MAX3085ESA Maxim Integrated Products, MAX3085ESA Datasheet - Page 19

• Manufacturer Part Number: MAX3085ESA
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated Products

Specifications of MAX3085ESA

• Lead Free Status / Rohs Status: No

±15kV ESD-Protected, Fail-Safe, High-Speed (10Mbps),
Figure 20. MAX3083E/MAX3084E/MAX3085E, and MAX3089E
with SRL = V
4000ft of Cable
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus con-
tention. The first, a foldback current limit on the output
stage, provides immediate protection against short cir-
cuits over the whole common-mode voltage range (see
Typical Operating Characteristics ). The second, a ther-
mal shutdown circuit, forces the driver outputs into a
high-impedance state if the die temperature becomes
excessive.
The RS-485/RS-422 standard covers line lengths up to
4000 feet. For line lengths greater than 4000 feet, use
the repeater application shown in Figure 18.
Figures 19, 20, and 21 show the system differential volt-
age for the parts driving 4000 feet of 26AWG twisted-
pair wire at 110kHz into 120Ω loads.
Figure 22. Typical Half-Duplex RS-485 Network
V
A
- V
RO
DI
RO
DE
RE
B
DI
*MAX3089E (HALF-DUPLEX)
CC,
Slew-Rate-Limited RS-485/RS-422 Transceivers
System Differential Voltage at 50kHz Driving
D
MAX3082E
MAX3085E
MAX3088E
______________________________________________________________________________________
R
Line Length vs. Data Rate
Driver Output Protection
2μs/div
B/Z*
A/Y*
120Ω
MAX3080/3089 FIG-19
B
DI
D
5V/div
1V/div
5V/div
A
DE
RO
R
RE
The MAX3082E/MAX3085E/MAX3088E/MAX3089E
transceivers are designed for bidirectional data com-
munications on multipoint bus transmission lines.
Figures 22 and 23 show typical network applications
circuits. These parts can also be used as line repeaters,
with cable lengths longer than 4000 feet, as shown in
Figure 18.
To minimize reflections, the line should be terminated at
both ends in its characteristic impedance, and stub
lengths off the main line should be kept as short as
possible. The slew-rate-limited MAX3082E/MAX3085E,
and the two modes of the MAX3089E, are more tolerant
of imperfect termination.
Figure 21. MAX3086E/MAX3087E/MAX3088E, and MAX3089E
with SRL = GND, System Differential Voltage at 200kHz Driving
4000ft of Cable
V
B
A
DI
- V
RO
DI
D
B
A
DE
RO
120Ω
R
RE
A
B
1μs/div
Typical Applications
R
D
MAX3080/3089 FIG-20
RO
DE
DI
RE
5V/div
1V/div
5V/div
19