RCD16-47B STMICROELECTRONICS | Alldatasheet
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Technical content
RCD16-47B October 1998 - Ed : 2A NETWORK OF 16R-C-D LINETERMINATIONS RESISTANCE : R = 47 Ω , TOLERANCE +/- 10% CAPACITANCE: C =33 pF,TOLERANCE+/-10% SCHOTTKY DIODE : (D)
FEATURES
In any electronic equipment where a suitable bus terminationis requiredto avoidsignalreflectionsand distortions: PC and workstation computer Data-line analyzers MAIN APPLICATIONS FUNCTIONAL DIAGRAM
DESCRIPTION
With the increasing speed of data transmission, line reflections provide signal distorsions and the overshootsor undershootsproduced on the signal edges can cause the malfunction of the whole system. To avoid these negative effects from leading to problems, a suitable termination is required. Dedicated to bus termination, the RCD16-47B provides by far the best method to 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. Lowers EMI / RFI radiation. No DC power dissipation. Eliminates negative voltages : no current will change the bias of the protected device. Uses the best of all termination schemes. BENEFITS MIL STD 883C - Method 3015-6 PP = 2 kV C= 100 pF R = 1500 Ω - 3 positive strikes and 3 negativestrikes (F= 1Hz) COMPLIESWITH THE FOLLOWINGSTANDARDS: SO20 SSOP20 R=4 7 Ω, tolerance +/− 10 % C = 33 pF, tolerance +/- 10 % D = Schottky diode
With the increasing speedof data transmission (PC, TV, ...), engineersare naturallyconfrontedwith effects that were of less significance with slower circuits. Among these are the effects described in transmission line theory : line reflections provide signal distortions and the overshoots or undershootsproduced on the signal edges can finally cause the malfunction of the whole system. 1. Reflection at a non terminated line The figure below shows the circuit of a transmissionsystem in which a memorydevice (input impedance of 100 kΩ ) is connectedat the end of a line with line impedance Zo. APPLICATION NOTE : BUS TERMINATION 10 Ω 100 kΩ If this line is not properly terminated, a certain amount of the energy is reflected back, inducing a reflection phenomenathat can distortthe signal. This can result in improper operation of the system. The simulation shown on the above figure illustratesthe signal distortion producedby line reflection at the end of the line which is not well terminated. Even if the signal at the start of the line has the correctform(upper curve), considerabledistortion arises at the end of the line (lower curve). On the positive edge, the overshoot can exceed the maximum operating voltageof the used circuit technologywhich will then be destroyed.Also, the following negativeundershoot may reach a level low enough to change the value of the logic state. If it affectsof an addressline, a wrong memorycell will be addressed, and in the case of a data line, the data can be corrupted. This phenomenaalso occurs on the falling edge. To avoid these negative effects from leading to problems in a system, a suitable termination is required. RCD16-47B
- The RCD termination The traditional solution to properly match each line of the bus consists of the use of several discrete resistances, capacitorsand small schottky diodes. For a 16-bit bus, this requires 48 discrete components. SGS-THOMSON offers an innovatingsolution with a monolithic structure usingASD TM technology(*). The ASD TM technologyenables to integrate monolithically16 ofthese RCD ”basic cells” onto a single chip device. TheRCD16-47B reduces component cost and assembly cost, saves board space and improves reliability. The simulation illustrates the signal distortion produced by line reflection at the end of the line when such a termination is used. The resistor provides the path termination for PCB track, thus resulting in low reflection phenomena. The capacitor of 33 pF blocks DC currents while acting as a short circuit during signal transitions, and holds the bus at the last logic level. It reduces power consumption and avoids excessive current. The small Schottkydiode clamps the negative remaining undershoots which can result from impedance mismatch. This damps negative voltages and prevents the logic signal from rising above the logic level ’0’ threshold after a falling edge. The RCD terminationprovides optimal solution compared to all other termination techniques. (*) ASD = Apllicaion Specific Discretes. RCD16-47B
Symbol Parameter and test conditions Typ. Max. Unit R C Connection resistance (note1) Tamb =2 5°C 0.25 Ω C t Total capacitance F = 1 MHz, V R = 0V, VRMS =3 0m V 4 5 p F IR Leakage current V R =V RRM Tj=2 5°C Tj=7 0°C µA VF Forward voltage I F =1m A IF =1 6m A Tj=2 5°C Tj=2 5°C 0.5 V Note 1 : Rc is the resistance between pin 1 and pin 11 or between pin 10 and pin 20
ELECTRICAL CHARACTERISTICS
Symbol Parameter Value Unit P Total power dissipation per package 500 mW IF Continuous forward current per Schottkydiode 50 mA VRRM Repetitive peak reverse voltage 7.5 V VPP Maximum electrostatic discharge MIL STD 883C - METHOD 3015-6 2k V Tstg Tj Storage temperature range Maximum junction temperature - 55 to + 150 150 ABSOLUTE MAXIMUM RATINGS (0°C ≤ Tamb ≤ 70°C) Symbol Parameter Package Value Unit R th(j-a) Junction to ambient SO20 SSOP20 100 140 °C/W THERMAL RESISTANCE RCD16-47B
L R1 3Ω R3 9 Ω R2 47Ω C1 33pF Cvar Cvar Dschot 3 nH SO20 1.75 nH SSOP20 t Dschot parameters Cvar parameters Z magnitudeversus frequency Phase versus frequency Ω ° Ω Z magnitudeversus frequency Phase versus frequency RCD16-47B
16 cells R=4 7 Ω Packaging: : tube RL : tape & reel package : B = SO20 B6 = SSOP20 Product Package Base Qty Tube Tape & reel RCD16-47B SO20 40 1000 RCD16-47B6 SSOP20 66 2000 Type Package Marking RCD16-47B SO20 RCD1647B RCD1647B6 SSOP20 RCD1647B6 Packging : Preferred packagingis tape and reel. MARKING RCD16-47B
SSOP20(Plastic) L Ekb e A 101 D A1 c Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringementof patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written ap- proval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics 1998 STMicroelectronics - Printed in Italy - All rights reserved. STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. http://www.st.com K hx45° CL A A1B e D EH REF. DIMENSIONS Millimeters Inches A 2.00 0.079 A1 0.25 0.010 A2 1.51 2.00 0.059 0.079 c 0.10 0.35 0.004 0.014 D 7.05 8.05 0.278 0.317 E 7.60 8.70 0.299 0.343 e 0.65 0.026 k0 ° 10° 0° 10° PACKAGE MECHANICAL DATA SO20 (Plastic) REF. DIMENSIONS Millimeters Inches A 2.35 2.65 0.092 0.104 A1 0.10 0.20 0.004 0.008 B 0.33 0.51 0.013 0.020 C 0.23 0.32 0.009 0.013 D 12.6 13.0 0.484 0.512 E 7.40 7.60 0.291 0.299 e 1.27 0.050 H 10.0 10.65 0.394 0.419 h 0.25 0.75 0.010 0.029 L 0.50 1.27 0.020 0.050 K8 ° (max) RCD16-47B