Datasheet
MAX221E
±15kV ESD-Protected, +5V, 1µA, Single RS-232
Transceiver with AutoShutdown
6 _______________________________________________________________________________________
1 No
Shutdown
(AutoShutdown)
High-Z1 High-Z0
1
1
1
OPERATION
STATUS
X0
VALID
RECEIVER
EN
X
Shutdown
(Forced Off)
X
Normal Operation
(Forced On)
X0
Yes
Normal Operation
(AutoShutdown)
No
Yes0
0
High-Z
Active
Active
High-Z
TOUT
Active
High-Z
Active
0
FORCEOFF
1
0
1
1
1
1
High-Z
High-Z
Active
Active
ROUT
High-Z
Active
Active
X
FORCEON
1
X
1
0
0
0
RS-232 SIGNAL PRESENT
AT RECEIVER INPUT
INVALID OUTPUT
Yes High
No Low
Table 1. Output Control Truth Table
Table 2. INVALID Truth Table
Figure 2c. AutoShutdown Logic
+0.3V
-0.3V
INVALID
TO MAX221E
POWER SUPPLY
AND TRANSMITTER
RIN
* TRANSMITTER IS DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
RECEIVER INPUT IS BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
30µs
COUNTER
R
+2.7V
-2.7V
INVALID
TO MAX221E
POWER SUPPLY
RIN
* TRANSMITTER IS ENABLED IF:
RECEIVER INPUT IS GREATER THAN +2.7V OR LESS THAN -2.7V.
RECEIVER INPUT HAS BEEN BETWEEN +0.3V AND -0.3V FOR LESS THAN 30µs.
30µs
COUNTER
R
FORCEOFF
POWER DOWN
INVALID
FORCEON
INVALID IS AN INTERNALLY GENERATED SIGNAL USED BY
AUTOSHUTDOWN LOGIC AND APPEARS AS AN OUTPUT.
POWER DOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE
OPERATIONAL STATUS OF THE TRANSMITTER AND POWER SUPPLIES.
Figure 2b. Transmitter Enabled Using AutoShutdown
Figure 2a. Entering 1µA Supply Mode via AutoShutdown
x = Don’t care