MC75172BDW ON Semiconductor, MC75172BDW Datasheet - Page 10

• Manufacturer Part Number: MC75172BDW
• Description: Bus Transmitters Quad EIA-485 Line
• Manufacturer: ON Semiconductor

Specifications of MC75172BDW

• Data Rate: 10 Mbps
• Interface: EIA/TIA-422-A, EIA/TIA-485, V.11, V.27
• Supply Voltage (max): 5.25 V
• Supply Voltage (min): 4.75 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-20 Wide
• Minimum Operating Temperature: - 40 C
• Lead Free Status / Rohs Status: No RoHS Version Available

Termination Resistors
the shape and integrity of a waveform traveling along a
cable, the cable must be terminated in an impedance equal
to its characteristic impedance. In a system such as that
depicted in Figure 18, in which data can travel in both
directions, both physical ends of the cable must be
terminated. Stubs, leading to each receiver and driver,
should be as short as possible.
TTL
Transmission line theory states that, in order to preserve
TTL
NOTES:
TTL
5 “off” drivers (@ 0.06 U.L. each),
+8 receivers (@ 1.0 U.L. each) = 8.3 Unit Loads
R
D
#8
T
= 120 W at each end of the cable.
En
1.Terminating resistors R
2.Stubs should be as short as possible.
3.Circuit ground of all drivers and receivers must be connected via a dedicated wire within the cable.
#6
R
Do not rely on chassis ground or power line ground.
D
#1
En
R
T
R
T
T
must be located at the physical ends of the cable.
R
Figure 18. Typical EIA−485 System
#7
R
MC75172B, MC75174B
#1
R
TTL
http://onsemi.com
#6
TTL
TTL
10
TTL
R
reflections which can have amplitudes of several volts
above V
undershoots can disrupt the driver and/or receiver
operation, create false data, and in some cases damage
components on the bus.
R
#2
Leaving off the terminations will generally result in
#5
D
En
#2
CC
TTL
TTL
or below ground. These overshoots and
TTL
TTL
TTL
TTL
TTL
#3
#4
D
D
D
#3
R
R
#5
En
En
En
#4
Twisted
120 W
Pair