- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄30752 > LM4816MT/NOPB (NATIONAL SEMICONDUCTOR CORP) 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 PDF資料下載
參數(shù)資料
| 型號(hào)： | LM4816MT/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| 封裝： | 4.40 MM, TSSOP-20 |
| 文件頁數(shù)： | 2/13頁 |
| 文件大?。?/td> | 432K |
| 代理商： | LM4816MT/NOPB |
Application Information (Continued)
presence does not eliminate the need for a local 1.0F
tantalum bypass capacitance connected between the
LM4816’s supply pins and ground. Do not substitute a ce-
ramic capacitor for the tantalum. Doing so may cause oscil-
lation in the output signal. Keep the length of leads and
traces that connect capacitors between the LM4816’s power
supply pin and ground as short as possible. Connecting a
1F capacitor, C
B, between the BYPASS pin and ground
improves the internal bias voltage’s stability and improves
the amplifier’s PSRR. The PSRR improvements increase as
the bypass pin capacitor value increases. Too large, how-
ever, increases turn-on time and can compromise amplifier’s
click and pop performance. The selection of bypass capaci-
tor values, especially C
B, depends on desired PSRR require-
ments, click and pop performance (as explained in the sec-
tion, Proper Selection of External Components), system
cost, and size constraints.
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the
LM4816’s shutdown function. Activate micro-power shut-
down by applying V
DD to the SHUTDOWN pin. When active,
the LM4816’s micro-power shutdown feature turns off the
amplifier’s bias circuitry, reducing the supply current. The
logic threshold is typically V
DD/2. The low 0.6A typical
shutdown current is achieved by applying a voltage that is as
near as V
DD as possible to the SHUTDOWN pin. A voltage
thrat is less than V
DD may increase the shutdown current.
There are a few ways to control the micro-power shutdown.
These include using a single-pole, single-throw switch, a
microprocessor, or a microcontroller. When using a switch,
connect an external 10k
pull-up resistor between the
SHUTDOWN pin and V
DD. Connect the switch between the
SHUTDOWN pin and ground. Select normal amplifier opera-
tion by closing the switch. Opening the switch connects the
SHUTDOWN pin to V
DD through the pull-up resistor, activat-
ing micro-power shutdown. The switch and resistor guaran-
tee that the SHUTDOWN pin will not float. This prevents
unwanted state changes. In a system with a microprocessor
or a microcontroller, use a digital output to apply the control
voltage to the SHUTDOWN pin. Driving the SHUTDOWN pin
with active circuitry eliminates the pull up resistor.
TABLE 1. LOGIC LEVEL TRUTH TABLE FOR SHUT-
DOWN OPERATION
SHUTDOWN
OPERATIONAL MODE
Low
Full power, stereo BTL
amplifiers
High
Micro-power Shutdown
SELECTING PROPER EXTERNAL COMPONENTS
Optimizing the LM4816’s performance requires properly se-
lecting external components. Though the LM4816 operates
well when using external components with wide tolerances,
best performance is achieved by optimizing component val-
ues.
The LM4816 is unity-gain stable, giving a designer maximum
design flexibility. The gain should be set to no more than a
given application requires. This allows the amplifier to
achieve minimum THD+N and maximum signal-to-noise ra-
tio. These parameters are compromised as the closed-loop
gain increases. However, low gain demands input signals
with greater voltage swings to achieve maximum output
power. Fortunately, many signal sources such as audio CO-
DECs have outputs of 1V
RMS (2.83VP-P). Please refer to the
Audio Power Amplifier Design section for more informa-
tion on selecting the proper gain.
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value
input coupling capacitor (C
i in Figure 1). A high value capaci-
tor can be expensive and may compromise space efficiency
in portable designs. In many cases, however, the speakers
used in portable systems, whether internal or external, have
little ability to reproduce signals below 150Hz. Applications
using speakers with this limited frequency response reap
little improvement by using large input capacitor.
Besides effecting system cost and size, C
i has an affect on
the LM4816’s click and pop performance. When the supply
voltage is first applied, a transient (pop) is created as the
charge on the input capacitor changes from zero to a quies-
cent state. The magnitude of the pop is directly proportional
to the input capacitor’s size. Higher value capacitors need
more time to reach a quiescent DC voltage (usually V
DD/2)
when charged with a fixed current. The amplifier’s output
charges the input capacitor through the feedback resistor,
R
f. Thus, pops can be minimized by selecting an input
capacitor value that is no higher than necessary to meet the
desired -3dB frequency.
A shown in Figure 1, the input resistor (R
I) and the input
capacitor, C
I produce a 3dB high pass filter cutoff frequency
that is found using Equation (7).
(7)
As an example when using a speaker with a low frequency
limit of 150Hz, C
I, using Equation (4), is 0.063F. The 1.0F
C
I shown in Figure 1 allows the LM4816 to drive high effi-
ciency, full range speaker whose response extends below
30Hz.
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consid-
eration should be paid to value of C
B, the capacitor con-
nected to the BYPASS pin. Since C
B determines how fast
the LM4816 settles to quiescent operation, its value is critical
when minimizing turnon pops. The slower the LM4816’s
outputs ramp to their quiescent DC voltage (nominally 1/2
V
DD), the smaller the turnon pop. Choosing CB equal to
1.0F along with a small value of C
i (in the range of 0.1F to
0.39F), produces a click-less and pop-less shutdown func-
tion. As discussed above, choosing C
i no larger than neces-
sary for the desired bandwidth helps minimize clicks and
pops.
OPTIMIZING CLICK AND POP REDUCTION
PERFORMANCE
The LM4816 contains circuitry to minimize turn-on and shut-
down transients or "clicks and pop". For this discussion,
turn-on refers to either applying the power supply voltage or
when the shutdown mode is deactivated. While the power
supply is ramping to its final value, the LM4816’s internal
amplifiers are configured as unity gain buffers. An internal
current source changes the voltage of the BYPASS pin in a
controlled, linear manner. Ideally, the input and outputs track
LM4816
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4817MH/NOPB | 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO28 |
| LM4818M/NOPB | 0.35 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| LM4820MMX-6 | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| LM4820MMX-6/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| LM4820MX-6/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4816MTX | 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 |
| LM4816MTX/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 |
| LM4817 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1W Stereo Audio Amplifier Plus Adjustable Output Limiter Plus Adjustable LDO |
| LM4817MHX/NOPB | 功能描述:IC AMP AUDIO PWR 1.5W AB 28TSSOP 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:D 類 輸出類型:1-通道（單聲道），帶立體聲耳機(jī) 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:930mW x 1 @ 8 歐姆; 40mW x 2 @ 16 歐姆 電源電壓:2.7 V ~ 5.5 V 特點(diǎn):消除爆音，差分輸入，I²C，靜音，關(guān)閉，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) 其它名稱:MAX97000EWA+T-ND |
| LM4818 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:350mW Audio Power Amplifier with Shutdown Mode |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。