TC820CPL datasheet(5/22 Pages) TELCOM

5 / 22 page

3-153

TELCOM SEMICONDUCTOR, INC.

PIN DESCRIPTION

Pin No.

(40-Pin

(44-Pin Flat

Package)

Symbol

Description

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 5

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

DP1

DP0

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 5

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

µA

pull-down to DGND.

FREQ/

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.

PKHOLD

Peak hold input. When connected to VDD, the converter will only update the display

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.

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

or less.

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.

VSS

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

COM

Analog circuit ground reference point. Nominally 3.3V below VDD.

REF

Positive connection for reference capacitor.

–

REF

Negative connection for reference capacitor.

REF

High differential reference input connection.

–

REF

Low differential reference input connection.

–

Low analog input signal connection.

High analog input signal connection.

VBUFF

Buffer output. Connect to integration resistor.

CAZ

Auto-zero capacitor connection.

VINT

Integrator output. Connect to integration capacitor.

EOC/

Bidirectional pin. Pulses low (i.e., from VDD to DGND) at the end of each

HOLD

conversion. If connected to VDD, conversions will continue, but the display is not

updated.

OSC1

Crystal oscillator (input) connection.

OSC2

Crystal oscillator (output) connection.

OSC3

RC oscillator connection.

VDD

Positive power supply connection, typically 9V.

TC820

3-3/4 A/D CONVERTER WITH

FREQUENCY COUNTER

AND LOGIC PROBE

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