基于LMP8358的高精度可编增益仪表放大器设计方案
NS公司的LMP8358是高精度可编增益仪表放大器,通过SPI兼容的串口或并口可把增益编程为0,20,50,100,200,500,或1000,也可用两个外设电阻设定为任意值.单电源2.7V到5.5V工作,电流为1.8mA,增益zui大误差为0.15%,增益漂移为16ppm/℃,CMRR大于110dB,失调电压小于10μV,失调电压漂移小于50nV/℃,增益带宽GBW(增益=10)8MHz,非线性小于100ppm,主要用在桥接传感器放大,热堆放大,手提仪表,医疗设备.本文主要介绍LMP8358主要特性,功能方框图,典型应用方框图,菊花和星形链接配置图以及差分桥接传感器应用电路图.
TheLMP8358isaprecisionprogrammable-gaininstrumentationamplifierinNational’sLMPprecisionamplifierfamily.Itsgaincanbeprogrammedto10,20,50,100,200,500,or1000throughanSPI-compatibleserialinterfaceorthroughaparallelinterface.Alternatively,itsgaincanbesettoanarbitraryvalueusingtwoexternalresistors.TheLMP8358usespatentedtechniquestomeasureandcontinuouslycorrectitsinputoffsetvoltage,eliminatingoffsetdriftovertimeandtemperatureandtheeffectof1/fnoise.Itsground-sensingCMOSinputfeaturesahighCMRRandlowinputbiascurrents.Itiscapableofsensingdifferentialinputvoltagesinacommonmoderangethatextendsfrom100mVbelowthenegativesupplyto1.4Vbelowthepositivesupply,makingitanidealsolutionforinterfacingwithground-referencedsensors,supply-referencedsensorbridges,andanyotherapplicationrequiringprecisionandlong-termstability.Additionally,theLMP8358includesfaultdetectioncircuitrytodetectopenandshortedinputsanddeterioratingconnectionstothesignalsource.OtherfeaturesthatmaketheLMP8358aversatilesolutionformanyapplicationsareitsrail-to-railoutput,lowinputvoltagenoiseandhighgain-bandwidthproduct.
LMP8358主要特性:
TypicalValuesunlessotherwisenoted,TA=25℃
■Supplyvoltage2.7Vto5.5V
■Supplycurrent1.8mA
■Maxgainerror0.15%
■Maxgaindrift16ppm/℃
■MinCMRR110dB
■Maxoffsetvoltage10μV
■Maxoffsetvoltagedrift50nV/℃
■GBW(gain=10)8MHz
■Maxnon-linearity100ppm
■Operatingtemperaturerange−40℃to125℃
■Inputfaultdetection
■SPIorpinconfigurablemodes
■EMIRRat1.8GHz92dB
■14-PinSOICand14-PinTSSOPPackage
LMP8358应用:
■Bridgesensoramplifier
■Thermopileamplifier
■Portableinstrumentation
■Medicalinstrumentation
■Precisionlow-sidecurrentsensing
图1.LMP8358方框图
图2.LMP8358典型应用方框图
图3.LMP8358菊花链接配置图
图4.LMP8358每个寄存器不同写入值的星形链接配置图
图5.LMP8358差分桥接传感器应用电路图
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(本文转自电子工程世界:http://.cn/mndz/2011/0221/article_5044.html)