
4
3-3/4 A/D Converter with Frequency
Counter and Logic Probe
TC820
TC820-10 10/17/96
2001 Microchip Technology Inc.
DS21476A
ELECTRICAL CHARACTERISTICS (Cont.)
Symbol
Parameter
Test Conditions
Min
Typ
Max
Units
Buzzer Frequency
fOSC = 40kHz
—
5
—
kHz
Counter Timebase Period
fOSC = 40kHz
—
1
—
Second
Low Battery Flag Voltage
VDD to VSS
6.7
7
7.3
V
VIL
Input Low Voltage
—
DGND + 1.5
V
VIH
Input High Voltage
VDD – 1.5
—
V
VOL
Output Low Voltage,
IL = 50A
—
DGND + 0.4
V
UR, OR Outputs
VOL
Output High Voltage,
IL = 50AVDD – 1.5
—
V
UR, OR Outputs
Control Pin
VIN = VDD
—5
—
A
Pull-Down Current
PIN DESCRIPTION
Pin No.
(40-Pin Plastic (44-Pin Plastic
DIP Pkg.)
Flat Pkg.)
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
VDISP
Sets peak LCD drive signal: VPEAK = (VDD ) –VDISP. VDISP may also be used to
compensate for temperature variation of LCD crystal threshold voltage.
16
12
DGND
Internal logic digital ground, the logic "0" level. Nominally 4.7V below VDD.
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
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 connected to DGND, the TC820 is in the voltage/frequency
measurement mode. This pin has a 5
A internal pulldown to DGND.
19
15
RANGE/
Dual-purpose input. In range mode, when connected to VDD, the integration time
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
A pulldown to DGND.