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5
TH7899M
2201A–IMAGE–02/02
HorizontalRegisters
Thesensorhastworeadoutregisterslocatedatthetop(registerA)andatthebottom
(registerB)oftheimagearea.Theycanbedrivenindependentlybytwophaseclocks.
Neverthelesstoallowamultiplechargetransferdirectionfortheusefulpixels(left,right
orhalfleftandhalfright),thetwoclocksaresplitinto6clocks(
Φ
LA
i=1to6
fortheAregis-
terand
Φ
LB
i=1to6
fortheregisterB).Thetransferdirectionisfixedbytheconnection
modeofthesixclocksinto2clocks.
Thedescriptionoftheconnectionwiththetransferdirectionisdescribedin“”onpage9.
Thereadoutregisterhas2072stages,withafurther18extrastagesateachend.What-
everthechosentransferdirectionfortheusefulpixels,the18extrapixels,the7dark
referencesandthe5isolationsarealwaystransferredtothenearestoutputasshownin
thefigurehereunder.
Figure4.
AandBReadoutRegisterStructure
ThereadoutregistercanbedrivenintheMPPmodeifnecessary.
BinnedModes
Twotypesofsummationcanbeperformed:
Verticalsummationineachstageoftheserialregister(AorB)
Horizontalsummationinanoutputsummingwelldrivenby
Φ
Sclockandlocatedat
eachendofthereadoutregisters(AandB).
Nevertheless,onesummationcanbeperformedinboththeregisterandtheoutputsum-
ming,allowinginthisway,tohavearesultingsignalof(2x2)contiguouspixelsfromthe
imagearea.Thus,thesensorisequivalenttoa1024x1024arrayofa28μmx28μm
pixel.Whenusingthebinnedmodewithachargelevel,aftersummation,smallerthan
300ke-(typicalvalue)itisbetter(optimizationofdynamicandlinearity)tokeepthecon-
versionfactorat7μV/e-(with VGL=1VandVDR=13.5V).Butforsummingmodewith
chargelevel,afterbinning,higherthan300ke-,theconversionfactorshouldbereduced
byincreasingtheVGLgateto12VandtheVDRresetdrainto15V.Withsuchamethod,
thesaturationchargeisoptimizedforthebinningmode.
Thissummingtechniqueleadstoanincreasedsignaltonoiseratio,largerpixelsize,
higherframerates(forverticalbinningonly)butattheexpenseofalossinresolution.