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| 型号： | LM4674SQX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 5/27页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO PWR 2.5W STER 16LLP |
| 产品培训模块： | PowerWise® Products and Technology |
| 标准包装： | 4,500 |
| 系列： | Boomer® |
| 类型： | D 类 |
| 输出类型： | 2 通道（立体声） |
| 在某负载时最大输出功率 x 通道数量： | 2.5W x 2 @ 4 欧姆 |
| 电源电压： | 2.4 V ~ 5.5 V |
| 特点： | 消除爆音，差分输入，PWM，短路保护，关机 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 16-LLP-EP（4x4） |
| 封装/外壳： | 16-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 配用： | LM4674SQBD-ND - BOARD EVALUATION LM4674SQ |
| 其它名称： | LM4674SQX |
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SNAS344E – DECEMBER 2005 – REVISED APRIL 2013
AUDIO AMPLIFIER INPUT CAPACITOR SELECTION
Input capacitors may be required for some applications, or when the audio source is single-ended. Input
capacitors block the DC component of the audio signal, eliminating any conflict between the DC component of
the audio source and the bias voltage of the LM4674. The input capacitors create a high-pass filter with the input
resistance Ri. The -3dB point of the high pass filter is found using Equation (1) below.
f = 1 / 2
πRiCi
(1)
The values for Ri can be found in the EC table for each gain setting.
The input capacitors can also be used to remove low frequency content from the audio signal. Small speakers
cannot reproduce, and may even be damaged by low frequencies. High pass filtering the audio signal helps
protect the speakers. When the LM4674 is using a single-ended source, power supply noise on the ground is
seen as an input signal. Setting the high-pass filter point above the power supply noise frequencies, 217 Hz in a
GSM phone, for example, filters out the noise such that it is not amplified and heard on the output. Capacitors
with a tolerance of 10% or better are recommended for impedance matching and improved CMRR and PSRR.
AUDIO AMPLIFIER GAIN SETTING
The LM4674 features four internally configured gain settings. The device gain is selected through the two logic
inputs, G0 and G1. The gain settings are as shown in the following table.
LOGIC INPUT
GAIN
G1
G0
V/V
dB
0
2
6
0
1
4
12
1
0
8
18
1
16
24
PCB LAYOUT GUIDELINES
As output power increases, interconnect resistance (PCB traces and wires) between the amplifier, load and
power supply create a voltage drop. The voltage loss due to the traces between the LM4674 and the load results
in lower output power and decreased efficiency. Higher trace resistance between the supply and the LM4674 has
the same effect as a poorly regulated supply, increasing ripple on the supply line, and reducing peak output
power. The effects of residual trace resistance increases as output current increases due to higher output power,
decreased load impedance or both. To maintain the highest output voltage swing and corresponding peak output
power, the PCB traces that connect the output pins to the load and the supply pins to the power supply should
be as wide as possible to minimize trace resistance.
The use of power and ground planes will give the best THD+N performance. In addition to reducing trace
resistance, the use of power planes creates parasitic capacitors that help to filter the power supply line.
The inductive nature of the transducer load can also result in overshoot on one or both edges, clamped by the
parasitic diodes to GND and VDD in each case. From an EMI standpoint, this is an aggressive waveform that
can radiate or conduct to other components in the system and cause interference. In is essential to keep the
power and output traces short and well shielded if possible. Use of ground planes beads and micros-strip layout
techniques are all useful in preventing unwanted interference.
As the distance from the LM4674 and the speaker increases, the amount of EMI radiation increases due to the
output wires or traces acting as antennas become more efficient with length. Ferrite chip inductors places close
to the LM4674 outputs may be needed to reduce EMI radiation.
Copyright 2005–2013, Texas Instruments Incorporated
13
Product Folder Links: LM4674
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4674TL | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Filterless 2.5W Stereo Class D Audio Power Amplifier |
| LM4674TL/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 |
| LM4674TLBD | 功能描述:音频 IC 开发工具 LM4674 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 |
| LM4674TLX | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM4674TLX/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 |
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