
SEC ASIC
DAC1350X
10BIT75MSPSQuadDAC
ANALOG
FUNCTION DESCRIPTION
Thisisquad 10bit 75MSPS digital toanalog
data converterand usescurrent-segment
architecturefor4-bitsinMSBsidesand
binary-weightedarchitecturefor6-bitsinLSB
sides.Itcontainsof1'st latch block,decoder
block,2'nd latch block,OPAblock,CM
(currentmirror) block,BGR(Band Gap
Reference)block,Auto-load detectblockand
analog switch block,etc.Thiscoreusesreference
currentwhich decidethe1LSBcurrentby
dividing thereference currentby 32times.Sothe
reference currentmustbe constantand it can be
constantby using OPAblockwith high DCgain.
Themostsignificantblock ofthiscoreisanalog
switch blockand it mustmaintaintheuniformity
ateachswitch,solayoutdesignermustcareof
it.And morethan 90%ofsupplycurrent is
dissipatedatanalog outputside.And it uses
samsung standardcell asall digitalcell oflatch,
decoderand buffer,etc.And toadjustfull
currentoutputrange,you mustdecidetheRset
value(connectedtoIRSET pin)and.Itsvoltage
outputca n beobtained by connect ing
RL1(connectedtoIOUT0 pin)and RL2(connected
toIOUT1 pin),RL3(connectedtoIOUT2 pin)
and RL4(connectedtoIOUT3 pin) Itsmaximum
outputvoltagelimit isCompliance voltage.So
you mustdecidetheRL[4:1],VREFOUTand
Rsetcarefully not toexceedtheoutputvoltage
limit.ItcontainsPDDAC[3:0]pinsfor
power-saveofeachchanneland BGPDfor
power-downmodeofall blocks.Eventhough
oneortwo outof4channelsenterpower-save
mode,thereference block(OPAblock,CMblock,
BGRblock)is still alive,but ifBGPDis
activated(high),thenall blocksofthiscoreis
disableregardless ofPDDAC[3:0],soat thiscase
supplycurrent isalmost justabout thesumof
leakage.You cantchecktheBGR'soutput
voltageby checking theVREFOUTpin.
Theusercan detect thepresence ofanexpected
loadoneachDACoutputby configuring the
DACdigital inputs suchthat thedetection
comparatorthreshold(0.53V)isauseful
thresholdforpresence ofloadresistance.Set
DLDSEL[1:0]toselect the appropriateDAC
output.Transition PREtolow,wait for
settling DTOUTvalue and returnPREbackto
high.
TheIRSET pincreatesa+0.7[V]DCreference
thatcan beforcedwithanexternalreference
voltagepinVREFOUT.Thisvoltagewhen
combinedwiththe externalresistorattachedto
theIRSET pinsetstheoutputcurrentrange
forall quadDACs.Thefollowing example
showshowtocreatea1Vpk-pk outputfora
100 IRENTSCsignal.Any other required
variationscaneasily be calculatedfromthe
suppliedequations.Pleaserememberthat these
areidealequations,themismatchtolerances
fromthedatasheetshould betakeninto
accountforany calculations.
The<figure1>diagramshowsatypical
relationship betweenDACinputand voltage
output.
The<figure2>diagramshowsthebasic
bias-generatorand analog currentswitch.
FromthisdiagramthenumberofDACcodes
fora1Vdeltaoutput is:
C100 =808 -10 =798
1V
808
10
DAC code
Input
An example 10-bit DAC relationship
input code verse output level
<figure 1>
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