SP483EDS/05

SP483E Low EMI Half-Duplex RS485 Transceiver

© Copyright 2000 Sipex Corporation

6

Receivers...

The SP483E receivers have differential inputs

with an input sensitivity as low as

±200mV.

Input impedance of the receivers is typically

15k

Ω (12kΩ minimum). A wide common mode

range of -7V to +12V allows for large ground

potential differences between systems. The

receivers have a tri-state enable control pin.

A logic LOW on RE (pin 2) will enable the

receiver, a logic HIGH on RE (pin 2) will disable

the receiver.

The SP483E receiver is rated for data rates up

to 250 Kbps. The receivers are equipped with

the fail-safe feature. Fail-safe guarantees that

the receiver output will be in a HIGH state when

the input is left unconnected.

Shutdown Mode...

The SP483E is equipped with a Shutdown mode.

To enable the Shutdown state, both the driver

and receiver must be disabled simultaneously. A

logic LOW on DE (pin 3) and a logic HIGH on

RE (pin 2) will put the SP483E into Shutdown

mode. In Shutdown, supply current will drop to

typically 1

µA.

ESD TOLERANCE...

The SP483E device incorporates ruggedized

ESD cells on all driver output and receiver input

pins. The ESD structure is improved over our

previous family for more rugged applications

and environments sensitive to electro-static

discharges and associated transients. The

improved ESD tolerance is at least

±15kV

without damage nor latch-up.

There are different methods of ESD testing

applied:

a) MIL-STD-883, Method 3015.7

b) IEC1000-4-2 Air-Discharge

c) IEC1000-4-2 Direct Contact

DESCRIPTION...

The SP483E is a half-duplex differential

transceiver that meets the requirements of

RS-485 and RS-422. Fabricated with a Sipex

proprietary BiCMOS process, the SP483E

requires a fraction of the power of older bipolar

designs.

The RS-485 standard is ideal for multi-drop

applications and for long-distance interfaces.

RS-485 allows up to 32 drivers and 32 receivers

to be connected to a data bus, making it an ideal

choice for multi-drop applications. Since the

cabling can be as long as 4,000 feet, RS-485

transceivers are equipped with a wide (-7V to

+12V) common mode range to accommodate

ground potential differences. Because RS-485 is

a differential interface, data is virtually immune

to noise in the transmission line.

Drivers...

The driver outputs of the SP483E are differential

outputs meeting the RS-485 and RS-422 stan-

dards. The typical voltage output swing with no

load will be 0 Volts to +5 Volts. With worst case

loading of 54

Ω across the differential outputs,

the drivers can maintain greater than 1.5V volt-

age levels. The drivers have an enable control

line which is active HIGH. A logic HIGH on DE

(pin 3) will enable the differential driver outputs.

A logic LOW on DE (pin 3) will tri-state the

driver outputs.

The SP483E has internally slew rate limited

driver outputs to minimize EMI. The maximum

data rate for the SP483E drivers is 250 Kbps

under load.