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 3.15V. 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.

In RS-485 mode, the transceivers support both the RS-485

and RS-422 differential communication standards. The

RS-485 receiver features full failsafe 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, where

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 (30µA) mode.

The ISL3331 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.

For a dual port version of these devices, please see the

ISL3332/ISL3333 data sheet.

Features

• User Selectable RS-232 or RS-485/RS-422 Interface Port

(Two RS-232 Transceivers or One RS-485/RS-422

Transceiver)

• Operates From a Single 3.3V Supply

• ±15kV (HBM) ESD Protected Bus Pins (RS-232 or

RS-485)

• 5V Tolerant Logic Inputs

• True Flow-Through Pinouts Simplify Board Layouts

• Pb-Free (RoHS Compliant)

• Full Failsafe (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 (ISL3331 Only) . . . . . . . . . . 115kbps

• Fast RS-232 Data Rate . . . . . . . . . . . . . . . Up to 400kbps

• Low Current Shutdown Mode. . . . . . . . . . . . . . . . . . 30µA

• QFN Package Saves Board Space (ISL3331 Only)

• Logic Supply Pin (VL) Eases Operation in Mixed Supply

Systems (ISL3331 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