HIT HD74HC78 Datasheet

HD74HC78

Dual J-K Flip-Flops (with Preset, Common Clear and

Common Clock)

Description

This flip-flop is edge sensitive to the clock input and change state on the negative transition of the clock
pulse. Each flip-flop has independent J, K, and preset inputs and Q and Q outputs. Two flip-flops are
controlled by a common clear and a common clock. Preset and clear are independent of the clock and
accomplished by a low logic level on the corresponding input.

Features

• High Speed Operation: tpd (Clock to Q) = 20 ns typ (CL = 50 pF)

• High Output Current: Fanout of 10 LSTTL Loads

• Wide Operating Voltage: VCC = 2 to 6 V

• Low Input Current: 1 µA max

• Low Quiescent Supply Current: ICC (static) = 2 µA max (Ta = 25°C)

HD74HC78

(

)

Function Table

Inputs Outputs
Preset Clear Clock J K Q Q

LHXXXHL
HLXXXL H
LLXXXH*
HH L L No change

HH LHLH
HH HLHL
HH H H Toggle
H H L X X No change

H H H X X No change
HH X X No change
Note: 1. Q and Q will remain HIGH as long as Preset and Clear are Low, but Q and Q are unpredictable,

if Preset and Clear go HIGH simultaneously.

1

H*

1

Pin Arrangement

CK

1PR

1J

V

CC

CLR

2PR

2K

14

13

12

11

10

1K

1Q

1Q

GND

2J

9

2Q

8

2Q

1

2

3

4

5

6

7

K

CLR PR

Q Q

K

CLR PR

Q Q

Top view

CK

CK

J

J

2

Block Diagram (1//2)

HD74HC78

To Other FF

PR

CLR

#
CK

Q

CK

J

K

CK

To Other FF

CK

#

CK

CK

CKCK

CK

CK

#

CK

#

CK

#

CK

Q

3