MC74HC4040A

http://onsemi.com

7

Clock

Reset

Q1

1

2

4

8

16

32

64

128

256

512

1024

2048

4096

Q2

Q3

Q4

Q5

Q6

Q7

Q8

Q10

Q11

Figure 8. Timing Diagram

Q9

Q12

APPLICATIONS INFORMATION

Time−Base Generator

A 60Hz sinewave obtained through a 100 K resistor

connected to a 120 Vac power line through a step down

transformer is applied to the input of the MC54/74HC14A,

Schmitt-trigger inverter. The HC14A squares−up the input

waveform and feeds the HC4040A. Selecting outputs Q5,

Q10, Q11, and Q12 causes a reset every 3600 clocks. The

HC20 decodes the counter outputs, produces a single

(narrow) output pulse, and resets the binary counter. The

resulting output frequency is 1.0 pulse/minute.

HC4040A

Figure 9. Time−Base Generator

Clock

Q5

Q10

Q11

Q12

13

12

10

9

1

2

4

5

8

1/2

HC20

1/2

HC20

6

1.0 Pulse/Minute

Output

≥20pF

1.0M

120Vac

60Hz

NOTE:

Ground MUST be isolated

by a transformer or

opto−isolator for safety

reasons.