Datasheet
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DESCRIPTION/ORDERING INFORMATION (CONTINUED)
FUNCTION TABLES
DIN
DOUT
Auto-powerdown
INVALID
RIN
FORCEOFF
FORCEON
ROUT
EN
11
16
9
13
10
8
1
12
MAX3221-EP
3-V TO 5.5-V SINGLE-CHANNEL RS-232 LINE DRIVER/RECEIVER
WITH ± 15-kV ESD PROTECTION
SLLS751 – OCTOBER 2006
Flexible control options for power management are available when the serial port is inactive. The
auto-powerdown 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 enable ( EN) is high, both the driver and receiver are shut off, and the supply
current is reduced to 1 µ A. Disconnecting the serial port or turning off the peripheral drivers causes the
auto-powerdown condition to occur. Auto-powerdown can be disabled when FORCEON and FORCEOFF are
high. With auto-powerdown enabled, the device 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 2.7 V or less than –2.7 V, or has been between
–0.3 V and 0.3 V for less than 30 µ s. INVALID is low (invalid data) if the receiver input voltage is between –0.3 V
and 0.3 V for more than 30 µ s. See Figure 5 for receiver input levels.
EACH DRIVER
(1)
INPUTS
OUTPUT
DRIVER STATUS
VALID RIN
DOUT
DIN FORCEON FORCEOFF
RS-232 LEVEL
X X L X Z Powered off
L H H X H
Normal operation with
auto-powerdown disabled
H H H X L
L L H Yes H
Normal operation with
auto-powerdown enabled
H L H Yes L
L L H No Z
Powered off by auto-powerdown
feature
H L H No Z
(1) H = high level, L = low level, X = irrelevant, Z = high impedance
EACH RECEIVER
(1)
INPUTS
OUTPUT
VALID RIN
ROUT
RIN EN
RS-232 LEVEL
L L X H
H L X L
X H X Z
Open L No H
(1) H = high level, L = low level, X = irrelevant, Z = high impedance
(off), Open = disconnected input or connected driver off
LOGIC DIAGRAM (POSITIVE LOGIC)
2
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