34
TSPC750A/740A
2128A–HIREL–01/02
Figure22.
DriverImpedanceMeasurement
Table18summarizesthesignalimpedanceresults.Thedriverimpedancevalueswere
derivedbysimulationat65
°
C.Astheprocessvaries,theoutputimpedancewillbe
reducedbyseveralohms.
Pull-upResistor
Requirements
TheTSPC750Arequireshigh-resistive(weak:10K
)pull-upresistorsonseveralcontrol
signalsofthebusinterfacetomaintainthecontrolsignalsinthenegatedstateafterthey
havebeenactivelynegatedandreleasedbytheTSPC750Aorotherbusmasters.
ThesesignalsareTS,ABB,DBB,andARTRY.
Inaddition,theTSPC750Ahasoneopen-drainstyleoutputthatrequiresapull-upresis-
tors(weakorstronger:4.7K
-10K
)ifitisusedbythesystem.Thissignalis
CKSTP_OUT.
Duringinactiveperiodsonthebus,theaddressandtransferattributesonthebusare
notdrivenbyanymasterandmayfloatinthehigh-impedancestateforrelativelylong
periodsoftime.SincetheTSPC750Amustcontinuallymonitorthesesignalsforsnoop-
ing,thisfloatconditionmaycauseexcessivepowerdrawbytheinputreceiversonthe
TSPC750Aorbyotherreceiversinthesystem.Itisrecommendedthatthesesignalsbe
pulledupthroughweak(10K
)pull-upresistorsorrestoredinsomemannerbythesys-
tem.ThesnoopedaddressandtransferattributeinputsareA[0-31],AP[0-3],TT[0-4],
TBST,andGBL.
Table18.
ImpedanceCharacteristics
V
DD
=2.6V,OV
DD
=3.3V,Tj=65
°
C
Process
60x
L2
Symbol
Unit
TYP
43
38
Z
0
Ohms
OVDD
OGND
RP
RN
Pad
Data
SW2
SW1