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.