美國(guó)國(guó)家半導(dǎo)體公司（National Semiconductor Corp.）（美國(guó)紐約證券交易所上市代碼：NSM）宣布推出兩款可配置的傳感器模擬前端（AFE）集成電路，兩款產(chǎn)品采用美國(guó)國(guó)家半導(dǎo)體的獨(dú)創(chuàng)技術(shù)，并獲得多款全新設(shè)計(jì)工具的支持，令系統(tǒng)設(shè)計(jì)工程師可以使用各大廠商生產(chǎn)的各類傳感器產(chǎn)品完成信號(hào)路徑設(shè)計(jì)，將產(chǎn)品快速推向市場(chǎng)。

    NS公司的LMP90100是傳感器模擬前端（AFE）系統(tǒng)，是多路低功耗24位的傳感器AFE,具有精密的24位Sigma-Delta ADC和低噪音可編增益放大器（1x - 128x）和全差分高阻抗模擬輸入復(fù)接器。ENOB/NFR高達(dá)21.5/19位，失調(diào)誤差8.4nV,增益誤差7ppm,總噪音小于10 μV-rms,輸出數(shù)據(jù)速率（ODR）為1.6775 SPS - 214.65 SPS,主要用在溫度和壓力發(fā)送器，應(yīng)力儀接口和工業(yè)過(guò)程控制。本文介紹LMP90100主要特性和指標(biāo)， 方框圖，多種典型應(yīng)用和配置電路， LMP90100EB評(píng)估板電路圖和材料清單。

    LMP90100:Sensor AFE System: Multi-Channel, Low Power 24-Bit Sensor AFE with True Continuous Background Calibration

    The LMP90100 is a highly integrated, multi-channel, low power 24-bit Sensor AFE. The device features a precision, 24-bit Sigma Delta Analog-to-Digital Converter （ADC） with a low noise programmable gain amplifier and a fully differential high impedance analog input multiplexer. A true continuous background calibration feature allows calibration at all gains and sample rates without interrupting the signal path. The background calibration feature essentially eliminates gain and offset errors across temperature and time, providing measurement accuracy without sacrificing speed and power consumption.

    Another feature of the LMP90100 is continuous background sensor diagnostics, allowing the detection of open and short circuit conditions and out-of-range signals, without requiring user intervention, resulting in enhanced system reliability.

    Two sets of independent external reference voltage pins allow multiple ratiometric measurements. In addition, two matched programmable current sources are available to excite external sensors such as resistive temperature detectors and bridge sensors. Furthermore, seven GPIO pins are provided for interfacing to external LEDs and switches to simplify control across an isolation barrier.

    Collectively, these features make the LMP90100 a complete analog front-end for low power, precision sensor applications such as temperature, pressure, strain gauge, and industrial process control. The LMP90100 is guaranteed over the extended temperature range of -40℃ to +105℃ and is available in a 28-pin TSSOP package.

    LMP90100主要特性:
    ■ 24-Bit Low Power Sigma Delta ADC
    ■ True Continuous Background Calibration at all gains
    ■ Low-Noise programmable gain (1x - 128x)
    ■ Continuous background open/short and out of range sensor diagnostics
    ■ 8 selectable output data rates (ODR) with single-cycle settling
    ■ 2 matched excitation current sources from 100 μA to 1000 μA
    ■ 4-DIFF / 7-SE flexible and programmable MUX channels
    ■ 7 General Purpose Input/Output pins
    ■ Chopper-stabilized buffer for low offset
    ■ SPI 4 wire serial interface with CRC data link error correction
    ■ Simultaneous 50 Hz & 60 Hz line rejection at ODR ≤13.42 SPS
    ■ Independent gain and ODR selection per channel
    ■ Supported by Webench Sensor AFE Designer
    ■ Automatic Channel Sequencer
    LMP90100主要指標(biāo):
    ■ ENOB/NFR Up to 21.5/19 bits
    ■ Offset Error (typ) 8.4 nV
    ■ Gain Error (typ) 7 ppm
    ■ Total Noise < 10 μV-rms
    ■ Integral Non-Linearity (INL max) ±15 ppm of FSR
    ■ Output Data Rates (ODR) 1.6775 SPS - 214.65 SPS
    ■ Analog Voltage, VA +2.85V to +5.5V
    ■ Digital Input/Output Voltage, VIO +2.7V to +5.5V
    ■ Operating Temp Range -40℃to 105℃
    ■ Package 28-Pin TSSOP
    LMP90100應(yīng)用:
    ■ Temperature and Pressure Transmitters
    ■ Strain Gauge Interface
    ■ Industrial Process Control

圖1.LMP90100方框圖

圖2.LMP90100典型應(yīng)用框圖

圖3.LMP90100應(yīng)用(1):采用雙電流源的3線RTD

圖4.LMP90100應(yīng)用(2):采用單電流源的3線RTD

   圖5.LMP90100應(yīng)用(3):采用CJC熱電偶

    LMP90100評(píng)估板
     The LMP90100 Evaluation Board Design Kit (consisting of the LMP90100 Evaluation Board, the SPIO-4 Digital Controller Board, the Sensor AFE software, and this user’s guide) is designed to ease evaluation and design-in of National Semiconductor’s LMP90100 24-bit Fully Programmable Low Power ADC with True Continuous Background Calibration.
    Data capturing and static evaluations are simplified by connecting the SPIO-4 Digital Controller Board to a PC via USB and running the Sensor AFE software. The data capture board will generate the SPI signals to communicate to and capture data from the LMP90100. The user will also have the option to evaluate the LMP90100 without using the SPIO-4 board or the Sensor AFE software.
    The LMP90100 will digitize the analog input, and the software will display these results in time domain and histogram.
    The software also allows customers to write to and read from registers, to calibrate the device or the system’s gain, offset, and scale settings, and most importantly, to configure and learn about the LMP90100.
    This document describes the connection between the boards and PC, provide a quick start for a normal DC, 3-wire RTD, and thermocouple/temperature sensor applications, describe how to evaluate the board with and without the SPIO-4 board, and provides the schematic and BOM.
    LMP90100評(píng)估板包括:
    1. LMP90100 evaluation board
    2. SPIO-4 digital controller board
    3. Power supplies (optional) to source VA, or VIO, or VREFP.
    4. Multimeter
    5. PC with Sensor AFE software

圖6.LMP90100評(píng)估板外形圖

    圖7.LMP90100 DC讀數(shù)推薦配置圖

    圖8.LMP90100短路輸入和校準(zhǔn)測(cè)試推薦配置圖

圖9.LMP90100 PT-100 RTD讀數(shù)推薦配置圖

圖10.LMP90100 熱電偶和溫度傳感器電路圖

圖11.LMP90100熱電偶推薦配置圖

圖12.LMP90100和LM94022推薦配置圖

    圖13.LMP90100EB評(píng)估板電路圖

圖14.LMP90100EB評(píng)估板材料清單（BOM）

    圖15.LMP90100EB評(píng)估板PCB布局圖：頂層

    價(jià)格及供貨情況

    美國(guó)國(guó)家半導(dǎo)體LMP90100芯片采用28引腳TSSOP封裝，采購(gòu)以1,000顆為單位，單顆售價(jià)為4.95美元，現(xiàn)已批量供貨。LMP91000芯片采用14引腳LLP封裝，采購(gòu)以1,000顆為單位，單顆售價(jià)為3.95美元，同樣已經(jīng)批量供貨。目前美國(guó)國(guó)家半導(dǎo)體正面向更高速率、更高性能的傳感器系統(tǒng)開發(fā)多款傳感器模擬前端電路，該公司也計(jì)劃進(jìn)軍醫(yī)療設(shè)備等產(chǎn)品市場(chǎng)，預(yù)計(jì)這些新產(chǎn)品將于明年推出。

    美國(guó)國(guó)家半導(dǎo)體公司簡(jiǎn)介美國(guó)國(guó)家半導(dǎo)體是一家位居領(lǐng)導(dǎo)地位的電源管理技術(shù)開發(fā)商，一直致力為市場(chǎng)提供各種易于使用的模擬集成電路，而且擁有的供應(yīng)鏈管理技術(shù)及經(jīng)驗(yàn)，備受業(yè)界推崇。該公司的高性能模擬產(chǎn)品可以提高系統(tǒng)的能源效率，因此極受客戶歡迎。美國(guó)國(guó)家半導(dǎo)體的公司總部位于美國(guó)加州圣塔克拉拉（Santa Clara），2010 年財(cái)年的營(yíng)業(yè)額達(dá) 14.2 億美元。