Datasheet
SCDS139 − OCTOBER 2003
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
The SN74CBT16245C is a high-speed TTL-compatible FET bus switch with low ON-state resistance (r
on
),
allowing for minimal propagation delay. Active Undershoot-Protection Circuitry on the A and B ports of the
SN74CBT16245C provides protection for undershoot up to −2 V by sensing an undershoot event and ensuring
that the switch remains in the proper OFF state.
The SN74CBT16245C is organized as two 8-bit bus switches with separate output-enable (1OE
, 2OE) inputs.
It can be used as two 8-bit bus switches or as one 16-bit bus switch. When OE
is low, the associated 8-bit bus
switch is ON, and the A port is connected to the B port, allowing bidirectional data flow between ports. When
OE
is high, the associated 8-bit bus switch is OFF and the high-impedance state exists between the A and B
ports.
This device is fully specified for partial-power-down applications using I
off
. The I
off
feature ensures that
damaging current will not backflow through the device when it is powered down. The device has isolation during
power off.
To ensure the high-impedance state during power up or power down, 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.
FUNCTION TABLE
(each 8-bit bus switch)
INPUT
INPUT/OUTPUT
FUNCTION
INPUT
OE
INPUT/OUTPUT
A
FUNCTION
L B A port = B port
H Z Disconnect
logic diagram (positive logic)
1A1
SW
1B1
1A8
1OE
SW
1B8
2A1
SW
2B1
2A8
2OE
SW
2B8
47
37
48
36
26
25
2
12
13
23