1 Features

• ESD protection for RS-232 pins

– ±15kV Human-body model (HBM)

– ±8kV IEC 61000-4-2 Contact discharge

– ±15kV IEC 61000-4-2 Air-gap discharge

• Operates with 3V to 5.5V VCC supply

• Operates up to 1Mbit/s

– Low-speed pin-compatible device (250kbit/s) –

TRS3221E

• Available in near chip-scale package, 16-pin VQFN

(RGT, 82% smaller than TSSOP package)

• Low standby current: 1μA typical

• External capacitors : 4 × 0.1μF

• Accepts 5V logic input with 3.3V supply

• Auto-powerdown feature automatically disables

drivers for power savings

2 Applications

• Industrial PCs

• Wired networking

• Data center and enterprise computing

• Battery-powered systems

• PDAs

• Notebooks

• Laptops

• Palmtop PCs

• Hand-held equipment

3 Description

The TRSF3221E consists of one line driver, one

line receiver, and a dual charge-pump circuit

with ±15kV IEC ESD protection pin to pin

(serial-port connection pins, including GND). The

TRSF3221E 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 3V

to 5.5V supply. The TRSF3221E operates at data

signaling rates up to 1Mbit/s and a driver output slew

rate of 24V/μs to 150V/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 TRSF3221E does not sense a valid

RS-232 signal on the receiver input, the driver output

is disabled. If FORCEOFF is set low and the enable

(EN) input is high, both the driver and receiver

are shut off, and the supply current is reduced to

1μA. Disconnecting the serial port or turning off

the peripheral drivers causes the auto-powerdown

condition to occur. Auto-powerdown can be disabled

when FORCEON and FORCEOFF are high. With

auto-powerdown enabled, the device is activated

automatically when a valid signal is applied to the

receiver input. The INVALID output notifies the user

if an RS-232 signal is present at the receiver input.

INVALID is high (valid data) if the receiver input

voltage is greater than 2.7V or less than –2.7V, or

has been between –0.3V and 0.3V for less than 30μs.

INVALID is low (invalid data) if the receiver input

voltage is between –0.3V and 0.3V for more than

30μs. See Figure 6-5 for receiver input levels.