MAX3292CSD Maxim Integrated Products, MAX3292CSD Datasheet - Page 12

• Manufacturer Part Number: MAX3292CSD
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated Products

Specifications of MAX3292CSD

• Data Rate: 10000 Kbps
• Propagation Delay Time Ns: 44 ns
• Operating Supply Voltage: 5 V
• Supply Current: 2 mA
• Operating Temperature Range: 0 C to + 70 C
• Package / Case: SOIC-14
• Input Voltage: 5 V
• Maximum Power Dissipation: 695 mW
• Mounting Style: SMD/SMT
• Output Current: +/- 30 mA to + 250 mA
• Output Voltage: - 7.5 V to + 12.5 V
• Product: RS-422/RS-485 Combination
• Lead Free Status / Rohs Status: No

When the total amount of time skew becomes 10% or
more of the baud period, the data error rate can
increase sharply.
The standard RS-485 receiver input impedance is 12kΩ
(one unit load), and the standard driver can drive up to
32 unit loads. The MAX3291/MAX3292 transceivers have
a 1/4-unit-load receiver input impedance (48kΩ), allow-
ing up to 128 transceivers to be connected in parallel on
one communication line. Any combination of these
devices and/or other RS-485 transceivers with a total of
32 unit-loads or less can be connected to the line.
Initiate low-power shutdown mode by bringing RE high
and DE low. In shutdown the MAX3291/MAX3292 typi-
cally draw only 1µA of supply current.
Simultaneously driving RE and DE is allowed; the parts
are guaranteed not to enter shutdown if RE is high and
DE is low for less than 80ns. If the inputs are in this
state for at least 300ns, the parts are guaranteed to
enter shutdown.
Enable times t
tics tables correspond to when the part is not in the low-
power shutdown state. Enable times t
t
vers and receivers longer to activate from the low-
power shutdown mode (t
the driver/receiver disable mode (t
RS-485/RS-422 Transceivers with Preemphasis
for High-Speed, Long-Distance Communication
Figure 17. Line-Repeater Application
12
ZL(SHDN)
______________________________________________________________________________________
RO
DE
% Jitter = (total jitter / t
RE
assume the parts are shut down. It takes dri-
DI
ZH
D
R
and t
128 Transceivers on the Bus
Low-Power Shutdown Mode
ZL
ZH(SHDN)
A
B
Z
Y
in the Switching Characteris-
120
120
BAUD
, t
ZH
ZL(SHDN)
, t
MAX3291
MAX3292
)
ZL
·
100
ZH(SHDN)
).
DATA IN
DATA OUT
) than from
and
For line lengths greater than what one MAX3291/
MAX3292 can drive, use the repeater application
shown in Figure 17.
Figure 18 shows the system differential voltage for the
MAX3292 driving 4000 feet of 26AWG twisted-pair wire
into two 120Ω termination loads.
The MAX3291/MAX3292 are targeted for applications
requiring the best combination of long cable length and
lowest bit-error rate. In order to achieve this combina-
tion, the cable system must be set up with care. There
are three basic steps:
1) The cable should only have two ends (no tree configu-
2) Make all branches or stubs short enough so that
Figure 18. MAX3292 System Differential Voltage Driving 4000
Feet, Using Two 120 Ω Termination Resistors
ration with long branches), which are terminated with
a simple resistor termination whose value is the
cable’s characteristic impedance (Z
tions anywhere else along the cable. This ensures that
there are no reflections at the end of the cable, and
that all transmitters (whether they are located at the
ends of the cable or somewhere along the length) see
the same impedance, equal to Z
twice the propagation delay along the stub (down
and back) is significantly less than one baud period
(around 15% or less). This ensures that the reflec-
tions from the end of the stub (which are unavoid-
able, since the stubs are not terminated) settle in
much less than a baud period. If the application
requires a branch much longer than this, use a
repeater (see the Line Repeater section).
RECEIVER
V
INPUT
A
- V
RO
DI
B
TYPICAL OPERATING CIRCUIT, R
2 s/div
PSET
= 1M
Line Termination
O
/ 2.
Line Repeater
O
). Avoid termina-
5V/div
5V/div
1V/div