4608X-102-102 Datasheet, PDF (49/62 Pages) Bourns Electronic Solutions – Resistor Networks Product Selection Guide

Bourns Emitter Coupled Logic Terminator 800 Series
Bourns 801, 802, and 804 conformal coated SIP resistor
capacitor networks are designed to terminate 6 transmission
lines using the parallel termination technique. A 0.01 µF capaci-
tor(s) is provided in each network to help maintain a solid Vtt
level within the package, mitigating any potential cross talk or
feedthrough effects. The 804 circuit also contains a 0.1 µF
capacitor for bypassing the Vee supply.
Parallel Termination Technique
R1 and R2 are calculated using the following equations:
R2 = (Vee/Vtt)*Zo
R1 = (R2*Vtt)/(Vee-Vtt)
For a 10K ECL supply voltage of -5.2V and Vtt of -2V:
R2 = 2.6*Zo
R1 = R2/1.6
For a 100K ECL supply voltage of -4.5V and Vtt of -2V:
R2 = 2.25*Zo
R1 = R2/1.25
Thevenin Equivalent Parallel Termination
Parallel termination in ECL applications uses -2.0 volts as the
terminating voltage. This represents a disadvantage since a
separate Vtt power supply must be available (Vee = -5.2 volts,
Vtt = -2.0 volts). For systems in which a separate -2.0 volt sup-
ply is not available, the use of a Thevenin equivalent arrange-
ment, although resulting in higher power consumption, provides
a convenient solution.
Bourns 803 and 805 conformal coated SIP resistor capacitor
networks are designed to terminate 8 transmission lines using
the Thevenin equivalent parallel termination technique. Again, a
0.1 µF capacitor is provided to help maintain a solid Vee level
within the package, mitigating any potential cross talk or
feedthrough effects. The 803 is designed for use with 10K ECL
whereas the 805 is designed for use with 100K ECL.
Thevenin Equivalent Parallel Termination Technique
References:
1. Blood, W.R., MECL System Design Handbook, Motorola,
Inc., 1983.
2. F100K ECL Data Book, Fairchild Semiconductor Corp.,
1986.
3. MECL Device Data, Motorola, Inc., 1987.
4. ECLinPS Data, Motorola, Inc., 1987.
Specifications are subject to change without notice.
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