www.德州仪器.com
V
OUTDIFF
V
OUT1
V
OUT2
(7)
V
OUTDIFF
(
2
代号
4095
)
4096
I
OUTFS
R
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(8)
AnalogOutputs
AVDD
电流 源排列
IOUT1 IOUT2
s(1) s(1)c
R
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R
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s(2) s(2)c s(n) s(n)c
OutputConfigurations
DAC5662
SLAS425–JULY2004
applicationinformation(持续)
thetotaldifferentialoutputvoltageis:
figure20.analogoutputs
thedac5662providestwocomplementarycurrentoutputs,iout1andiout2.thesimplifiedcircuitofthe
analogoutputstagerepresentingthedifferentialtopologyisshowninfigure20.theoutputimpedanceofiout1
andiout2resultsfromtheparallelcombinationofthedifferentialswitches,alongwiththecurrentsourcesand
associatedparasiticcapacitances.
thesignalvoltageswingthatmaydevelopatthetwooutputs,iout1andiout2,islimitedbyanegativeand
positivecompliance.thenegativelimitof–1visgivenbythebreakdownvoltageofthecmosprocessand
exceedingitcompromisesthereliabilityofthedac5662orevencausespermanentdamage.withthefull-规模
outputsetto20ma,thepositivecomplianceequals1.2v.notethatthecompliancerangedecreasestoabout1
vforaselectedoutputcurrentofioutfs=2ma.careshouldbetakenthattheconfigurationofdac5662does
notexceedthecompliancerangetoavoiddegradationofthedistortionperformanceandintegrallinearity.
bestdistortionperformanceistypicallyachievedwiththemaximumfull-scaleoutputsignallimitedto
approximately0.5vpp.thisisthecasefora50-
Ω
doublyterminatedloadanda20-mafull-scaleoutputcurrent.
AvarietyofloadscanbeadaptedtotheoutputoftheDAC5662byselectingasuitabletransformerwhile
maintainingoptimumvoltagelevelsatiout1andiout2.此外,usingthedifferentialoutputconfiguration
incombinationwithatransformerwillbeinstrumentalforachievingexcellentdistortionperformance.
一般-modeerrors,suchaseven-orderharmonicsornoise,canbesubstantiallyreduced.thisisparticularly
thecasewithhighoutputfrequencies.
forthoseapplicationsrequiringtheoptimumdistortionandnoiseperformance,itisrecommendedtoselecta
全部-scaleoutputof20ma.alowerfull-scalerangeof2mamaybeconsideredforapplicationsthatrequirelow
powerconsumption,butcantolerateaslightreductioninperformancelevel.
thecurrentoutputsofthedac5662allowforavarietyofconfigurations.asmentionedpreviously,utilizingthe
转换器’sdifferentialoutputsyieldthebestdynamicperformance.suchadifferentialoutputcircuitmayconsist
ofanrftransformeroradifferentialamplifierconfiguration.thetransformerconfigurationisidealformost
applicationswithaccoupling,whileopampswillbesuitableforadc-coupledconfiguration.
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