SN55107A, SN75107A, SN75107B, SN75108A
DUAL LINE RECEIVERS
SLLS069D – JANUARY 1977 – REVISED APRIL 1998
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
basic balanced-line transmission system
The ’107A, SN75107B, and SN75108A dual line devices are designed specifically 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 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; therefore, system performance is not affected by
circulating ground currents.
The unique driver-output circuit allows terminated transmission lines to be driven at normal line impedances.
High-speed system operation is ensured because line reflections are virtually eliminated when terminated lines
are used. Crosstalk is minimized by low signal amplitudes and low line impedances.
The typical data delay in a system is approximately 30 + 1.3 L ns, where L is the distance in feet separating the
driver and receiver. This delay includes one gate delay in both the driver and receiver.
Data is impressed on the balanced-line system by unbalancing the line voltages with the driver output current.
The driven line is selected by appropriate driver-input logic levels. The voltage difference is approximately:
V
DIFF
≈ 1/2I
O(on)
• R
T
High series line resistance causes degradation of the signal. However, the receivers detect signals as low as
25 mV. For normal line resistances, data can be recovered from lines of several thousand feet in length.
Line-termination resistors (R
T
) are required only at the extreme ends of the line. For short lines, termination
resistors at the receiver only may be adequate. The signal amplitude is then approximately:
V
DIFF
≈ I
O(on)
• R
T
Transmission Line Having
Characteristic Impedance Z
O
R
T
= Z
O
/2
L
R
T
R
T
A
B
C
D
Strobes
R
T
R
T
Y
Receiver
‘107A, SN75107B,
SN75108A
Driver
SN55110A, SN75110A,
SN75112
Data Input
Inhibit
Figure 11. Typical Differential Data Line
data-bus or party-line system
The strobe feature of the receivers and the inhibit feature of the drivers allow these dual line devices to be used
in data-bus or party-line systems. In these applications, several drivers and receivers can share a common
transmission line. An enabled driver transmits data to all enabled receivers on the line while other drivers and
receivers are disabled. Data is time multiplexed on the transmission line. The device specifications allow widely
varying thermal and electrical environments at the various driver and receiver locations. The data-bus system
offers maximum performance at minimum cost.
