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2002 Microchip Technology Inc.
DS21475B-page 1
TC818A
Features
Auto-Ranging Analog-to-Digital Converter with
3-1/2 Digit Display
Annunciator Outputs Permit Customizing of LCD
Auto-Range Operation for AC and DC Voltage
and Resistance Measurements
Two User Selected AC/DC
Current Ranges: 20mA and 200mA
22 Operating Ranges: 9 DC/AC Voltage
4 AC/DC Current
9 Resistance and Low Power Ohms
Display Hold Function
3-1/2 Digit Resolution in Auto-Range
Mode: 1/2000
Extended Resolution in Manual Range
Mode: 1/3000
Internal AC-to-DC Conversion Op Amp
Triplex LCD Drive for Decimal Points, Digits,
Bar Graphs, and Annunciators
Continuity Detection and Piezoelectric
Transducer Driver
Low Drift Internal Reference: 75ppm/C
9V Battery Operation: 10mW
Low Battery Detection and LCD Annunciator
Device Selection Table
General Description
The TC818A is an integrating analog-to-digital con-
verter (ADC) with a 3-1/2 digit numeric LCD driver,
automatic ranging, and single 9V battery operation.
The numeric display provides 0.05% resolution and a
full set of annunciators that spell out the TC818A's
many operating modes.
Automatic range selection is provided for both voltage
(DC and AC) and ohms (high and low power) measure-
ments.
Expensive
and
bulky
mechanical
range
switches are not required. Five full scale ranges are
available, with automatic selection of external volt/ohm
attenuators over a 1 to 10,000 range. Two current
ranges, 20mA and 200mA, can be manually selected.
The auto-range feature can be bypassed, allowing
input attenuator selection through a single line input.
During Manual mode operation, resolution is extended
to 3000 counts full scale. Extended resolution is also
available during 2000k
and 2000V full scale auto-
range operation. The extended range operation is indi-
cated by a flashing 1 MSD and by the fully extended bar
graph.
The TC818A includes an AC-to-DC converter for AC
voltage and current measurements. Only external
diodes/resistors/capacitors are required. Other fea-
tures include a Memory mode, low battery detection,
display HOLD input, and continuity buzzer driver.
The 3-1/2 digit numeric display includes a full set of
annunciators. Decimal points are adjusted as auto-
matic or manual range changes occur, and Voltage,
Current, and Ohms Operating modes are displayed.
Additional annunciators are activated for manual, auto,
memory, HOLD, AC, low power ohms, and low battery
conditions.
The TC818A is available in a surface mounted 64-pin
flat package. Combining a numeric display driver, sin-
gle 9V battery operation, internal range switching, and
compact surface mounting, the TC818A is ideal for
advanced portable instruments.
Part Number
Package
Operating
Temperature Range
TC818ACBU
64-Pin PQFP
0
C to +70
C
Auto-Ranging Analog-to-Digital Converter
with 3-1/2 Digit Display
TC818A
DS21475B-page 2
2002 Microchip Technology Inc.
Package Type
47
52
51
50
49
64
63
62
58
57
56
55
54
53
60
59
24
25
26
27
28
29
30
18
19
20
21
22
23
32
17
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
45
44
43
42
41
40
39
38
37
36
35
34
33
48
TC818A
R
X
CFI
ADI
ADO
R
BUF
RVIBUF
ACVH
DGND
RANGE
-MEM
I
HOLD
C
REFL
RM
REFL
DEINT
COM
V
CC
AC/-/AUTO
BCP3
ANNUNC
FE2
AGD2
-MEM/BATT
BCP2
FE1
AGD1
BCP1
C
I
ACVL
I
I
C
REFH
REFHI
R3
V
I
VR4
VR5
VR2
VR3
R5
R4
R2
R1
DC(
)/
AC(LO
)
V
SS
C
AZ
LCD
Backplanes
LCD Segment Drives
16
OHM
20mA
BUZ
FE0
AGD0
BCP0
XTAL1
XTAL2
V
DISP
BP1
BP2
BP3
LO
/A
/V
k/m/
HOLD
NC
46
NC
61
NC
31
NC
64-Pin PQFP
2002 Microchip Technology Inc.
DS21475B-page 3
TC818A
Typical Application
50
TC818A
0.1F
LCD Bias
R7/100k
R6/100k
Z1
6.2V
31
39
1.6385M
0.1
F
R8/220
(PTC)
38
37
36
35
R5 (10,000)
R4 (1,000)
R3 (100)
R2 (10)
R1 (1)
RM
REFL
R
X
78
9
10
27
163.85k
R2/1638.5
R1/163.85
R3/16.385k
Ohms Range Attenuator
V
DISP
BP3
ANNUNC
LO
/A
/V
k/m/
HOLD
MEM/
BATT
FE2
FE1
BCP2
AGD1
BCP1
FE0
AGD0
BCP0
XTAL1
DEINT
5
30
6
28
57
14
15
16
18
19
20
21
22
23
24
26
25
13
12
11
-MEM
LO
+
AC
mVA
32.768kHz
(~ 33kHz)
39pF
9V
58
XTAL2
V
SS
45
DGND
V
62
59
61
RANGE
-MEM
BUZ
4
Enable
Audio
Transducer
Current
Input
20mA
200mA
R15
D3
D4
R16
I
I
Voltage
Input
R14/9.9M
44
R13*
500k
R12/1.111M
R11/101k
41
R10/10k
VR1
Voltage Range Attenuator
(1)
VR2
(10)
VR3
(100)
VR4
(1,000)
VR5
(10,000)
ADO
R9/1k
40
43
34
53
D1
29
REFHI
COM
33
C
REF
32
C
F
I
51
R20
100k
C6
0.01F
60
HOLD
C
I
47
R26/3k
R27/2k
+
C5/1F
R24/10k
R23/10k
ADI
R21/2.2M
52
+
R22/470k
C4/1F
4.7F
C2/0.22F
ACVH
56
C1/1F
ACVL
46
R
BUF
RVIBUF
49
RVIBUF
55
R
BUF
C
AZ
0.1F
150
k
220
k
SYNC
Backplane
Drivers
1000's
Segment and Decimal Point Drive
1
9
W
163.85mV
Positive
Temperature
Coefficient
Resistor
AUTO
HOLD
R19/5k
V
CC
*Not required when Resistor Network is used.
(See Applications Section for details.)
D2
AGD2
C
AZ
V
CC
42
C
INT
C
REFL
C
REFH
DC/AC or
/LO
k
BP1
BP2
BCP3
AC//
AUTO
100's
10's
1's
Display
Annunciators
COM
R18/24k
Resistance
Input
54
HOLD
200mA
20mA
200mA
OHM
3
2
63
200mA
20mA
I
V
TC818A
DS21475B-page 4
2002 Microchip Technology Inc.
1.0
ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings*
Supply Voltage ....................................................... 15V
Analog Input Voltage ..................................V
CC
to V
SS
Reference Input Voltage..............................V
CC
to V
SS
Voltage at Pin 43 ................................. Common 0.7V
Power Dissipation ............................................800mW
Operating Temperature Range................ 0C to +70C
Storage Temperature Range .............. -65C to +150C
*Stresses above those listed under "Absolute Maximum
Ratings" may cause permanent damage to the device. These
are stress ratings only and functional operation of the device
at these or any other conditions above those indicated in the
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability.
TC818A ELECTRICAL SPECIFICATIONS
Electrical Characteristics: V
A
= 9V, T
A
= +25C, unless otherwise specified.
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
Zero Input Reading
-0000
0000
+0000
Digital
Reading
200mV Range without 10M
Resistor
-0001
--
+0001
Digital
Reading
200mV Range with 10M
Resistor
-0000
0000
+0000
Digital
Reading
20mA and 200mA Range
RE
Rollover Error
--
--
1
Counts
200mV Range without 10M
Resistor
--
--
3
200mV Range with 10M
Resistor
--
--
1
20mA and 200mA Range
NL
Linearity Error
--
--
1
Count
Best Case Straight Line
I
IN
Input Leakage Current
--
--
10
pA
E
N
Input Noise
--
20
--
V
P-P
BW = 0.1 to 10Hz
AC Frequency Error
--
1
--
%
40 to 500Hz
--
5
--
%
Error 40 to 2000Hz
Open Circuit Voltage for Ohm
Measurements
--
570
660
mV
Excludes 200
Range
Open Circuit Voltage for LO Ohm
Measurements
--
285
350
mV
Excludes 200
Range
V
COM
Analog Common Voltage
2.8
3
3.3
V
(V
CC
- V
COM
)
V
CTC
Common Voltage Temperature
Coefficient
--
--
50
ppm/C
Display Multiplex Rate
--
100
--
Hz
V
IL
Low Logic Input
--
--
1
A
20mA, AC, I, LOW
, HOLD
Range, -MEM, OHMs
(Relative to DGND, Pin 58)
Logic 1 Pull-up Current
--
25
--
V
20mA, AC, I, LOW
, HOLD
Range, -MEM, OHMs
(Relative to DGND, Pin 58)
V
OL
Low Logic Output
--
DGND +0.1
--
V
ANNUNC, DEINT: I
L
= 100
A
V
OH
High Logic Output
--
V
CC
- 0.1
--
V
ANNUNC, DEINT: I
L
= 100
A
Buzzer Drive Frequency
--
4
--
kHz
Low Battery Flag Voltage
6.3
6.6
7
V
V
CC
to V
SSA
Operating Supply Current
--
0.8
1.5
mA
2002 Microchip Technology Inc.
DS21475B-page 5
TC818A
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
Pin Number
(64-Pin PQFP)
Symbol
Description
1
NC
No connection.
2
OHM
Logic Input. "0" (Digital Ground) for resistance measurement.
3
20mA
Logic Input. "0" (Digital Ground) for 20mA full scale current measurement.
4
BUZ
Buzzer. Audio frequency, 4kHz, output for continuity indication during resistance
measurement. A noncontinuous 4kHz signal is output to indicate an input over range
during voltage or current measurements.
5
XTAL1
32.768kHz Crystal Connection.
6
XTAL2
32.768kHz Crystal Connection.
7
V
DISP
Sets peak LCD drive signal: V
P
- V
DD
-V
DISP
. V
DISP
may also be used to compensate for
temperature variation of LCD crystal threshold voltage.
8
BP1
LCD Backplane #1.
9
BP2
LCD Backplane #2.
10
BP3
LCD Backplane #3.
11
LO
/A
LCD Annunciator segment drive for low ohms resistance measurement and current
measurement.
12
/V
LCD Annunciator segment drive for resistance measurement and voltage measurement.
13
k/m/HOLD
LCD Annunciator segment drive for k ("kilo-Ohms"), m ("milliamps" and "millivolts") and
HOLD mode.
14
BCP0
(One's digit)
LCD segment drive for "b," "c" segments and decimal point of least significant digit (LSD).
15
AGD0
LCD segment drive for "a," "g," "d" segments of LSD.
16
FE0
LCD segment drive for "f" and "e" segments of LSD.
17
NC
No connection.
18
BCP1
LCD segment drive for "b," "c" segments and decimal point of 2nd LSD.
19
AGD1
LCD segment drive for "a," "g," "d" segments of 2nd LSD.
20
FE1
LCD segment drive for "f" and "e" segments of 2nd LSD.
21
BCP2
LCD segment drive for "b," "c" segments and decimal point of 3rd LSD
(hundred's digit).
22
AGD2
LCD segment drive for "a," "g," "d" segments of 3rd LSD.
23
FE2
LCD segment drive for "f," "e" segments of 3rd LSD.
24
BCP3
LCD segment drive for "b," "c" segments and decimal point of MSD,
(thousand's digit).
25
AC/-/AUTO
LCD annunciator segment drive for AC measurements, polarity, and auto-range operation.
26
-MEM/BATT LCD annunciator segment drive for AC for low battery indication and memory (relative
measurement).
27
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.
28
V
CC
Positive battery supply connection.
29
COM
Analog circuit ground reference point. Nominally 3V below V
CC
.
30
DEINT
De-integrate output.
31
RM
REFL
Ratiometric (resistance measurement) reference low voltage.
32
C
REFL
Reference capacitor negative terminal C
REF
= 0.1
f.
33
C
REFH
Reference capacitor positive terminal C
REF
= 0.1
f.
34
REFHI
Reference voltage for voltage and current measurement. Nominally 163.85mV.
35
R1
Standard resistor connection for 200
full scale.
36
R2
Standard resistor connection for 2000
full scale.
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