MAX3082 MAXIM [Maxim Integrated Products], MAX3082 Datasheet - Page 18

• Manufacturer Part Number: MAX3082
• Description: Fail-Safe, High-Speed 10Mbps, Slew-Rate-Limited RS-485/RS-422 Transceivers
• Manufacturer: MAXIM [Maxim Integrated Products]

Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the devices typically
draw only 1nA of supply current.
RE and DE may be driven simultaneously; the parts are
guaranteed not to enter shutdown if RE is high and DE
is low for less than 50ns. If the inputs are in this state
for at least 600ns, the parts are guaranteed to enter
shutdown.
Enable times t
acteristics tables assume the part was not in a low-
power shutdown state. Enable times t
t
drivers and receivers longer to become enabled from
low-power shutdown mode (t
from driver/receiver-disable mode (t
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.
Fail-Safe, High-Speed (10Mbps),
Slew-Rate-Limited RS-485/RS-422 Transceivers
18
Figure 17. Line Repeater for MAX3080/MAX3081/
MAX3083/MAX3084/MAX3086/MAX3087, and MAX3089
in Full-Duplex Mode
ZL(SHDN)
NOTE: RE AND DE ON MAX3080/MAX3083/MAX3086/MAX3089 ONLY.
______________________________________________________________________________________
(except MAX3082/MAX3085/MAX3088)
RO
DE
RE
assume the parts were shut down. It takes
DI
ZH
D
R
Low-Power Shutdown Mode
and t
Driver Output Protection
ZL
A
B
Z
Y
ZH(SHDN)
in the Switching Char-
120
120
MAX3080/MAX3081/MAX3083/
MAX3084/MAX3086/MAX3087/
MAX3089 (FULL DUPLEX)
ZH
, t
, t
ZL
ZH(SHDN)
ZH(SHDN)
).
DATA IN
DATA OUT
) than
and
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 17.
Figures 18, 19, and 20 show the system differential volt-
age for the parts driving 4000 feet of 26AWG twisted-
pair wire at 110kHz into 120 loads.
The MAX3082/MAX3085/MAX3088/MAX3089 trans-
ceivers are designed for bidirectional data communica-
tions on multipoint bus transmission lines. Figures 21
and 22 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 17.
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 MAX3082/MAX3085,
and the two modes of the MAX3089, are more tolerant
of imperfect termination.
Figure 18. MAX3080/MAX3081/MAX3082, and MAX3089
with SRL = Unconnected, System Differential Voltage at 50kHz
Driving 4000 feet of Cable
V
A
- V
RO
DI
B
Line Length vs. Data Rate
5 s/div
Typical Applications
MAX3080/3089 FIG-18
5V/div
1V/div
5V/div