The MAX3243 consists of three line drivers, five line receivers, and a dual charge-pump circuit with ±15-kV ESD (HBM) 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.

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.

• Controlled Baseline
  • One Assembly/Test Site, One Fabrication Site
• Extended Temperature Performance of -55°C to 125°C
• Enhanced Diminishing Manufacturing Sources (DMS) Support
• Enhanced Product-Change Notification
• Qualification Pedigree(1)
• Single-Chip and Single-Supply Interface for IBM PC/AT™ Serial Port
• RS-232 Bus-Pin ESD Protection Exceeds ±15 kV Using Human-Body Model (HBM)
• D 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
• Three Drivers and Five Receivers
• Low Standby Current . . . 1 mA Typical
• External Capacitors . . . 4 × 0.1 mF
• Accepts 5-V Logic Input With 3.3-V Supply
• Always-Active Noninverting Receiver Output (ROUT2B)
• Serial-Mouse Driveability
• Auto-Powerdown Feature to Disable Driver Outputs When No Valid RS-232 Signal Is Sensed
• Applications
  • Battery-Powered Systems, PDAs, Notebooks, Laptops, Palmtop PCs, and Hand-Held Equipment

(1)Component qualification in accordance with JEDEC and industry standards to ensure reliable operation over an extended temperature range. This includes, but is not limited to, Highly Accelerated Stress Test (HAST) or biased 85/85, temperature cycle, autoclave or unbiased HAST, electromigration, bond intermetallic life, and mold compound life. Such qualification testing should not be viewed as justifying use of this component beyond specified performance and environmental limits. IBM, PC/AT are trademarks of IBM.