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, Contact Discharge) 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-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/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 than 30 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
• Operates With 3-V to 5.5-V VCC Supply
• Always-Active Noninverting Receiver Output (ROUT2B)
• Designed to Transmit at a Data Rate up to500 kbit/s
• Low Standby Current . . . 1 µA Typ
• External Capacitors . . . 4 × 0.1 µF
• Accepts 5-V Logic Input With 3.3-V Supply
• Designed to Be Interchangeable With Maxim MAX3243E
• Serial-Mouse Driveability
• Auto-Powerdown Feature to Disable Driver Outputs When No Valid RS-232 Signal Is Sensed
• Package Options Include Plastic Small-Outline (DW), Shrink Small-Outline (DB), and Thin Shrink Small-Outline (PW) Packages