PIN FUNCTION
RO 1
R
8
V
CC
Pin 1 – RO – Receiver Output.
Pin 2 – RE – Receiver Output Enable Active LOW.
RE 2
7
B
Pin 3 – DE – Driver Output Enable Active HIGH.
Pin 4 – DI – Driver Input.
Pin 5 – GND – Ground Connection.
DE 3
6
A
D
DI 4
SP485
Top View
5
GND
Pin 6 – A – Driver Output/Receiver Input
Non-inverting.
Pin 7 – B – Driver Output/Receiver Input Inverting.
Pin 8 – V
CC
SP3481/SP3485
Pinout (Top View)
DESCRIPTION
The
SP3481
and the
SP3485
are 2 members
in the family of +3.3V low power half-duplex
transceivers that meet the specifications of the
RS-485 and RS-422 serial protocols. These
devices are pin-to-pin compatible with the Sipex
SP481, SP483, and SP485 devices as well as
popular industry standards. The
SP3481
and
the
SP3485
feature Sipex's BiCMOS process
allowing low power operation without sacrificing
performance.
Drivers
The driver outputs of the
SP3481
and
SP3485
are differential outputs meeting the RS-485 and
RS-422 standards. The typical voltage output
swing with no load will be 0 Volts to +3.3 Volts.
With a load of 54Ω across the differential
outputs, the drivers maintain greater than
1.5V voltage levels. The drivers of the
SP3481
and
SP3485
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 tranceivers in the
SP3481
and
SP3485
operate up to 10Mbps. The 250mA I
SC
maximum limit on the driver output allows
the
SP3481
and the
SP3485
to withstand an
infinite short circuit over the -7.0V to +12.0V
common mode range without catastrophic
damage to the IC.
Receivers
The
SP3481
and
SP3485
receivers have
differential inputs with an input sensitivity as
low as
±200mV.
Input impedance of the
receivers is typically 15kΩ (12kΩ minimum).
A wide common mode range of -7V to +12V
allows for large ground potential differences
between systems. The receivers of the
SP3481
and
SP3485
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 receivers of the
SP3481
and
SP3485
operate
up to 10Mbps. The receiver for each of the three
devices is equipped with fail-safe. Fail-safe
guarantees that the receiver output will be in a
HIGH state when the input is left unconnected.
Shutdown Mode for the SP3481
The
SP3481
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
SP3481
into Shutdown
mode. In Shutdown, supply current will drop to
typical 1µA, 10µA maximum.
10/15/02
SP3481/3485 Low Power Half-Duplex RS485 Transceivers
© Copyright 2000 Sipex Corporation
4
SIPEX [ SIPEX CORPORATION ]
