XR5486E Datasheet, PDF (14/23 Pages) Exar Corporation – ULTRA HIGH SPEED RS-485/RS-422 PROFIBUS TRANSCEIVERS WITH 1/8TH UNIT LOAD AND 15KV ESD-PROTECTION

XR5486E-5488E
ULTRA HIGH SPEED RS-485/RS-422 PROFIBUS TRANSCEIVERS WITH 1/8TH UNIT LOAD AND +/-15KV ESD-PROTECTION
REV. 1.0.0
1.0 PRODUCT DESCRIPTION
XR5486E-XR5488E is a family of advanced RS-485/RS-422 transceivers. Each contain one driver and one
receiver. The XR5488E is a half-duplex design while the XR5486E and XR5487E are full-duplex designs. All
devices operate from a single 5.0V power supply. These devices feature failsafe circuitry that guarantees a
logic-high receiver output when the inputs are open or shorted, or when they are connected to a terminated
transmission line with all drivers disabled. The control pins RE and DE feature a hotswap capability allowing
live insertion without spurious data transfer. The drivers are not slew rate limited making transmit speeds up to
52Mbps possible. Drivers are output short-circuit current limited. Thermal-shutdown circuitry protects drivers
against excessive power dissipation. When activited, the thermal-shutdown circuitry forces the driver outptus
into a high-impedance state.
ADVANCED FAILSAFE
Ordinary RS-485 differential receivers will be in an indeterminate state whenever the data bus is not being
actively driven. The Advanced Failsafe feature of the XR5486E-XR5488E family guarantees a logic-high
receiver output when the receiver inputs are open or shorted, or when they are connected to a terminated
transmission line with all drivers disabled. In a terminated bus with all transmitters disabled, the receivers’
differential input voltage is pulled to 0V by the termination. The XR5486E-XR5488E family interprets 0V
differential as a logic high with a minimum 50mV noise margin while maintaining compliance with the EIA/TIA-
485 standard of +/-200mV.
HOT-SWAP CAPABILITY
When a micro-processor or other logic device undergoes its power-up sequence, its logic-outputs are typically
at high impedance. In this state they are unable to drive the DE and RE signals to a defined logic level. During
this period, noise, parasitic coupling or leakage from other devices could cause standard CMOS enable inputs
to drift to an incorrect logic level.
If circuit boards are inserted into an energized backplane (commonly called "live insertion" or "hot-swap")
power may suddenly be applied to all circuits. Without the hot-swap capability, this situation could improperly
enable the transceiver’s driver or receiver, driving invalid data onto shared busses and possibly causing driver
contention or device damage.
The XR5486E-XR5488E family contains a special power-on-reset circuit that holds the driver enable and
receiver enable inactive for approximately 10 microseconds. After this initial power-up sequence the hot-swap
circuit becomes transparent and driver enable and receiver enable resume their normal un-skewed functions
and timings.
+/-15kV ESD PROTECTION
ESD protection structures are incorporated on all pins to protect against electrostatic discharges encountered
during handling and assembly. The driver outputs and receiver inputs of the XR5486E-XR5488E family have
extra protection against static electricity. Exar uses state of the art structures to protect these pins against ESD
of +/-15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown
and powered down. After an ESD event, the XR5486E-XR5488E family keep operating without latch-up or
damage.
ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the XR5486E-
XR5488E family are characterized for protection to the following limits:
■ +/-15kV using the Human Body Model
■ +/-8kV using the Contact Discharge Model
■ +/-15kV using the Airgap Discharge Model
ESD TEST CONDITIONS
ESD performance depends on a variety of conditions. Contact Exar for a reliability report that documents test
setup, methodology and results.
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