Datasheet

MAX3380E/MAX3381E
+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.
V
L
Logic Supply Input
Unlike other RS-232 interface devices where the receiv-
er outputs swing between 0 and V
CC
, the MAX3380E/
MAX3381E feature a separate logic supply input (V
L
)
that sets V
OH
for the receiver and INVALID outputs. V
L
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,
1μA 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
V
L
0
V+
V-
V
CC
0
INVALID
OUTPUT
TRANSMITTER
INPUTS
RECEIVER
INPUTS
}
INVALID
REGION
TRANSMITTER
OUTPUTS
t
AUTOSHDN
t
WU
t
WU
t
INVL
t
INVH
t
AUTOSHDN
Figure 4. AutoShutdown Plus/ INVALID Timing Diagram
Figure 3. AutoShutdown Trip Levels