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3.4OutputOpAmp
EVMOperation
Table3.DACOutputChannelMapping
ReferenceJumperPositionFunction
1-2DACoutputA(V
OUT
A)isroutedtoJ4-2.
JMP11
2-3DACoutputA(V
OUT
A)isroutedtoJ4-10.
1-2DACoutputB(V
OUT
B)isroutedtoJ4-4.
JMP12
2-3DACoutputB(V
OUT
B)isroutedtoJ4-12.
1-2DACoutputC(V
OUT
C)isroutedtoJ4-6.
JMP13
2-3DACoutputC(V
OUT
C)isroutedtoJ4-14.
1-2DACoutputD(V
OUT
D)isroutedtoJ4-8.
JMP14
2-3DACoutputD(V
OUT
D)isroutedtoJ4-16.
InordertoallowexclusivecontrolofeachEVM,differentSYNCsignalsmustbeselectedforeach
DAC8555.Thisdifferenceisnoteasilyaccomplishedasitinvolveshardwarealterations.TheEVMboard
thatsitsonthebottomofthestackcanusetheSYNCsignalcomingfromJ2B-7.ThepinofJ2A-7canbe
cutsothattheSYNCsignalcomingfromthebottomEVMboardinthestackdoesnotpassthrough.The
EVMboardthatsitsontopcanusetheCNTLsignalcomingfromJ2-1.ThesignalofJ2-1mustbe
jumperedacrosstoJ2-7oftheEVMboardthatsitsonthetopofthestack.TheLDAC,SYNCand
ENABLEcontrolsignalsareshared.TheDAC8555onlyrespondswhenthecorrectSYNCsignalis
generated.
TherawoutputsoftheDACcanbeprobedthroughtheevennumberedpinsofJ4,theoutputterminal,
whichalsoprovidesmechanicalstabilitywhenstackingorpluggingintoanyinterfacecard.Inaddition,it
provideseasyaccessformonitoringuptoeightDACchannelswhenstackingtwoEVMstogether.
TheDAC8555EVMincludesanoptionalsignalconditioningcircuitfortheDACoutputthroughanexternal
operationalamplifier,U2.Theoutputopampissettounitygainconfigurationbydefault.OnlyoneDAC
outputchannelcanbemonitoredatanygiventime.JMP15selectswhichpinofJ4istheinput.EitherJ4-1
orJ4-3canbeusedastheopampsignalinput.ThedefaultsettingforJMP15selectsJ4-1.Ashorting
jumpercanbeplacedbetweenoneoftheDACoutputsandtheopampinput.Forexample,ajumper
acrossJ4-1andJ4-2placestheDACAoutputastheinputfortheopampifboardjumpersareinthe
defaultposition.IfJMP15isinthealternateposition,thenashortingblockbetweenJ4-3andJ4-2makes
theDACBoutputtheinputtotheopamp.
TheoutputofU2passesthroughJMP16.Inthedefaultposition,theoutputconnectstoJ4-5.When
JMP16isinthealternateposition,theoutputfromU2connectstoJ4-7.Theoutputcanbemonitored
from,orpassedto,anotherdevicefromtheJ4connector.
ThejumperarrangementofJMP15andJMP16connectingtoJ4allowsU2tobeusedinthestacked
boardarrangementdiscussedaboveinSection3.3.
Thefollowingsubsectionsdescribethedifferentconfigurationsoftheoutputamplifier,U2.
SLAU204–December2006DAC8555EVMUser'sGuide17
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