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应用笔记

了解MEMS麦克风有助于提高系统设计效率

AN-1112:麦克风技术规格解析

与ADI公司的其它产品相比,MEMS麦克风的输入为声压波。因此,MEMS麦克风数据手册的某些技术规格可能不为大家所熟悉,或者虽然熟悉,但其应用方式却比较陌生。这篇4页的应用笔记解释了MEMS麦克风数据手册中出现的技术规格和术语,有助于设计人员提高麦克风的系统设计效率。

合适的贴装技术有助MEMS麦克风提供最佳性能

AN-1003:ADMP421底部端口数字MEMS麦克风贴装和连接建议

ADMP421高性能、底部端口、数字MEMS麦克风具有最高15 kHz的平坦宽带频率响应。虽然麦克风自身响应在工作范围内极少变化,但将麦克风放入器件外壳时,自身响应可能会发生改变。这篇8页的应用笔记提供一些贴装建议,以便最大程度地减小封装对最终产品内麦克风性能的影响。另外还探讨了电气连接、编解码器接口和性能等。

使用交流耦合耳机时,保护编解码器免受短路影响

AN-1056:低功耗编解码器ADAU1361和ADAU1761的无电容耳机虚地短路保护

低功耗音频编解码器ADAU1361和ADAU1761内置一个可在无电容耳机模式下工作的立体声耳机放大器。这意味着无需串联交流耦合电容便可获得立体声耳机输出。在无电容耳机输出模式下,编解码器产生虚地基准电压,而不是实地中心电压。虽然这种配置对大多数应用都有效,但如果耳机插孔也用于线路输出,并且连接一个负载,使虚地对实地短路,那么就会引起一些问题。此时,高电流可能会损坏编解码器。这篇2页的应用笔记说明在无电容耳机模式下使用编解码器时,如何实现一个接地检测电路。

使用多格式视频解码器时,可利用一个简单程序压缩脚本,节省存储器空间

AN-1050:ADV74xx/ADV75xx/ADV76xx/ADV78xx压缩I2C脚本的方法

这篇20页的应用笔记介绍一种针对微控制器平台压缩大批I2C脚本的方法,适合需要将50个以上脚本放入单个微控制器存储器中的应用。它包括一个免费(GNU/GPL许可证)倍频程程序的脚本,可用来压缩脚本,并通过解压缩程序将结果导出为C语言代码。

实验室电路

新产品简介

June 2011

High-efficiency filterless 2.5-W monophonic Class-D Audio Amplifier

ssm2377The SSM2377 monophonic class-D audio amplifier can deliver 2.5 W of continuous output power into a 4-Ω load—or 1.4 W into an 8-Ω load—with 92% efficiency, 100‑dB signal-to-noise ratio (SNR), and less than 1% distortion—allowing it to drive speakers directly in mobile phones, MP3 players, and other battery-powered devices. Its design minimizes clicks and pops, turn-on glitches, and EMI emissions—and provides thermal shutdown and short-circuit protection. Pin programming sets the gain of the fully differential input signal path to 6 dB or 12 dB. Radiated EMI emissions are ultralow, allowing the device, with 50-cm unshielded speaker cable, to pass FCC Class  B testing without requiring any external filtering. Operating on a single 2.5-V to 5.5-V supply, the SSM2377 draws 2.5 mA in normal mode and 100 nA in shutdown mode. Available in a 9-ball WLCSP package, it is specified from –40°C to +85°C and priced at $0.59 in 1000s.

SHARC Processors

adsp-21478/79The ADSP-21478 and ADSP-21479 fourth-generation low-power SHARC® processors offer increased performance, hardware-based filter accelerators, audio- and application-focused peripherals, and up to 5 Mbits of SRAM, making them ideal for professional and automotive audio applications. Their single-instruction, multiple-data (SIMD) core supports 32-bit fixed-point and 32-/40-bit floating-point arithmetic formats—performing up to 1800 MFLOPS with a 300-MHz clock. The variable instruction-set architecture (VISA) allows code to be decreased by 20% to 30%, increasing the available memory. Application-specific peripherals simplify hardware design, minimize design risks, and reduce time to market. The software-programmable signal routing unit (SRU) enables flexible routing of digital applications interface (DAI) blocks. Peripherals connected through the SRU include serial ports, SPI ports, S/PDIF transceiver, and an 8-channel asynchronous sample-rate-converter block. The digital peripheral interface (DPI) includes a UART and a two-wire interface. FIR, IIR, and FFT accelerators increase the total system performance. The DMA controller can transfer data from the serial ports to external 16-bit SDR SDRAMs through a glueless interface. All SHARC processors are pin- and code compatible. Specified from 0°C to +70°C (K-grade) or –40°C to +85°C (B-grade), the ADSP-21478/79 are available in 100-lead LQFP and 196-ball CSP-BGA packages and priced from $7.99 in 1000s.

Blackfin Embedded Processor

adsp-bf592The ADSP-BF592 Blackfin processors—optimized for cost-sensitive industrial, automotive, and medical applications—combine the multimedia signal-processing power of a single-instruction, multiple-data (SIMD) DSP with the control capabilities of a RISC microcontroller. With two 16-bit MACs, two 40-bit ALUs, four 8-bit video ALUs, and 132K bytes of core-addressable memory, they operate at up to 400 MHz. 64K bytes of factory-programmed instruction ROM contains VDK RTOS and C-runtime libraries. Peripherals include four timer/counters (three with PWM); two full-duplex synchronous serial ports (SPORTs) that support eight channels of I2S stereo audio; two SPI ports; one UART with IrDA support; a parallel peripheral interface (PPI) that supports ITU-R 656 video formats; a two-wire interface (TWI) controller; nine peripheral DMAs; two memory-to-memory DMA channels, an event handler, 32 GPIOs, a JTAG debugging interface, and a PLL. Specified from 0°C to +70°C (K-grade) or –40°C to +85°C (B-grade), the ADSP-BF592 is available in a 64-lead LFCSP package and priced from $3.56 in 1000s.

9-channel LED Driver includes charge pump, automated lighting effects

adp8866The ADP8866 LED driver combines programmable backlight LED driving with automatic blinking functions. Nine LED drivers are independently programmable at currents up to 25 mA. Once programmed, the current level, fade time, and blinking rate are executed autonomously on a loop. Separate fade-in and fade-out times can be set for the backlight LEDs. A two-capacitor charge pump, which can provide up to 240 mA, powers the drivers. The robust design includes soft start and protection against short circuits, overvoltage, and over-temperature. Operating with a single 2.5-V to 5.5-V supply, the ADP8866 draws 1.2 mA in switching mode and 0.25 μA in standby mode. Available in a 20-lead LFCSP package, it is specified from –40°C to +105°C and priced at $1.48 in 1000s.

2011年5月

采用逻辑电平控制的高端电源开关

adp197 ADP197是一款高端电源开关,可将闲置负载的电源断开,以延长移动电话、数码相机和音频器件的电池使用时间。通过12 mΩ导通电阻,N沟道MOSFET开关元件可最大程度地减少功率损耗,同时可处理高达3 A的连续电流。片内电平转换器确保与现代处理器和控制器逻辑兼容。ADP197采用1.8 V至5.5 V单电源供电,使能时耗用的地电流为18 μA,关断时为100 nA。它采用紧凑的6引脚1 mm x 1.5 mm WLCSP封装,额定温度范围为–40°C至+85°C,千片订量报价为0.46美元/片。

2011年4月

I/O扩展器和键盘控制器

adp5589 ADP5589I/O端口扩展器和键盘矩阵控制器针对需要大键盘矩阵和/或扩展I/O线的便携式和非便携式设备而设计。它能处理所有按键扫描和解码,使主处理器不必监控键盘,从而降低功耗并提高其它功能的可用带宽。当有新的按键事件发生或者通用输入发生变化时,它通过一条中断线通知主处理器。片内FIFO最多可以存储16个事件,通过I2C兼容型接口可以读取这些事件。它还具有可编程逻辑功能和可编程PWM发生器,支持将其它常见功能集成到电路板设计。ADP5589采用24引脚LFCSP封装,千片订量报价为1.20美元/片。

技术文章

Ian Beavers, Joe Triggs, and Lie Dou, 在家庭影院系统设计中使用HDMI收发器, Analog Dialogue, 2/1/2011

Ian Beavers, Joe Triggs, and Lie Dou, 在家庭影院系统设计中使用HDMI收发器,, EE Times, 1/20/2011

Miguel Chavez, 扬声器系统的自动均衡、分频和对齐, ALMA International, 1/5/2011

网络研讨会和教程

运算放大器简介 -- 本研讨会旨在向模拟设计新手或不熟悉模拟设计或概念者介绍运算放大器的基本知识。

实用放大器噪声原理 -- 本研讨会重点向电路板设计人员介绍一些实用的噪声处理技巧,而不是教科书中常见的理论知识。

现场可编程门阵列(FPGA)的供电 -- 现场可编程门阵列(FPGA)的供电——了解基础知识——本研讨会讨论现场可编程门阵列(FPGA)的特殊电源要求,以及用来确保无故障工作的合适电源产品。其中特别介绍一种针对高性能FPGA的供电要求而优化的多功能DC-DC调节器。

 

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