3-153

TELCOM SEMICONDUCTOR, INC.

7

6

5

4

3

1

2

8

PIN DESCRIPTION

Pin No.

Pin No.

(40-Pin

(44-Pin Flat

Package)

Package)

Symbol

Description

20

16

DP0/LO

Dual-purpose input. Decimal point select input for voltage measurements. In logic

internal 5

µA pull-down to DGND in volts mode only. Decimal point logic:

DP1

DP0

Decimal Point Selected

0

0

None

0

1

DP1

1

0

DP2

1

1

DP3

21

17

DP1/HI

Dual-purpose input. Decimal point select input for voltage measurements. In logic

internal 5

µA pull-down to DGND in volts mode only.

22

18

BUZOUT

Buzzer output. Audio frequency, 5kHz, output which drives a piezoelectric buzzer.

23

19

BUZIN

logically ORed (internally) with the "logic level low" input. There is an internal 5

µA

pull-down to DGND.

24

20

FREQ/

Voltage or frequency measurement select input. When unconnected, or connected

VOLTS

frequency counter function is active. This pin has an internal 5

µA pull-down

to DGND.

25

21

PKHOLD

if a new conversion value is greater than the preceding value. Thus, the peak

reading will be stored and held indefinitely. When unconnected, or connected to

DGND, the converter will operate normally. This pin has an internal 5

µA pull-down

to DGND.

22

UR

Underrange output. This output will be HIGH when the digital reading is 380 counts

or less.

23

OR

Overrange output. This output will be HIGH when the analog signal input is greater

than full scale. The LCD will display "OL" when the input is overranged.

26

24

Negative supply connection. Connect to negative terminal of 9V battery.

27

25

COM

28

26

C

+

REF

Positive connection for reference capacitor.

29

27

C

–

REF

Negative connection for reference capacitor.

30

28

V

+

REF

High differential reference input connection.

31

29

V

–

REF

Low differential reference input connection.

32

30

V

–

IN

Low analog input signal connection.

33

31

V

+

IN

High analog input signal connection.

34

32

Buffer output. Connect to integration resistor.

35

33

Auto-zero capacitor connection.

36

34

Integrator output. Connect to integration capacitor.

35

EOC/

HOLD

updated.

37

36

OSC1

Crystal oscillator (input) connection.

38

37

OSC2

Crystal oscillator (output) connection.

39

38

OSC3

RC oscillator connection.

40

39

Positive power supply connection, typically 9V.

TC820

3-3/4 A/D CONVERTER WITH

FREQUENCY COUNTER

AND LOGIC PROBE