SP3494EN-L Datasheet, PDF (7/9 Pages) Exar Corporation – Compatibility with the MAX3486 and 75176 Industry Standard Pinout

The SP3494 is a +3.3V low power half-
duplex transceiver that meets the electrical
specifications of the RS-485 and RS-422
serial protocols. This device is pin-to-pin
compatible with the Exar SP3481 and
SP481 devices as well as popular industry
standards such as the MAX3486 and the
75176. The SP3494 feature Exar's BiCMOS
process allowing low power operation without
sacrificing performance. The SP3494 has a
partially slew rate limited driver with a data
transmission rate of 2.5Mbps.
Driver
The driver outputs of the SP3494 are dif-
ferential outputs. The typical voltage output
swing with no load will be 0 volts to V_CC.
With worst case loading of 54Ω across the
differential outputs, the driver can maintain
greater than 1.5V voltage levels.
The SP3494 driver has 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 the DE (pin 3) will
force the driver outputs to high impedance
(high-Z).
The SP3494 driver will operate up to
2.5Mbps. In addition to adhering to the
250mA I_SC maximum limit on the driver out-
put, the driver output short-circuit protection
will allow the device to withstand an infinite
short circuit over the -7.0V to +12V common
mode range without damage.
Receiver
DESCRIPTION
The receiver has differential inputs with an
input sensitivity of ±200mV. Input imped-
ance of the receiver is typically 15kΩ (12kΩ
minimum). A wide common mode range of
-7V to +12V allows for large ground potential
differences between systems. The receiver
is equipped with a fail-safe feature which
guarantees that the receiver output will be
in a high state when the input is left uncon-
nected. The receiver of the SP3494 operate
up to 2.5Mbps.
The receiver of the SP3494 has an enable
control line which is active LOW. A logic LOW
on RE (pin 2) of the SP3494 will enable the
differential receiver. A logic HIGH on RE
(pin 2) will disable the receiver.
The SP3494 is equipped with a shutdown
mode. To enable the shutdown state, both
the driver and receiver must be disable
simultaneously. A logic LOW on DE (pin 3)
and a logic HIGH on RE (pin 2) will put the
SP3494 into shutdown. In shutdown, the
supply current will drop to less than 10µA.
INPUTS
RE DE
Line
DI Condition
X
1
1
No Fault
X
1
0
No Fault
X
0
X
X
Table 1. Transmit Function Truth Table
OUTPUTS
BA
01
10
ZZ
INPUTS
RE
DE
A-B
0
0
+0.2V
0
0
-0.2V
0
0
Inputs Open
1
0
X
Table 2. Receive Function Truth Table
OUTPUTS
R
1
0
1
Z
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

SP3494_100_071012