements which must be
stated as a pair of 3 dB frequency points. Five times away
from a 3 dB point is 0.17 dB down from passband response
which is better than the required
±
0.25 dB specified.
f
L
= 100 Hz/5 = 20 Hz
f
H
= 20 kHz * 5 = 100 kHz
As stated in the
External Components
section, R
i
in con-
junction with C
i
create a highpass filter.
C
i
≥
1/(2
π
*20 k
*20 Hz) = 0.397 μF; use 0.39 μF
The high frequency pole is determined by the product of the
desired frequency pole, f
, and the differential gain, A
.
With a A
= 3 and f
= 100 kHz, the resulting GBWP =
300kHz which is much smaller than the LM4889 GBWP of
2.5MHz. This calculation shows that if a designer has a need
to design an amplifier with a higher differential gain, the
LM4889 can still be used without running into bandwidth
limitations.
L
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4890IBLX | GT 3C 3#16S SKT RECP WALL RM |
| LM4890ITLX | 1 Watt Audio Power Amplifier |
| LM4890LD | 1 Watt Audio Power Amplifier |
| LM4890MM | 1 Watt Audio Power Amplifier |
| LM4890M | 1 Watt Audio Power Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4889ITL | 功能描述:IC AMP AUDIO PWR 1W MONO 8USMD 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) |
| 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:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4889LD/NOPB | 功能描述:IC AMP AUDIO PWR 1W MONO 10LLP 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) |
| LM4889MA | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。