MAX221 MAXIM [Maxim Integrated Products], MAX221 Datasheet - Page 6

• Manufacturer Part Number: MAX221
• Description: +5V, 1uA, Single RS-232 Transceiver with AutoShutdown
• Manufacturer: MAXIM [Maxim Integrated Products]

+5V, 1µA, Single RS-232 Transceiver
with AutoShutdown
Table 1. Output Control Truth Table
X = Don’t care
Figure 2a. Entering 1µA Supply Mode via AutoShutdown
Figure 2b. Transmitter Enabled Using AutoShutdown
6
+0.3V
-0.3V
Shutdown
(Forced Off)
Normal Operation
(Forced On)
Normal Operation
(AutoShutdown)
Shutdown
(AutoShutdown)
RIN
+2.7V
-2.7V
* TRANSMITTER IS DISABLED, REDUCING SUPPLY CURRENT TO 1 A IF
* TRANSMITTER IS ENABLED IF:
_______________________________________________________________________________________
RIN
RECEIVER INPUT IS BETWEEN +0.3V AND -0.3V FOR AT LEAST 30 s.
OPERATION
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 30 s.
STATUS
FORCEON
X
X
1
1
0
0
0
0
COUNTER
COUNTER
30 s
R
30µs
FORCEOFF
R
TO MAX221
POWER SUPPLY
AND TRANSMITTER
0
0
1
1
1
1
1
1
TO MAX221
POWER SUPPLY
INVALID
INVALID
EN
0
1
0
1
0
1
0
1
Table 2. INVALID Truth Table
Figure 2c. AutoShutdown Logic
RS-232 SIGNAL PRESENT
AT RECEIVER INPUT
FORCEOFF
FORCEON
INVALID
INVALID IS AN INTERNALLY GENERATED SIGNAL USED BY
THE 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.
RECEIVER
LEVEL
VALID
Yes
No
Yes
Yes
No
No
X
X
X
X
High-Z
High-Z
High-Z
High-Z
Active
Active
Active
Active
TOUT
INVALID OUTPUT
POWER DOWN
High
Low
High-Z
High-Z
High-Z
High-Z
Active
Active
Active
Active
ROUT