- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄30753 > LM4850LDX/NOPB (NATIONAL SEMICONDUCTOR CORP) 0.3 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO14 PDF資料下載
參數(shù)資料
| 型號(hào)： | LM4850LDX/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 0.3 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO14 |
| 封裝： | 0.118 INCH, 0.80 MM PITCH, LLP-14 |
| 文件頁數(shù)： | 5/20頁 |
| 文件大?。?/td> | 1112K |
| 代理商： | LM4850LDX/NOPB |
Application Information (Continued)
Also shown in Figure 2 are the electrical connections for the
headphone jack and plug. A 3-wire plug consists of a Tip,
Ring, and Sleave, where the Tip and Ring are audio signal
conductors and the Sleave is the common ground return.
One control pin for each headphone jack is sufficient to
indicate to the control inputs that a user has inserted a plug
into the jack and that the headphone mode of operation is
desired.
To ensure smooth transition from BTL to SE operation, it is
important to connect HP-IN and R
PU1 to the control pin on
the Right Output of the headphone jack. The control pin on
the Left Output of the headphone jack should be left open.
Connecting the node between the HP-IN and R
PU1 to the
Left Output control pin may cause unwanted state changes
to the HP-IN pin.
PROPER SELECTION OF EXTERNAL COMPONENTS
Proper selection of external components in applications us-
ing integrated power amplifiers is critical for optimum device
and system performance. While the LM4850 is tolerant to a
variety of external component combinations, consideration
must be given to the external component values that maxi-
mize overall system quality.
The LM4850’s unity-gain stability allows a designer to maxi-
mize system performance. The LM4850’s gain should be set
no higher than necessary for any given application. A low
gain configuration maximizes signal-to-noise performance
and minimizes THD+N. However, a low gain configuration
also requires large input signals to obtain a given output
power. Input signals equal to or greater than 1V
RMS are
available from sources such as audio codecs. Please refer to
the section, Audio Power Amplifier Design, for a more
complete explanation of proper gain selection.
Selecting Input and Output Capacitor Values
Besides gain, one of the major considerations is the
closed-loop bandwidth of the amplifier. To a large extent, the
bandwidth is dictated by the choice of external components
shown in Figure 1. The input coupling capacitor C
I and
resistor R
I form a first order high pass filter that limits low
frequency response. C
I’s value should be based on the
desired frequency response weighed against the following:
Large value input and output capacitors are both expensive
and space consuming for portable designs. Clearly a certain
sized capacitor is needed to couple in low frequencies with-
out severe attenuation. But in many cases the speakers
used in portable systems, whether internal or external, have
little ability to reproduce signals below 150Hz. Thus, large
value input and output capacitors may not increase system
performance.
AUDIO POWER AMPLIFIER DESIGN
Design a 1W / 8
Bridged Audio Amplifier
Given:
Power Output:
1W
RMS
Load Impedance
8
Input Level:
1V
RMS
Input Impedance:
20k
Bandwidth:
100Hz - 20kHz ± 0.25dB
A designer must first determine the minimum supply voltage
needed to obtain the specified output power. By extrapolat-
ing from the Output Power vs Supply Voltage graphs in the
Typical Performance Characteristics section, the supply
rail can be easily found. A second way to determine the
minimum supply rail is to calculate the required V
OPEAK
using Equation 5 and add the dropout voltage. This results in
Equation 6, where V
ODTOP and VODBOT are extrapolated
from the Dropout Voltage vs Supply Voltage curve in the
Typical Performance Characteristics section.
(5)
V
DD
≥ (V
OPEAK +(VODTOP +VODBOT))
(6)
Using the Output Power vs Supply Voltage graph for an 8
load, the minimum supply rail is 4.7V. But since 5V is a
standard supply voltage in most applications, it is chosen for
the supply rail. Extra supply voltage creates headroom that
allows the LM4850 to reproduce peaks in excess of 1W
without producing audible distortion. However, the designer
must make sure that the chosen power supply voltage and
output load 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 7.
(7)
R
F /RI =AVD / 2
(8)
From Equation 6, the minimum A
VD is 2.83; use AVD =3.
The desired input impedance was 20k
, and with an A
VD of
3, using Equation 8 results in an allocation of R
I = 20k
and
R
F = 30k
.
The final design step is to set the amplifier’s 3dB frequency
bandwidth. To achieve the desired ± 0.25dB pass band
magnitude variation limit, the low frequency response must
20001050
FIGURE 2. Headphone Control Circuit
LM4850
www.national.com
13
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4850MMX/NOPB | 0.3 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO10 |
| LM4850MTX/NOPB | 0.3 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO14 |
| LM4851ITL/NOPB | 1.1 W, 3 CHANNEL, AUDIO AMPLIFIER, PBGA18 |
| LM4851LQ/NOPB | 1.5 W, 3 CHANNEL, AUDIO AMPLIFIER, QCC24 |
| LM4852LQ/NOPB | 1.5 W, 3 CHANNEL, AUDIO AMPLIFIER, QCC24 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4850MM | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Mono 1.5 W / Stereo 300 mW Power Amplifier |
| LM4850MM/NOPB | 功能描述:IC AMP AUDIO PWR 1.9W AB 10MSOP 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) |
| LM4850MMX | 功能描述:IC AMP AUDIO PWR 1.9W AB 10MSOP 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) |
| LM4850MMX/NOPB | 制造商:Texas Instruments 功能描述:Audio Amp Headphone/Speaker 1-CH Mono/2-CH Stereo 1.5W Class-AB 10-Pin MSOP T/R |
| LM4850MT | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Mono 1.5 W / Stereo 300 mW Power Amplifier |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。