DESCRIPTION
The
SP3493/3494
are +3.3V transceivers that
meet the electrical specifications of the
RS-485 and RS-422 serial protocols. The
SP3493/3494
feature Sipex's BiCMOS process
allowing low power operation without
sacrificing performance.
The
SP3493
device is a +3.3V full-duplex
transceiver that is pin-to-pin compatible with
the
Sipex SP3490
and
SP490
devices as well as
popular industry standards such as the
MAX3488, the LTC490, and the 75179. The
SP3493
has a driver with a data transmission
rate of 250kbps.
The
SP3494
device is a +3.3V half-duplex
transceiver that is pin-to-pin compatible with
the
Sipex SP3481
and
SP481
devices as well as
popular industry standards such as the MAX3486
and the 75176. The
SP3494
has a partially slew-
rate limited driver with a data transmission rate
of 2.5Mbps.
Drivers
The
SP3493/3494devices
both have differential
outputs. The typical voltage output swing with
no load will bo 0V 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
device 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 DE (pin 3) will force the driver
outputs at high impedance (high-Z). The
SP3493
device does not have a driver enable.
The
SP3493/SP3494
drivers will operate up to
250kbps and 2.5Mbps, respectively. In addition
to adhering to the 250mA I
SC
maximum limit on
the driver output, the driver output short-circuit
protection will allow the devices to withstand an
infinite short circuit over the -7.0V to +12V
common mode range without damage.
Receivers
The receivers have differential inputs with an
input sensitivity as low +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.
Both the
SP3493/SP3494
receivers are
equipped with fail-safe which guarantees that
the receiver outputs will be in a high state
when the input is left unconnected.
The
SP3494
receiver has a high impedance
(high-Z) 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
SP3494
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
SP3494
into shutdown.
In shutdown, the supply current will drop to 2nA
typical, 1µA maximum.
10/16/02
SP3493/3494 +3.3V Low Power Slew-Rate Limited RS-485/RS-422 Transceivers
© Copyright 2002 Sipex Corporation
6
SIPEX [ SIPEX CORPORATION ]
