1μA Supply-Current, True +3V to +5.5V

The MAX3221/MAX3223/MAX3243 achieve 1μA supply
current with Maxim’s revolutionary AutoShutdown™ feature.
When the MAX3221/MAX3223/MAX3243 do not
sense a valid signal level on their receiver inputs, the
on-board power supply and drivers shut down. This
occurs if the RS-232 cable is disconnected or if the
transmitters of the connected peripheral are turned off.
The system turns on again when a valid level is applied
to any RS-232 receiver input. As a result, the system
saves power without changes to the existing BIOS or
operating system.
The MAX3221/MAX3223/MAX3243 transceivers are 3Vpowered
EIA/TIA-232 and V.28/V.24 communications
interfaces intended for notebook computer applications.
A proprietary, high-efficiency, dual charge-pump
power supply and a low-dropout transmitter combine to
deliver true RS-232 performance from a single +3.0V to
+5.5V supply. A guaranteed data rate of 120kbps provides
compatibility with popular software for communicating
with personal computers.
The MAX3221/MAX3223/MAX3243 require only 0.1μF
capacitors in 3.3V operation, and can operate from input
voltages ranging from +3.0V to +5.5V. They are ideal for
3.3V-only systems, mixed 3.3V and 5.0V systems, or
5.0V-only systems that require true RS-232 performance.
The MAX3221 is a 1-driver/1-receiver 16-pin SSOP version
of the 20-pin MAX3223 (2-driver/2-receiver). The
MAX3243 3-driver/5-receiver, complete serial port is
ideal for notebook or subnotebook computers. The
MAX3243 includes one complementary always-active
receiver. This receiver can monitor an external device
(such as a modem) in shutdown, without forward biasing
the protection diodes in a UART that may have VCC
completely removed.