Datasheet
SCBS707E − SEPTEMBER 1997 − REVISED OCTOBER 2003
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
Active bus-hold circuitry is provided to hold unused or floating data inputs at a valid logic level. Use of pullup
or pulldown resistors with the bus-hold circuitry is not recommended.
The B-port outputs, which are designed to source or sink up to 12 mA, include equivalent 22-Ω series resistors
to reduce overshoot and undershoot.
When V
CC
is between 0 and 1.5 V, the devices are in the high-impedance state during power up or power down.
However, to ensure the high-impedance state above 1.5 V, OE
should be tied to V
CC
through a pullup resistor;
the minimum value of the resistor is determined by the current-sinking capability of the driver.
These devices are fully specified for hot-insertion applications using I
off
and power-up 3-state. The I
off
circuitry
disables the outputs, preventing damaging current backflow through the devices when they are powered down.
The power-up 3-state circuitry places the outputs in the high-impedance state during power up and power down,
which prevents driver conflict.
FUNCTION TABLE
INPUTS
OPERATION
OE DIR
OPERATION
L L B data to A bus
L H A data to B bus
H X Isolation
logic diagram (positive logic)
DIR
OE
A1
B1
To Seven Other Channels
1
2
19
18