© 2002 Microchip Technology Inc.

DS21476B-page 7

TC820

25

21

PKHOLD

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

Under range output. This output will be HIGH when the digital reading is 380

counts or less.

—

23

OR

Over range 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 over ranged.

26

24

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

27

25

COM

28

26

Positive connection for reference capacitor.

29

27

Negative connection for reference capacitor.

30

28

High differential reference input connection.

31

29

Low differential reference input connection.

32

30

Low analog input signal connection.

33

31

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

Bi-directional pin. Pulses low (i.e., from V

37

36

OSC1

Crystal oscillator (input) connection.

38

37

OSC2

Crystal oscillator (output) connection.

39

38

OSC3

RC oscillator connection.

40

39

LCD segment drive for "a," "g," and "d" segments of MSD.

TABLE 2-1:

PIN FUNCTION TABLE (CONTINUED)

Pin Number

(40-PDIP)

Pin Number

(44-PQFP)

Symbol

Description