DS75108M NSC [National Semiconductor], DS75108M Datasheet - Page 5

• Manufacturer Part Number: DS75108M
• Description: Dual Line Receivers
• Manufacturer: NSC [National Semiconductor]

Typical Applications
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
The typical data delay in a system is approximately (30
1 3L) 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
High series line resistance will cause degradation of the sig-
nal The receivers however will detect signals as low as
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Data-Bus or Party-Line System
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25 mV (or less) For normal line resistances data may be
recovered from lines of several thousand feet in length
Line termination resistors (R
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
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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