HIGH TECH

CHIPS, INC.

01/04/00

2

With this application we can generate thirty-two different output frequencies. See output frequency

selection table for dip switch settings. Setting “Frequency Selection” dip switch sets frequency.

HTC555 reads input switch value constantly and output frequency is set per new value if D[0:4] inputs

are changed. Time that takes to change output frequency to new value is relative to period of

previous frequency setting. For example if HTC555 was generating 10000Hz clock and we changed it

to 25000Hz clock, then output frequency will change in 1/10000Hz or 100uS. In order to avoid output

glitches, HTC555 changes its output frequency after finishing current output period. R1-R5 value

could be in a range of 1K to 10K in this application. Please note that if only one frequency is needed

then we can connect D [0:4] pins directly to ground or VDD. C1 is used, as de-coupling capacitor and

could be omitted.

3.0 Pin out description.

Abbreviations used: O - output, I - input, P - power.

Pin number

Name

I / O

Description

Notes

1

VDD

P

Power

+2.5V to + 5.5V.

2

CLKOUT

O

Clock Output

Output frequency.

3

D4

I

Frequency selector input.

Tie to GND or VDD.

4

D3

I

Frequency selector input.

Tie to GND or VDD.

5

D2

I

Frequency selector input.

Tie to GND or VDD.

6

D1

I

Frequency selector input.

Tie to GND or VDD.

7

D0

I

Frequency selector input.

Tie to GND or VDD.

8

GND

P

Ground

Connect to ground.

Output Frequency Selection.

Abbreviations used: 0 – connection to GND, 1 – connection to VDD.

D4

D3

D2

D1

D0

CLK ( output frequency)

00

0

0

0

1Hz

0

0

0

0

1

10 Hz

0

0

0

1

0

20 Hz

0

0

0

1

1

30 Hz

0

0

1

0

0

40 Hz

0

0

1

0

1

50 Hz

0

0

1

1

0

60 Hz

0

0

1

1

1

70 Hz

0

1

0

0

0

80 Hz

0

1

0

0

1

90 Hz

0

1

0

1

0

100 Hz

0

1

0

1

1

200 Hz

0

1

1

0

0

300 Hz

0

1

1

0

1

400 Hz

0

1

1

1

0

500 Hz