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.