Transceivers with ±15kV ESD Protection

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17

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:

out threshold (2.69V nominal)

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-

selects the fast slew rate, which allows high-speed

operation.

RO1

RE

DE

DI

GND1

RE

OE

FAULT

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