The MAX3243E device consists of three line drivers, five line receivers, and a dual charge-pump circuit with ±15-kV ESD (HBM and IEC61000-4-2, Air-Gap Discharge) and ±8-kV ESD (IEC61000-4-2, ContactDischarge) protection on serial-port connection pins. The device meets the requirements of TIA/EIA-232-F and provides the electrical interface between an asynchronous communication controller and the serial-portconnector. 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 applicationsusing 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/µs 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 µA. 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, and should be done when driving a serial mouse. With auto-powerdown enabled, the device is activated automatically when a valid signal is applied to any receiver input. The INVALID\ output is used to notify the user if an RS-232 signal is present at any receiver input. INVALID\ is high (valid data) if any receiver input voltage is greater than 2.7 V or less than –2.7 V or has been between –0.3 V and 0.3 V for less than30 µs. INVALID\ is low (invalid data) if all receiver input voltages are between –0.3 V and 0.3 V for more than 30 µs. Refer to Figure 5 for receiver input levels.
The MAX3243EC is characterized for operation from 0°C to 70°C. The MAX3243EI is characterized for operation from –40°C to 85°C.
Single-Chip and Single-Supply Interface for IBM PC/AT Serial Port
ESD Protection for RS-232 Bus Pins
±15-kV Human-Body Model (HBM)
±8-kV IEC61000-4-2, Contact Discharge
±15-kV IEC61000-4-2, Air-Gap Discharge
Meets or Exceeds Requirements of TIA/EIA-232-F and ITU v.28 Standards