+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

_______________________________________________________________________________________

9

By connecting FORCEON and FORCEOFF to INVALID,

the MAX3380E/MAX3381E are shut down when no valid

receiver level is detected.

Unlike other RS-232 interface devices where the receiv-

also sets the threshold for the transmitter inputs,

FORCEON and FORCEOFF. This feature allows a great

deal of flexibility in interfacing to many different types of

systems with different logic levels. Connect this input to

+2.7V

+0.3V

0

-0.3V

-2.7V

TRANSMITTERS ENABLED, INVALID HIGH

INDETERMINATE

AutoShutdown, TRANSMITTERS DISABLED,

1

µA SUPPLY CURRENT INVALID LOW

INDETERMINATE

TRANSMITTERS ENABLED, INVALID HIGH

POWERDOWN*

AUTOSHDN

FORCEOFF

FORCEON

* POWERDOWN IS ONLY AN INTERNAL SIGNAL.

IT CONTROLS THE OPERATIONAL STATUS OF

THE TRANSMITTERS AND THE POWER SUPPLIES.

Figure 2d. Power-Down Logic

AUTOSHDN

R_IN

T_IN

R

S

30s

TIMER

EDGE

DETECT

EDGE

DETECT

FORCEOFF

FORCEON

Figure 2c. AutoShutdown Plus Logic

0

V+

V-

0

INVALID

OUTPUT

TRANSMITTER

INPUTS

RECEIVER

INPUTS

}

INVALID

REGION

TRANSMITTER

OUTPUTS

Figure 4. AutoShutdown Plus/INVALID Timing Diagram

Figure 3. AutoShutdown Trip Levels