TC820 datasheet(6/28 Pages) MICROCHIP

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TC820

DS21476B-page 6

2.0

PIN DESCRIPTIONS

Thedescriptionsof the pins arelistedinTable2-1.

TABLE 2-1:

PIN FUNCTION TABLE

Pin Number

(40-PDIP)

Pin Number

(44-PQFP)

Symbol

Description

L-E4

LCD segment driver for L ("logic LOW"), polarity, and "e" segment of most significant

digit (MSD).

AGD4

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

BC4P3

LCD segment drive for "b" and "c" segments of MSD and decimal point 3.

HFE3

LCD segment drive for H ("logic HIGH"), and "f" and "e" segments of third LSD.

AGD3

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

BC3P2

LCD segment drive for "b" and "c" segments of third LSD and decimal point 2.

OFE2

LCD segment drive for "over range," and "f" and "e" segments of second LSD.

AGD2

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

BC2P1

LCD segment drive for "b " and "c" segments of second LSD and decimal point 1.

PKFE1

LCD segment drive for "hold peak reading," and "f" and "e" segments of LSD.

AGD1

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

BC1BT

LCD segment drive for "b" and "c" segments of LSD and "low battery."

BP3

LCD backplane #3.

BP2

LCD backplane #2.

BP1

LCD backplane #1.

—11

VDISP

Sets peak LCD drive signal: VPEAK =(VDD)– VDISP.VDISP mayalso beusedto

compensate for temperature variation of LCD crystal threshold voltage.

DGND

Internal logic digital ground, the logic "0" level. Nominally 4.7V below VDD.

ANNUNC

Square-wave output at the backplane frequency, synchronized to BP1. ANNUNC can be

used to control display annunciators. Connecting an LCD segment to ANNUNC turns it

on; connecting it to its backplane turns it off.

LOGIC

Logic mode control input. When connected to VDD, the converter is in Logic mode. The

LCD displays "OL" and the decimal point inputs control the HIGH and LOW annunciators.

When the "low" annunciator is on, the buzzer will also be on. When unconnected or con-

nected to DGND, the TC820 is in the Voltage/Frequency Measurement mode. This pin

has a 5

µA internal pull-down to DGND.

RANGE/

FREQ

Dual purpose input. In Range mode, when connected to VDD, the integration time

will be 200 counts instead of 2000 counts

DP0/LO

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

connecting this pin to VDD will turn on the "low" LCD segment. There is an internal 5µA

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

DP1

DPQ

Decimal Point Selected

None

DP1

DP2

DP3

DP1/HI

Dual purpose input. Decimal point select input for voltage measurements. In Logic mode,

connecting this pin to VDD will turn on the "high" LCD segment. There is an internal 5µA

pull-down to DGND in Volts mode only.

BUZOUT

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

BUZIN

Buzzer control input. Connecting BUZIN to VDD turns the buzzer on. BUZIN is logically

OR’ed (internally) with the "logic level low" input. There is an internal 5

µApull-down to

DGND.

FREQ/

VOLTS

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

VOLTS to DGND, the A/D converter function is active. When connected to VDD,the

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

µA pull-down to DGND.

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