RCD16-47B ,RCD NETWORK FOR BUS TERMINATIONAPPLICATIONSIn any electronic equipment where a suitable busterminationis requiredto avoidsignalref ..
RCD1647B6 ,RCD NETWORK FOR BUS TERMINATIONFEATURESFUNCTIONAL DIAGRAMNETWORK OF16R-C-D LINETERMINATIONSRESISTANCE : R = 47 Ω, TOLERANCE +/- 10 ..
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RCD16-47B-RCD1647B6
RCD NETWORK FOR BUS TERMINATION
RCD16-47B
October 1998-Ed:2A
NETWORKOF16R-C-D LINETERMINATIONS
RESISTANCE:R= 47 Ω, TOLERANCE+/- 10%
CAPACITANCE:C =33 pF, TOLERANCE+/-10%
SCHOTTKY DIODE: (D)
FEATURES any electronic equipment wherea suitable bus
terminationis requiredto avoid signal reflectionsand
distortions: and workstation computer
Data-lineanalyzers
MAIN APPLICATIONS
FUNCTIONAL DIAGRAM
DESCRIPTIONWith the increasing speedof data transmission,
line reflections provide signal distorsions and the
overshootsor undershootsproducedon the signal
edges can cause the malfunctionof the whole
system. avoid these negative effects from leadingto
problems,a suitable termination is required.
Dedicatedto bus termination, the RCD16-47B
providesbyfar the best methodto minimise stray
emissions from PCB tracks.
RCD NETWORK
FOR BUS TERMINATION
Application Specific Discretes
A.S.D.TM
Provides impedance matching, thus increasing
noise immunity and minimizing distortion.
LowersEMI/ RFI radiation. DC powerdissipation.
Eliminates negative voltages: no current will
change the biasof the protected device.
Uses the bestof alltermination schemes.
BENEFITSMIL STD 883C- Method3015-6
-VPP=2kV C= 100pF R= 1500Ω3 positivestrikesand3 negativestrikes (F= 1Hz)
COMPLIESWITHTHE FOLLOWINGSTANDARDS:
SO20
SSOP20 47 Ω, tolerance +/− 10 %=33 pF, tolerance+/-10%= Schottky diode
1/7
Withthe increasing speedof datatransmission (PC, TV,...),engineersare naturally confrontedwith effects
that wereof less significance with slower circuits. Among these are the effects describedin transmission
line theory: line reflections provide signal distortionsand the overshootsor undershootsproducedon the
signal edges can finally cause the malfunctionof the whole system.
Reflectionata non terminated lineThe figure below shows the circuitofa transmissionsystemin whicha memory device(inputimpedanceof
100 kΩ)is connectedat the endofa line with line impedance Zo.
APPLICATION NOTE: BUS TERMINATIONΩ
100 kΩ this lineis not properly terminated,a certain amountof the energyis reflected back, inducinga reflection
phenomenathat can distortthe signal.This can resultin improperoperationof the system.
The simulation shownon the above figure illustrates the signal distortion producedby line reflectionat the
endof the line whichis not well terminated.
Evenif thesignalat the startof the line has the correctform(upper curve), considerabledistortion arisesat
theendof the line (lower curve).On the positive edge, the overshoot can exceed the maximum operating
voltageof the used circuittechnologywhich will thenbe destroyed.Also, the following negativeundershoot
mayreacha level low enoughto change the valueof the logic state.Ifit affectsofan addressline,a wrong
memorycell willbe addressed,andin the caseofa data line, the data canbe corrupted.
Thisphenomenaalso occurson the falling edge.
avoid these negative effects from leadingto problemsina system,a suitable terminationis
required.
RCD16-47B2/7
The RCD terminationThe traditional solutionto properly match each lineof the bus consistsof the useof several discrete
resistances, capacitorsand smallschottky diodes. Fora 16-bitbus, this requires48 discrete components.
SGS-THOMSONoffersan innovatingsolution witha monolithic structureusing
ASDTM technology(*).
The
ASDTM technologyenablesto integrate monolithically16 oftheseRCD ”basic cells” ontoa singlechip
device. The
RCD16-47B reduces component cost and assembly cost, saves board space and improves
reliability.
The simulationillustrates the signal distortionproducedby line reflectionat the endof the line when sucha
terminationis used.
The resistor provides the pathterminationfor PCB track, thusresultingin low reflection phenomena.
The capacitorof 33pF blocks DC currents while actingasa short circuit during signal transitions, and
holds the busat the last logic level.It reduces power consumptionand avoids excessive current.
The smallSchottkydiode clamps the negativeremainingundershoots whichcan result from impedance
mismatch. This damps negative voltages and prevents the logic signal from rising above the logic level
’0’ threshold aftera falling edge.
The RCD termination provides optimal solution comparedtoall othertermination techniques.(*) ASD= Apllicaion Specific Discretes.
RCD16-47B3/7
Symbol Parameter and testconditions Typ. Max. Unit Connection resistance (note1) Tamb =25°C 0.25 Ω Total capacitance F=1 MHz,VR= 0V, VRMS =30 mV 45 pF Leakage current VR =VRRM Tj =25°C =70°C Forwardvoltage IF =1 mA =16 mA =25°C =25°C
Note1: Rcis the resistance betweenpin1 and pin11 orbetweenpin10 and pin20
ELECTRICALCHARACTERISTICS
Symbol Parameter Value Unit Total power dissipation per package 500 mW Continuous forward current per Schottkydiode 50 mA
VRRM Repetitive peak reversevoltage 7.5 V
VPP Maximum electrostaticdischarge
MIL STD 883C- METHOD 3015-6
2kV
Tstg
Storage temperature range
Maximum junction temperature55to+ 150
ABSOLUTE MAXIMUM RATINGS (0°C≤ Tamb≤ 70°C)
Symbol Parameter Package Value UnitRth(j-a) Junctionto ambient SO20
SSOP20
140 °C/W
THERMAL RESISTANCE
RCD16-47B4/7
PSPICEMODEL per RCD CELL R1 3Ω R3 9Ω 47Ω 33pF
Cvar
Cvar
Dschot nH SO20
1.75 nH SSOP20
Dschot parameters Cvar parameters magnitudeversus frequency Phase versusfrequency °
SO20 Package
SSOP20 Package magnitudeversus frequency
Phase versusfrequency
RCD16-47B5/7
ORDER CODED 16 -
47 B RLProduct cells R=47Ω
Packaging: tube: tape &reel
package:= SO20= SSOP20
Product Package Base Qty
Tube Tape& reelRCD16-47B SO20 40 1000
RCD16-47B6 SSOP20 66 2000
Type Package MarkingRCD16-47B SO20 RCD1647B
RCD1647B6 SSOP20 RCD1647B6
Packging: Preferredpackagingis tape and reel.
MARKING
RCD16-47B6/7
