ISL81387, ISL41387

5

FN6201.4

June 9, 2014

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Pin Descriptions

PIN

MODE

FUNCTION

485/232

BOTH

Interface mode select input. High for RS-485 Mode and low for RS-232 Mode.

DEN

BOTH

Driver output enable. The driver outputs, Y and Z, are enabled by bringing DEN high. They are high impedance when DEN is low.

GND

BOTH

Ground connection. This is also the potential of the QFN's thermal exposed pad (EP).

NC

BOTH

No Connection.

ON

BOTH

In RS-232 mode only, ON high enables the charge pumps. ON low, with DEN and RXEN low (and RXEN high if QFN), turns off the

charge pumps (in RS-232 mode), and in either mode places the device in low power shutdown. In both modes, when ON is low,

and DEN is high, and RXEN is high or RXEN is low, loopback is enabled.

RXEN

BOTH

Receiver output enable. Rx is enabled when RXEN is high; Rx is high impedance when RXEN is low and, if using the QFN package,

RXEN is high. When using the QFN and the active high Rx enable function, RXEN should be high or floating.

RXEN

BOTH

Active low receiver output enable. Rx is enabled when RXEN is low; Rx is high impedance when RXEN is high and RXEN is low.

(i.e., to use active low Rx enable function, tie RXEN to GND). For single signal Tx/Rx direction control, connect RXEN to DEN.

Internally pulled high. (QFN only)

BOTH

System power supply input (5V).

BOTH

Logic-Level Supply. All TTL/CMOS inputs and outputs are powered by this supply. (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.

SLEW

RS-485 Slew rate control. With the SLEW pin high, the drivers run at the maximum slew rate (20Mbps). With the SLEW pin low, the drivers

run at a reduced slew rate (460kbps). On the QFN version, works in conjunction with SPB to select one of three RS-485 data

rates. Internally pulled high in RS-485 mode.

SPB

RS-485 Speed control. Works in conjunction with the SLEW pin to select the 20Mbps, 460kbps or 115kbps RS-485 data rate. Internally

pulled high. (QFN only)

RS-232 Receiver output.

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

RS-232 Receiver output.

RS-485 Not used. Output is high impedance, and unaffected by RXEN and 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.

C1+

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

C1-

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

C2+

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

C2-

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

V+

V-