3 Description
The MAX3221 device consists of one line driver, one
line receiver with dedicated enable pin, and a dual
charge-pump circuit with ±15-kV ESD protection pin
to pin (serial-port connection pins, including GND).
The device meets the requirements of TIA/EIA-232-
F and 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. These devices operate at data
signaling rates up to 250 kbps and a maximum of
30-V/μs driver output slew rate.
Flexible control options for power management
are available when the serial port is inactive.
The automatic power-down 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 on the receiver input, the driver output
is disabled and the supply current is reduced to 1 μA.
The INVALID output notifies the user if an RS-232
signal is present at the receiver input.

1 Features
• RS-232 Bus-pin ESD protection exceeds
±15 kV using human body model (HBM)
• Meets or exceeds the requirements of
TIA/EIA-232-F and ITU V.28 standards
• Operates with 3-V to 5.5-V VCC supply
• Operates up to 250 kbps
• One driver and one receiver
• Low standby current: 1 μA typical
• External capacitors: 4 × 0.1 μF
• Accepts 5-V logic input with 3.3-V supply
• Alternative high-speed pin-compatible
device (1 Mbps)
– SNx5C3221
• Automatic power-down 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