5

FN6362.0

May 27, 2008

Pin Descriptions

PIN

MODE

FUNCTION

GND

BOTH

Ground connection.

LB

BOTH

Enables loopback mode when low. Internally pulled-high.

NC

BOTH

No Connection.

ON/OFF

BOTH

If either port is in RS-232 mode, a low on ON/OFF disables the charge pumps. In either mode, a low disables all the outputs,

and places the device in low power shutdown. Internally pulled-high. ON = 1 for normal operation.

RXEN

BOTH

Active low receiver output enable. The corresponding port’s Rx is enabled when RXEN is low; Rx is high impedance when

RXEN is high. Internally pulled low. (QFN only)

SEL

BOTH

Interface Mode Select input. High puts corresponding port in RS-485 Mode, while a low puts it in RS-232 Mode.

BOTH

System power supply input (3.3V).

BOTH

Logic-Level Supply. All TTL/CMOS inputs and outputs are powered by this supply. QFN logic input pins that are externally

DEN

RS-232 Active high driver output enable. The corresponding port’s 232 mode drivers are enabled when DEN is high; drivers are

disabled when DEN is low. Internally pulled high. (QFN only).

A

RS-232 Receiver input with

RS-485 Inverting receiver input with

±15kV ESD protection.

B

RS-232 Receiver input with

RS-485 Noninverting receiver input with

±15kV ESD protection.

RS-485 Driver output enable (DE). The driver outputs, Y and Z, are enabled by bringing DE high. They are high impedance when

DE is low. Internally pulled high when port selected for RS-485 mode.

RS-232 Receiver output.

unconnected (floating) or shorted together (i.e., full fail-safe).

RS-232 Receiver output.

RS-485 Not used. Internally pulled-high, and unaffected by RXEN.

Y

RS-232 Driver output with

±15kV ESD protection.

RS-485 Inverting driver output with

±15kV ESD protection.

Z

RS-232 Driver output with

±15kV ESD protection.

RS-485 Noninverting driver output with

±15kV ESD protection.

SP

RS-485 Speed control. Internally pulled-high. (QFN only)

C1+

RS-232 External capacitor (voltage doubler) is connected to this lead. Not needed if both ports in RS-485 Mode.

C1-

RS-232 External capacitor (voltage doubler) is connected to this lead. Not needed if both ports in RS-485 Mode.

C2+

RS-232 External capacitor (voltage inverter) is connected to this lead. Not needed if both ports in RS-485 Mode.

C2-

RS-232 External capacitor (voltage inverter) is connected to this lead. Not needed if both ports in RS-485 Mode.

V+

RS-232 Internally generated positive RS-232 transmitter supply (+5.5V). C3 not needed if both ports in RS-485 Mode.

V-

RS-232 Internally generated negative RS-232 transmitter supply (-5.5V). C4 not needed if both ports in RS-485 Mode.

ISL3332, ISL3333