Datasheet

+3V to +5V, 2500V
RMS
Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
When not actively driving RE, it functions as the fault
indicator (Table 3). A low on RE indicates the part is
functioning properly, while a high indicates a fault is
present. The four causes of a fault indication are:
1) The voltage on V
CC1
is below its undervoltage-lock-
out threshold (2.69V nominal)
2) The voltage on V
CC2
is below its undervoltage-lock-
out threshold (2.80V nominal)
3) There is a problem that prevents the MAX3535E/
MXL1535E from communicating across its isolation
barrier
4) The die temperature exceeds +150°C nominally,
causing the part to go into thermal shutdown
When a fault occurs, RO1 is switched to a logic-high
state if RE is low (Table 3). Open-circuit or short-circuit
conditions on the receiver inputs do not generate fault
conditions; however, any such condition also puts RO1
in a logic-high state (see the
Fail Safe section).
Read RE for fault conditions by using a bidirectional
microcontroller I/O line or a tri-stated buffer as shown in
Figure 10. When using a tri-stated buffer, enable the
driver whenever the voltage on RE needs to be forced
to a logic-high or logic-low. To read RE for a fault con-
dition, disable the driver.
Slew-Rate Control Logic
The SLO input selects between a fast and a slow slew
rate for the driver outputs. Connecting SLO to GND2
selects the slow slew-rate option that minimizes EMI
and reduces reflections caused by improperly terminat-
ed cables at data rates up to 400kbps. This occurs
because lowering the slew rate decreases the rise and
fall times for the signal at the driver outputs, drastically
reducing the high-frequency components and harmon-
ics at the output. Floating SLO or connecting it to V
CC2
selects the fast slew rate, which allows high-speed
operation.
RO1
RE
DE
DI
GND1
RE
OE
FAULT
V
CC1
V
CC1
TRI-STATED BUFFER/
BIDIRECTIONAL MICROCONTROLLER I/O
FAULT
DRIVER OUTPUT BECOMES HIGH IMPEDANCE
FAULT DETECTED
OE
R
MAX3535E
MXL1535E
D
Figure 10. Reading a Fault Condition
MAX3535E/MXL1535E
Maxim Integrated
17