• RS-232 Bus-Pin ESD Protection Exceeds ±15 kV Using Human-Body Model (HBM)
• Meets or Exceeds the Requirements of TIA/EIA-232-F and ITU v.28 Standards
• Operates With 3-V to 5.5-V V_CC Supply
• Operates up to 250 kbit/s
• One Driver and One Receiver
• Low Standby Current ...1 µA Typical
• External Capacitors ...4 × 0.1 µF
• Accepts 5-V Logic Input With 3.3-V Supply
• Designed to Be Interchangeable With Maxim MAX3221
• Alternative High-Speed Pin-Compatible Device (1 Mbit/s)
  • SNx5C3221
• Auto-Powerdown Feature Automatically Disables Drivers for Power Savings
• Applications
  • Battery-Powered, Hand-Held, and Portable Equipment
  • PDAs and Palmtop PCs
  • Notebooks, Subnotebooks, and Laptops
  • Digital Cameras
  • Mobile Phones and Wireless Devices

The MAX3221 consists of one line driver, one line receiver, 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. The charge pump and four small external capacitors allow operation from a single 3-V to 5.5-V supply. These devices operate 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 on the receiver input, the driver output is disabled. If FORCEOFF\ is set low and EN\ is high, both the driver and receiver 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. With auto-powerdown enabled, the device is activated automatically when a valid signal is applied to the receiver input. The INVALID\ output notifies the user if an RS-232 signal is present at the receiver input. INVALID\ is high (valid data) if the 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 the receiver input voltage is between –0.3 V and 0.3 V for more than 30 µs. Refer to Figure 5 for receiver input levels.