The MAX3243 device consists of three line drivers, five line receivers, 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. This combination of drivers and receivers matches that needed for the
typical serial port used in an IBM PC/AT, or compatible. The charge pump and four small external capacitors
allow operation from a single 3-V to 5.5-V supply. In addition, the 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 250 kbit/s and a maximum of 30-V/ms driver output slew
rate.
Flexible control options for power management are available when the serial port is inactive. The
auto-powerdown 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 mA.
Disconnecting the serial port or turning off the peripheral drivers causes the auto-powerdown condition to occur.