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參數(shù)資料
| 型號： | LM4809M |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 0.105 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| 封裝： | M08A |
| 文件頁數(shù)： | 13/14頁 |
| 文件大小： | 694K |
| 代理商： | LM4809M |
Typical Performance Characteristics (Continued)
Application Information
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the
LM4809’s shutdown function. Activate micro-power shut-
down by applying a logic low voltage to the SHUTDOWN pin.
The logic threshold is typically V
DD/2. When active, the
LM4809’s micro-power shutdown feature turns off the ampli-
fier’s bias circuitry, reducing the supply current. The low
0.4A typical shutdown current is achieved by applying a
voltage that is as near as GND as possible to the SHUT-
DOWN pin. A voltage that is above GND 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 100k
pull-down resistor between the
SHUTDOWN pin and GND. Connect the switch between the
SHUTDOWN pin and V
DD. Select normal amplifier operation
by closing the switch. Opening the switch connects the
SHUTDOWN pin to GND through the pull-down resistor,
activating micro-power shutdown. The switch and resistor
guarantee that the SHUTDOWN pin will not float. This pre-
vents unwanted state changes. In a system with a micropro-
cessor or a microcontroller, use a digital output to apply the
control voltage to the SHUTDOWN pin. Driving the SHUT-
DOWN pin with active circuitry eliminates the pull-down re-
sistor.
POWER DISSIPATION
Power dissipation is a major concern when using any power
amplifier and must be thoroughly understood to ensure a
successful design. Equation 1 states the maximum power
dissipation point for a single-ended amplifier operating at a
given supply voltage and driving a specified output load.
P
DMAX =(VDD)
2 /(2
π2R
L)
(1)
Since the LM4809 has two operational amplifiers in one
package, the maximum internal power dissipation point is
twice that of the number which results from Equation 1. Even
with the large internal power dissipation, the LM4809 does
not require heat sinking over a large range of ambient tem-
perature. From Equation 1, assuming a 5V power supply and
a32
load, the maximum power dissipation point is 40mW
per amplifier. Thus the maximum package dissipation point
is 80mW. The maximum power dissipation point obtained
must not be greater than the power dissipation that results
from Equation 2:
P
DMAX =(TJMAX TA)/ θJA
(2)
For package MUA08A,
θ
JA = 210C/W. TJMAX = 150C for
the LM4809. Depending on the ambient temperature, T
A,of
the system surroundings, Equation 2 can be used to find the
maximum internal power dissipation supported by the IC
packaging. If the result of Equation 1 is greater than that of
Equation 2, then either the supply voltage must be de-
creased, the load impedance increased or T
A reduced. For
the typical application of a 5V power supply, with a 32
load,
the maximum ambient temperature possible without violating
the maximum junction temperature is approximately 133.2C
provided that device operation is around the maximum
power dissipation point. Power dissipation is a function of
output power and thus, if typical operation is not around the
maximum power dissipation point, the ambient temperature
may be increased accordingly. Refer to the Typical Perfor-
mance Characteristics curves for power dissipation infor-
mation for lower output powers.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection. Applications that employ a 5V regulator typically
use a 10F in parallel with a 0.1F filter capacitors to stabi-
lize the regulator’s output, reduce noise on the supply line,
and improve the supply’s transient response. However, their
presence does not eliminate the need for a local 1.0F
tantalum bypass capacitance connected between the
LM4809’s supply pins and ground. Keep the length of leads
and traces that connect capacitors between the LM4809’s
power supply pin and ground as short as possible. Connect-
ing a 4.7F 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, however, increases the amplifier’s turn-on time. The
selection of bypass capacitor values, especially C
B, depends
on desired PSRR requirements, click and pop performance
(as explained in the section, Selecting Proper External
Components), system cost, and size constraints.
Open Loop
Frequency Response
DS200090-51
Open Loop
Frequency Response
DS200090-38
Supply Current vs
Supply Voltage
DS200090-44
LM4809
www.national.com
8
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4809MA | 制造商:OC White Company 功能描述:Audio Amp Headphone 2-CH Stereo 0.105W Class-AB 8-Pin SOIC N Rail |
| LM4809MA/NOPB | 功能描述:IC AMP AUDIO PWR .105W AB 8SOIC 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) |
| LM4809MBD | 功能描述:BOARD EVALUATION LM4809M RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 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:1 系列:- |
| LM4809MM | 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 |
| LM4809MM/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 |
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