5

Rev. 07/28/04

SP481/483/485 Low Power Half-Duplex RS485 Transceivers

© Copyright 2002 Sipex Corporation

Receivers

SP481, SP483, SP485

The SP481, SP483, and SP485 receivers have

differential inputs with an input sensitivity as

low as

±200mV. Input impedance of the receiv-

ers 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 of the SP481, SP483

and SP485 have a tri-state enable control pin.

A logic LOW on RE (pin 4) will enable the

receiver, a logic HIGH on RE (pin 4) will disable

the receiver.

The receiver for the SP481 and SP485 will

operate up to at least 5Mbps. The SP483 receiver

is rated for data rates up to 250kbps. The receiver

for each of the three devices is 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

and floating.

Shutdown Mode

SP481/SP483

The SP481 and SP483 are 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 5) and

a logic HIGH on RE (pin 4) will put the SP481

or SP483 into Shutdown mode. In Shutdown,

supply current will drop to typically 1

µA.

DESCRIPTION

SP481, SP483, SP485

The SP481, SP483, and SP485 are half-duplex

differential transceivers that meet the require-

ments of RS-485 and RS-422. Fabricated with a

Sipex proprietary BiCMOS process, all three

products require 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

SP481, SP483, SP485

The driver outputs of the SP481, SP483, and

SP485 are differential outputs meeting the RS-

485 and RS-422 standards. 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 voltage levels. The drivers of

the SP481, SP483 and SP485 have an enable

control line which is active HIGH. A logic

HIGH on DE (pin 5) will enable the differential

driver outputs. A logic LOW on DE (pin 5) will

tri-state the driver outputs.

The transmitters of the SP481 and SP485 will

operate up to at least 5Mbps. The SP483 has

internally slew rate limited driver outputs to

minimize EMI. The maximum data rate for the

SP483 driver is 250kbps.