Texas Instruments TRS3221E RS-232 Line Driver/Receiver

Flexible control options for power management are available when the serial port is inactive. The auto-power down 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 1µA. Disconnecting the serial port or turning off the peripheral drivers causes the auto-power down condition to occur. Auto-power down can be disabled when FORCEON and FORCEOFF are high.

With auto-power down enabled, the Texas Instruments TRS3221E 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 2.7V or less than –2.7V, or has been between –0.3V and 0.3V for less than 30µs. INVALID is low (invalid data) if the receiver input voltage is between –0.3V and 0.3V for more than 30µs.