Data-Bus or Party-Line System

TLF9446 – 3

APPLICATION

The DS55107 DS75107 dual line circuits are designed spe-

cifically for use in high speed data transmission systems

that utilize balanced terminated transmission lines such as

twisted-pair lines The system operates in the balanced

mode so that noise induced on one line is also induced on

the other The noise appears common mode at the receiver

input terminals where it is rejected The ground connection

between the line driver and receiver is not part of the signal

circuit so that system performance is not affected by circu-

lating ground currents

The unique driver output circuit allows terminated transmis-

sion lines to be driven at normal line impedances High

speed system operation is ensured since line reflections are

virtually eliminated when terminated lines are used Cross-

talk is minimized by low signal amplitudes and low line im-

pedances

13L) ns where L is the distance in feet separating the driv-

er and receiver This delay includes one gate delay in both

the driver and receiver

Data is impressed on the balanced-line system by unbalanc-

ing the line voltages with the driver output current The driv-

en line is selected by appropriate driver input logic levels

The voltage difference is approximately

(1)

High series line resistance will cause degradation of the sig-

nal The receivers however will detect signals as low as

25 mV (or less) For normal line resistances data may be

recovered from lines of several thousand feet in length

treme ends of the line For short lines termination resistors

at the receiver only may prove adequate The signal ampli-

tude will then be approximately

(2)

The strobe feature of the receivers and the inhibit feature of

the drivers allow the DS55107 DS75107 dual line circuits to

be used in data-bus or party-line systems In these applica-

tions several drivers and receivers may share a common

transmission line An enabled driver transmits data to all

enabled receivers on the line while other drivers and receiv-

ers are disabled Data is thus time multiplexed on the trans-

mission line The DS55107 DS75107 device specifications

allow widely varying thermal and electrical environments at

the various driver and receiver locations The data-bus sys-

tem offers maximum performance at minimum cost

The DS55107 DS75107 dual line circuits may also be used

in unbalanced or single line systems Although these sys-

tems do not offer the same performance as balanced sys-

tems for long lines they are adequate for very short lines

where environment noise is not severe

The receiver threshold level is established by applying a DC

reference voltage to one receiver input terminal The signal

from the transmission line is applied to the remaining input

The reference voltage should be optimized so that signal

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