3-152

TELCOM SEMICONDUCTOR, INC.

ELECTRICAL CHARACTERISTICS (Cont.)

Symbol

Parameter

Test Conditions

Min

Typ

Max

Units

Buzzer Frequency

—

5

—

kHz

Counter Timebase Period

—

1

—

Second

Low Battery Flag Voltage

6.7

7

7.3

V

Input Low Voltage

—

—

DGND + 1.5

V

Input High Voltage

—

—

V

Output Low Voltage,

—

—

DGND + 0.4

V

UR, OR Outputs

Output High Voltage,

—

—

V

UR, OR Outputs

Control Pin

—5

—

µA

Pull-Down Current

PIN DESCRIPTION

Pin No.

Pin No.

(40-Pin

(44-Pin Flat

Package)

Package)

Symbol

Description

1

40

L-E4

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

significant digit (MSD).

2

41

AGD4

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

3

42

BC4P3

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

4

43

HFE3

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

5

44

AGD3

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

6

1

BC3P2

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

7

2

OFE2

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

8

3

AGD2

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

9

4

BC2P1

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

10

5

PKFE1

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

11

6

AGD1

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

12

7

BC1BT

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

13

8

BP3

LCD backplane #3.

14

9

BP2

LCD backplane #2.

15

10

BP1

LCD backplane #1.

—11

compensate for temperature variation of LCD crystal threshold voltage.

16

12

DGND

17

13

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.

18

14

LOGIC

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 connected to DGND, the TC820 is in the voltage/frequency

measurement mode. This pin has a 5

µA internal pull-down to DGND.

19

15

RANGE/

FREQ

will be 200 counts instead of 2000 counts and the LCD will display the analog input

divided by 10. (See text for limitation with TC820.) In frequency mode, this pin is the

frequency input. A digital signal applied to this pin will be measured with a 1-second

time base. There is an internal 5

µA pull-down to DGND.

3-3/4 A/D CONVERTER WITH

FREQUENCY COUNTER

AND LOGIC PROBE

TC820