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参数资料
| 型号： | LM4866LQ/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 3.2 W, 2 CHANNEL, AUDIO AMPLIFIER, PQCC24 |
| 封装： | LLP-24 |
| 文件页数： | 4/21页 |
| 文件大小： | 1013K |
| 代理商： | LM4866LQ/NOPB |
Application Information (Continued)
fier. From Equation (3), assuming a 5V power supply and an
4
load, the maximum single channel power dissipation is
1.27W or 2.54W for stereo operation.
P
DMAX =4x(VDD)
2 /(2
π2 R
L) Bridge Mode
(3)
The LM4973’s power dissipation is twice that given by Equa-
tion (2) or Equation (3) when operating in the single-ended
mode or bridge mode, respectively. Twice the maximum
power dissipation point given by Equation (3) must not ex-
ceed the power dissipation given by Equation (4):
P
DMAX’= (TJMAX TA)/
θ
JA
(4)
The LM4866’s T
JMAX = 150C. In the LQ (LLP) package
soldered to a DAP pad that expands to a copper area of 5in
2
on a PCB, the LM4866’s
θ
JA is 20C/W. In the MTE package
soldered to a DAP pad that expands to a copper area of 2in
2
on a PCB , the LM4866’s
θ
JA is 41C/W. At any given
ambient temperature T
J\A, use Equation (4) to find the maxi-
mum internal power dissipation supported by the IC packag-
ing. Rearranging Equation (4) and substituting PDMAX for
PDMAX’ results in Equation (5). This equation gives the
maximum ambient temperature that still allows maximum
stereo power dissipation without violating the LM4866’s
maximum junction temperature.
T
A =TJMAX 2xPDMAX
θ
JA
(5)
For a typical application with a 5V power supply and an 4
load, the maximum ambient temperature that allows maxi-
mum stereo power dissipation without exceeding the maxi-
mum junction temperature is approximately 99C for the LLP
package and 45C for the MTE package.
T
JMAX =PDMAX
θ
JA +TA
(6)
Equation (6) gives the maximum junction temperature T
J-
MAX
. If the result violates the LM4866’s 150C, reduce the
maximum junction temperature by reducing the power sup-
ply voltage or increasing the load resistance. Further allow-
ance should be made for increased ambient temperatures.
The above examples assume that a device is a surface
mount part operating around the maximum power dissipation
point. Since internal power dissipation is a function of output
power, higher ambient temperatures are allowed as output
power or duty cycle decreases.
If the result of Equation (2) is greater than that of Equation
(3), then decrease the supply voltage, increase the load
impedance, or reduce the ambient temperature. If these
measures are insufficient, a heat sink can be added to
reduce
θ
JA. The heat sink can be created using additional
copper area around the package, with connections to the
ground pin(s), supply pin and amplifier output pins. External,
solder attached SMT heatsinks such as the Thermalloy
7106D can also improve power dissipation. When adding a
heat sink, the
θ
JA is the sum of
θ
JC,
θ
CS, and
θ
SA.(
θ
JC is the
junctiontocase thermal impedance,
CS is the casetosink
thermal impedance, and
θ
SAis the sinktoambient thermal
impedance.) Refer to the Typical Performance Characteris-
tics curves for power dissipation information at lower output
power levels.
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
LM4866’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 LM4866’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
LM4866’s shutdown function. Activate micro-power shut-
down by applying V
DD to the SHUTDOWN pin. When active,
the LM4866’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 0.7A 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
LM4866
www.national.com
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相关PDF资料 |
PDF描述 |
|---|---|
| LM4866LQX/NOPB | 3.2 W, 2 CHANNEL, AUDIO AMPLIFIER, PQCC24 |
| LM4866MTX/NOPB | 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| LM4868MTE/NOPB | 3 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| LM4868MTEX/NOPB | 3 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| LM4868MT/NOPB | 1.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4866MT | 制造商:Texas Instruments 功能描述:AMP AUDIO STEREO 2W SMD SSOP20 |
| LM4866MT/NOPB | 功能描述:IC AMP AUDIO PWR 3.2W AB 20TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4866MTE | 制造商:Texas Instruments 功能描述:AMP AUDIO STEREO 2W SMD TSSOP20 |
| LM4866MTE/NOPB | 功能描述:音频放大器 2.2W Stereo Audio Amp RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| LM4866MTEX | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
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