Datasheet

SN54LVTH573, SN74LVTH573
3.3-V ABT OCTAL TRANSPARENT D-TYPE LATCHES
WITH 3-STATE OUTPUTS
SCBS687H − MAY 1997 − REVISED SEPTEMBER 2003
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
These octal latches are designed specifically for low-voltage (3.3-V) V
CC
operation, but with the capability to
provide a TTL interface to a 5-V system environment.
The eight latches of the ’LVTH573 devices are transparent D-type latches. While the latch-enable (LE) input
is high, the Q outputs follow the data (D) inputs. When LE is taken low, the Q outputs are latched at the logic
levels set up at the D inputs.
A buffered output-enable (OE
) input can be used to place the eight outputs in either a normal logic state (high
or low logic levels) or a high-impedance state. In the high-impedance state, the outputs neither load nor drive
the bus lines significantly. The high-impedance state and increased drive provide the capability to drive bus
lines without need for interface or pullup components.
OE
does not affect the internal operations of the latches. Old data can be retained or new data can be entered
while the outputs are in the high-impedance state.
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.
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.
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.
terminal assignments
1234
A 1D OE V
CC
1Q
B 3D 3Q 2D 2Q
C 5D 4D 5Q 4Q
D 7D 7Q 6D 6Q
E GND 8D LE 8Q
FUNCTION TABLE
(each latch)
INPUTS
OUTPUT
OE LE D
OUTPUT
Q
L H H H
L HL L
L LX Q
0
H X X Z
SN74LVTH573 . . . GQN OR ZQN PACKAGE
(TOP VIEW)
1234
A
B
C
D
E