1 Features

• ESD protection for RS-232 bus pins

– ±15-kV Human-body model (HBM)

– ±8-kV IEC61000-4-2, Contact discharge

– ±15-kV IEC61000-4-2, Air-gap discharge

• Operates with single 3-V to 5.5-V VCC supply

• Always-active noninverting receiver output

(ROUT2B)

• Low standby current: 1 μA typical

• External capacitors: 4 × 0.1 μF

• Accepts 5-V logic input with 3.3-V supply

• Serial-mouse driveability

• Supports operation up to 1 Mbit/s

• Auto-powerdown feature to disable driver outputs

when no valid RS-232 signal is sensed

• Available in space-saving RHB (5 mm x 5 mm

QFN-32) package

2 Applications

• Industrial PCs

• Wired networking

• Data center and networking equipment

• Notebooks

• Hand-held equipment

3 Description

The TRSF3243E consists of three line drivers,

five line receivers, and a dual charge-pump circuit

with ±15-kV ESD (HBM and IEC61000-4-2, Air-Gap

Discharge) and ±8-kV ESD (IEC61000-4-2, Contact

Discharge) protection on serial-port connection pins.

This device provides the electrical interface between

an asynchronous communication controller and the

serial-port connector. The charge pump and four small

external capacitors allow operation from a single 3-V

to 5.5-V supply. In addition, this device includes an

always-active noninverting output (ROUT2B), which

allows applications using the ring indicator to transmit

data while the device is powered down. The device

operates at data signaling rates up to 1 Mbit/s and an

increased slew-rate range of 18 V/μs to 150 V/μs.

Flexible control options for power management are

available when the serial port is inactive. The autopowerdown

feature functions when FORCEON is

low and FORCEOFF is high. During this mode of

operation, if the device does not sense a valid

RS-232 signal, the driver outputs are disabled. If

FORCEOFF is set low, both drivers and receivers

(except ROUT2B) are shut off, and the supply current

is reduced to 1 μA. Disconnecting the serial port

or turning off the peripheral drivers causes the autopowerdown

condition to occur.