Datasheet


      
 ±  

SLLS409K − JANUARY 2000 − REVISED MARCH 2004
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
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, the driver outputs are disabled. If FORCEOFF
is set low and EN is high, both drivers and receivers are shut off, and the supply current is reduced to 1 µA.
Disconnecting the serial port or turning off the peripheral drivers causes auto-powerdown 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 any receiver input. The INVALID
output
is used to notify the user if an RS-232 signal is present at any receiver input. INVALID
is high (valid data) if any
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 µs. INVALID
is low (invalid data) if the receiver input voltage is between −0.3 V and 0.3 V for more than
30 µs. Refer to Figure 4 for receiver input levels.
Function Tables
EACH DRIVER
INPUTS
OUTPUT
DIN FORCEON
FORCEOFF
VALID RIN
RS-232 LEVEL
OUTPUT
DOUT
DRIVER STATUS
X X L X Z Powered off
L H H X H
Normal operation with
H HH XL
Normal operation with
auto-powerdown disabled
L L H Yes H
Normal operation with
H LH YesL
Normal operation with
auto-powerdown enabled
L L H No Z
Powered off by
H L H No Z
Powered off by
auto-powerdown feature
H = high level, L = low level, X = irrelevant, Z = high impedance
EACH RECEIVER
INPUTS
OUTPUT
RIN
EN
VALID RIN
RS-232 LEVEL
OUTPUT
ROUT
L L X H
H LX L
X HX Z
Open L No H
H = high level, L = low level, X = irrelevant,
Z = high impedance (off), Open = input
disconnected or connected driver off