These devices are BiCMOS interface ICs that are user
configured as either a single RS-422, RS-485 differential
transceiver, or as a dual (2 Tx, 2 Rx) RS-232 transceiver.
In RS-232 mode, the on-board charge pump generates RS-232
compliant ±5V Tx output levels, from a supply as low as 4.5V.
Four small 0.1µF capacitors are required for the charge pump.
The transceivers are RS-232 compliant, with the Rx inputs
handling up to 25V, and the Tx outputs handling ±12V.
In RS-485 mode, the transceivers support both the RS-485
and RS-422 differential communication standards. The
RS-485 receiver features "full fail-safe" operation, so the Rx
output remains in a high state if the inputs are open or shorted
together. The RS-485 transmitter supports up to three data
rates, two of which are slew rate limited for problem free
communications. The charge pump disables in RS-485 mode,
thereby saving power, minimizing noise, and eliminating the
charge pump capacitors.
Both RS-232, RS-485 modes feature loopback and shutdown
functions. The loopback mode internally connects the Tx
outputs to the corresponding Rx input, which facilitates the
implementation of board level self test functions. The outputs
remain connected to the loads during loopback, so connection
problems (e.g., shorted connectors or cables) can be detected.
The shutdown mode disables the Tx and Rx outputs, disables
the charge pump if in RS-232 mode, and places the IC in a low
current (35µA) mode.
The ISL41387 is a QFN packaged device that offers additional
functionality, including a lower speed and edge rate option
(115kbps) for EMI sensitive designs, or to allow longer bus
lengths. It also features a logic supply voltage pin (VL) that sets
the VOH level of logic outputs, and the switching points of logic
inputs, to be compatible with another supply voltage in mixed
voltage systems. The QFN's choice of active high or low Rx
enable pins increases design flexibility, allowing Tx/Rx
direction control via a single signal by connecting DEN and
RXEN together.

Features
• 5V powered, user selectable RS-232 or RS-485, RS-422
interface port (two RS-232 transceivers or one RS-485,
RS-422 transceiver)
• ±15kV (HBM) ESD protected bus pins (RS-232 or RS-485)
• True flow-through pinouts simplify board layouts
• Pb-Free (RoHS compliant)
• Large (2.7V) differential VOUT for improved noise immunity
in RS-485, RS-422 networks
• Full fail-safe (open/short) Rx in RS-485, RS-422 mode
• Loopback mode facilitates board self test functions
• User selectable RS-485 data rates . . . . . . . . . . . . . . 20Mbps
- Slew rate limited . . . . . . . . . . . . . . . . . . . . . . . . . . . 460kbps
- Slew rate limited (ISL41387 only) . . . . . . . . . . . . . 115kbps
• Fast RS-232 data rate . . . . . . . . . . . . . . . . . . . . up to 650kbps
• Low current shutdown mode . . . . . . . . . . . . . . . . . . . . . . 35µA
• QFN package saves board space (ISL41387 only)
• Logic supply pin (VL) eases operation in mixed supply
systems (ISL41387 only)

Applications
• Gaming applications (e.g., slot machines)
• Single board computers
• Factory automation
• Security networks
• Industrial/process control networks
• Level translators (e.g., RS-232 to RS-422)
• Point of sale equipment