- 您现在的位置：买卖IC网 > PDF目录30755 > LM4884MH/NOPB (NATIONAL SEMICONDUCTOR CORP) 2.6 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 PDF资料下载
参数资料
| 型号： | LM4884MH/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 2.6 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
| 封装： | TSSOP-20 |
| 文件页数： | 8/22页 |
| 文件大小： | 1189K |
| 代理商： | LM4884MH/NOPB |
Application Information (Continued)
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful bridged or single-ended amplifier. Equation (2)
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)
Single-Ended
(2)
However, a direct consequence of the increased power de-
livered to the load by a bridge amplifier is an increase in the
internal power dissipation point for a bridge amplifier oper-
ating at the same given conditions.
P
DMAX =4*(VDD)
2/(2
π2R
L)
Bridge Mode
(3)
The LM4884 has four operational amplifiers in one package
and the maximum internal power dissipation is four times
that of a single-ended amplifier. From Equation (3), assum-
ing a 5V power supply and an 8
load, the maximum power
dissipation point is 2W. The maximum power dissipation
point obtained from Equation (3) must not exceed the power
dissipation predicted by Equation (4):
P
DMAX =(TJMAX TA)/
θ
JA
(4)
For the exposed DAP TSSOP package,
θ
JA=
41C/W.
T
JAMAX = 150C for the LM4884. For a given ambient tem-
perature T
A, Equation (4) can be used to find the maximum
internal power dissipation supported by the IC packaging. If
the result of Equation (3) is greater than that of Equation (4),
decrease the supply voltage, increase the load impedance,
or reduce the ambient temperature. For a typical application
with a 5V power supply and an 8
load, the maximum
ambient temperature that does not violate the maximum
junction temperature is approximately 68C. This further as-
sumes 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 am-
bient temperatures are allowed as output power decreases.
Refer to the Typical Performance Characteristics curves for
power dissipation information at lower output power levels.
BTL GAIN SELECTION
The LM4884 features four fixed, internally set, BTL voltage
gains: 6dB, 10dB, 15.6dB, and 21.6dB. Select one of the
four gains by applying a logic level signal to the GAIN0
(MSB) and GAIN1 (LSB) digital inputs.
The closed-loop gain of the first amplifier is adjustable, hav-
ing four different gains, whereas two internal 20k
resistors
set the second amplifier’s gain at -1. Table 1 below, shows
the state of the two logic inputs required to select one of the
four gain values.
Table 1. Gain Settings and Input Resistance
GAIN 0 GAIN 1
Selected Gain
(dB)
Input Resistance
(R
i)
0
6
90k
0
1
10
70k
1
0
15.6
45k
1
21.6
25k
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection. The capacitors connected to the bypass and power
supply pins should be placed as close to the LM4884 as
possible. The capacitor connected between the bypass pin
and ground improves the internal bias voltage’s stability,
producing improved PSRR. The improvements to PSRR
increase as the bypass pin capacitor value increases.
Typical applications employ a 5V regulator with 10F and a
0.1F filter capacitors that aid in supply stability. Their pres-
ence, however, does not eliminate the need for bypassing
the LM4884’s supply pins. The selection of bypass capacitor
values, especially C
B, depends on desired PSRR require-
ments, click and pop performance (as explained in theSe-
lecting External Components section), system cost, and
size constraints.
MICRO-POWER SHUTDOWN
The LM4884 features an active-low micro-power shutdown
mode. The voltage applied to the SHUTDOWN pin controls
the LM4884’s shutdown function. Activate micro-power shut-
down by applying 0V to the SHUTDOWN pin. The logic
threshold is typically 0.4V for a logic low and 1.5V for a logic
high. When active, the LM4884’s micro-power shutdown
feature turns off the amplifier’s bias circuitry, disables the
internal V
DD/2 generator, and forces the amplifier outputs
into a high impedance state. The result is greatly reduced
power supply current. The low 0.1A typical shutdown cur-
rent is achieved by applying a voltage to the SHUTDOWN
pin that is as near to GND as possible. A voltage that is
greater than GND may increase the shutdown current.
There are a few methods to control the micro-power shut-
down. These include using a single-pole, single-throw switch
(SPST), a microprocessor, or a microcontroller. When using
a switch, connect a 100k
pull-down resistor between the
SHUTDOWN pin and GND and the SPST switch between
the SHUTDOWN pin and V
DD. Select normal amplifier op-
eration by closing the switch. Opening the switch applies
GND to the SHUTDOWN pin, activating micro-power shut-
down. The switch and resistor guarantee that the SHUT-
DOWN pin will not float. This prevents unwanted state
changes. In a system with a microprocessor or a microcon-
troller, use a digital output to apply the active-state voltage to
the SHUTDOWN pin. Driving the SHUTDOWN pin with ac-
tive circuitry eliminates the pull-down resistor.
LM4884
www.national.com
16
相关PDF资料 |
PDF描述 |
|---|---|
| LM4888SQ/NOPB | 3 W, 2 CHANNEL, AUDIO AMPLIFIER, QCC24 |
| LM4889ITL/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA8 |
| LM4889ITLX/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA8 |
| LM4889LD/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO10 |
| LM4890LD/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, DSO10 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4884MHX/NOPB | 功能描述:IC AMP AUDIO 2.6W STER 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) |
| LM48860 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Ground-Referenced, Ultra Low Noise, Fixed Gain Stereo Headphone Amplifier |
| LM48860TL | 制造商:Texas Instruments 功能描述:Audio Amp Headphone 2-CH Stereo 0.05W Class-AB 12-Pin Micro SMD T/R 制造商:Texas Instruments 功能描述:CLASS D AMP, STERO, 0.04W, 12MICRO |
| LM48860TL/NOPB | 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 |
| LM48860TLBD | 功能描述:音频 IC 开发工具 LM48860TL EVAL BOARD RoHS:否 制造商:Texas Instruments 产品:Evaluation Kits 类型:Audio Amplifiers 工具用于评估:TAS5614L 工作电源电压:12 V to 38 V |
发布紧急采购，3分钟左右您将得到回复。