5

Digital Timer Application

A positive pulse on MASTER RESET resets the counters

and latch. The output goes high and remains high until the

number of pulses, selected by A and B, are counted. This

circuit is retriggerable and is as accurate as the input fre-

quency. If additional accuracy is desired, an external clock

can be used on pin 3. A setup time equal to the width of the

one-shot output is required immediately following initial

power up, during which time the output will be high.

1

2

3

4

5

6

7

14

13

12

11

10

9

8

AR

MR

INPUT

B

A

t

OUTPUT

FIGURE 3. DIGITAL TIMER APPLICATION CIRCUIT

82

80

70

60

50

40

30

20

10

0

0

10

20

304050

60

70

80

88

79 - 87

(2.007 - 2.210)

4 - 10

(0.102 - 0.254)

85 - 93

(2.159 - 2.362)

NOTE: Dimensions in parentheses are in millimeters and are de-

rived from the basic inch dimensions as indicated. Grid graduations

FIGURE 4. DIMENSIONS AND PAD LAYOUT FOR CD4541B

CD4541B