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| 型号： | LM4855IBL/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 11/27页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO PWR 1.5W AB 18USMD |
| 标准包装： | 1 |
| 系列： | Boomer® |
| 类型： | AB 类 |
| 输出类型： | 1-通道（单声道），带立体声耳机 |
| 在某负载时最大输出功率 x 通道数量： | 1.5W x 1 @ 4 欧姆; 115mW x 2 @ 32 欧姆 |
| 电源电压： | 2.6 V ~ 5 V |
| 特点： | 消除爆音，静音，关机，SPI，热保护，音量控制 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 18-uSMD |
| 封装/外壳： | 18-VFBGA |
| 包装： | 标准包装 |
| 其它名称： | LM4855IBLDKR |
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SNAS164C – JUNE 2002 – REVISED MAY 2013
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
θJA is the sum of θJC, θCS, and θSA. (θJC is the junction-to-case thermal impedance,
θCS is the case-to-sink thermal impedance, and θSA is the sink-to-ambient thermal impedance.) Refer to the
Typical Performance Characteristics 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
stabilize 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 LM4855's supply pins and ground. Keep the length of leads and traces that connect capacitors
between the LM4855's power supply pin and ground as short as possible. Connecting a 1F capacitor, CB,
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 turn-on time and can compromise the amplifier's click and pop performance. The selection of bypass
capacitor values, especially CB, depends on desired PSRR requirements, click and pop performance (as
explained in the section Selecting External Components) system cost, and size constraints.
SELECTING EXTERNAL COMPONENTS
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value input coupling capacitor (Ci in Figure 1). A high value
capacitor 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.
The internal input resistor (Ri) and the input capacitor (Ci) produce a high pass filter cutoff frequency that is found
using Equation (9).
fc = 1 / (2πRiCi)
(9)
As an example when using a speaker with a low frequency limit of 150Hz, Ci, using Equation (9) is 0.063F. The
0.22F Ci shown in Figure 1 allows the LM4855 to drive high efficiency, full range speaker whose response
extends below 40Hz.
Copyright 2002–2013, Texas Instruments Incorporated
19
Product Folder Links: LM4855
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4855ITL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述:IC AMP AUDIO 1W MONO SMD 4855 |
| LM4855ITL/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 |
| LM4855ITLX | 制造商:Texas Instruments 功能描述:Audio Amp Headphone/Speaker 1-CH Mono/2-CH Stereo 1.1W Class-AB 18-Pin uSMD T/R |
| LM4855ITLX/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 |
| LM4855LQ | 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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