74ACT11478

METASTABLERESISTAND OCTAL DTYPE DUALRANK FLIPFLOP

WITH 3-STATE OUTPUTS

SCAS131 − APRIL 1990 − REVISED APRIL 1993

Copyright

1

POST OFFICE BOX 655303

POST OFFICE BOX 1443

Synchronization Applications

Provide Greater System Reliability

PCB Layout

Minimize High-Speed Switching Noise

CMOS) 1-

mm Process

at 125

°C

Outline Packages and Standard Plastic

300-mil DIPs

description

The 74ACT11478 is an 8-bit dual-rank synchronizer circuit designed specifically for data synchronization

applications where the normal setup and hold time specifications are frequently violated.

Synchronization of two digital signals operating at different frequencies is a common system problem. This

problem is typically solved by synchronizing one of the signals to the local clock through a flip-flop. This solution,

however, causes the setup and hold time specifications associated with the flip-flop to be violated. When the

setup or hold time specification is violated, the output response is uncertain.

until the flip-flop recovers into one of its two stable states. With conventional flip-flops, this recovery time can

be longer than the specified maximum propagation delay.

The problem of metastability is typically solved by adding an additional layer of synchronization. This type of

dual ranking is employed in the 74ACT11478. The probability of the second stage entering the metastable state

is exponentially reduced by this dual-rank architecture. The 74ACT11478 provides a one-chip solution for

system designers in asynchronous applications.

The 74ACT11478 is characterized for operation from − 40

°C to 85°C.

FUNCTION TABLE

(each flip-flop)

INPUTS

OUTPUT

OE

CLOCK†

D

Q

H

X

X

Z

L

↑

LL

L

↑

HH

L

H

X

QO

† Data presented at the D input requires two

clock cycles to appear at the Q output.

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

1Q

2Q

3Q

4Q

GND

GND

GND

GND

5Q

6Q

7Q

8Q

OE

1D

2D

3D

4D

5D

6D

7D

8D

CLK

DW OR NT PACKAGE

(TOP VIEW)

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.