TC7126/A
3-1/2 Digit Analog-to-Digital Converters
Features:
• Internal Reference with Low Temperature Drift:
- TC7126: 80ppm/°C, Typical
- TC7126A: 35ppm/°C, Typical
• Zero Reading with Zero Input
• Low Noise: 15V
P-P
• High Resolution: 0.05%
• Low Input Leakage Current: 1pA Typ., 10pA Max.
• Precision Null Detectors with True Polarity at Zero
• High-Impedance Differential Input
• Convenient 9V Battery Operation with Low-Power
Dissipation: 500W Typ., 900W Max.
General Description:
The TC7126A is a 3-1/2 digit CMOS Analog-to-Digital
Converter (ADC) containing all the active components
necessary to construct a 0.05% resolution measure-
ment system. Seven-segment decoders, digit and
polarity drivers, voltage reference, and clock circuit are
integrated on-chip. The TC7126A directly drives a
Liquid Crystal Display (LCD), and includes a backplane
driver.
A low-cost, high resolution indicating meter requires
only a display, four resistors, and four capacitors. The
TC7126A’s extremely low-power drain and 9V battery
operation make it ideal for portable applications.
The TC7126A reduces linearity error to less than 1
count. Rollover error (the difference in readings for
equal magnitude, but opposite polarity input signals) is
below ±1 count. High-impedance differential inputs
offer 1pA leakage current and a 10
12
input imped-
ance. The 15V
P-P
noise performance ensures a “rock
solid” reading, and the auto-zero cycle ensures a zero
display reading with a 0V input.
The TC7126A features a precision, low drift internal
voltage reference and is functionally identical to the
TC7126. A low drift external reference is not normally
required with the TC7126A.
Applications:
• Thermometry
• Bridge Readouts: Strain Gauges, Load Cells,
Null Detectors
• Digital Meters and Panel Meters:
- Voltage/Current/Ohms/Power, pH
• Digital Scales, Process Monitors
Device Selection Table
Package
Code
CPL
IPL
CKW
CLW
Package
40-Pin PDIP
40-Pin PDIP (TC7126 Only)
44-Pin PQFP
44-Pin PLCC
Temperature
Range
0C to +70C
-25C to +85C
0C to +70C
0C to +70C
2002-2012 Microchip Technology Inc.
DS21458D-page 1
TC7126/A
Package Type
44-Pin PLCC
V
REF
+
V
REF
+
C
REF
+
V
REF
-
OSC1
OSC2
OSC3
44-Pin PQFP
ANALOG
COMMON
V
IN
+
C
REF
-
V
BUFF
TEST
V
IN
-
V
INT
C
AZ
NC
V+
C
1
D
1
A
1
B
1
6
F
1
7
G
1
8
E
1
9
D
2
10
C
2
11
NC 12
B
2
13
A
2
14
F
2
15
E
2
16
D
3
17
5
4
3
2
1
44 43 42 41 40
39 V
REF
-
38 C
REF
+
37 C
REF
-
36 ANALOG
COMMON
35 V
IN
+
34 NC
33 V
IN
-
32 C
AZ
31 V
BUFF
30 V
INT
29 V-
NC 1
NC 2
TEST 3
OSC3 4
NC 5
OSC2 6
OSC1 7
V+ 8
D
1
9
C
1
10
B
1
11
44 43 42 41 40 39 38 37 36 35 34
33 NC
32 G
2
31 C
3
30 A
3
V-
29 G
3
28 BP
27 POL
26 AB
4
25 E
3
24 F
3
23 B
3
TC7126CLW
TC7126ACLW
TC7126CKW
TC7126ACKW
18 19 20 21 22 23 24 25 26 27 28
12 13 14 15 16 17 18 19 20 21 22
AB
4
A
1
F
1
G
1
POL
BP
E
1
D
2
G
3
C
3
NC
G
2
C
2
40-Pin PDIP (Normal)
V+
D
1
C
1
B
1
1's
A
1
F
1
G
1
E
1
D
2
1
2
3
4
5
6
7
8
9
44-Pin PDIP (Reverse)
OSC1
OSC2
OSC3
TEST
1
2
3
4
Normal Pin
Configuration
40 OSC1
39
OSC2
Reverse Pin
Configuration
40 V+
39 D
1
38 C
1
37 B
1
36 A
1
35
F
1
1's
38 OSC3
37 TEST
36 V
REF
+
35 V
REF
-
REF
TC7126CPL
33 C
REF
-
TC7126ACPL
TC7126IPL
32 ANALOG
COMMON
TC7126AIPL
V
REF
+ 5
V
REF
-
C
REF
+
6
7
34 C
+
C
2
10
10's
B
2
11
A
2
12
31 V
IN
+
30 V
IN
-
29 C
AZ
TC7126RCPL
C
REF
- 8
TC7126ARCPL
33 E
1
ANALOG 9
TC7126RIPL
32 D
2
COMMON
TC7126ARIPL
V +
IN
34 G
1
10
31 C
2
30 B
2
29 A
2
28
F
2
10's
V
IN
- 11
C
AZ
12
F
2
13
E
2
14
28 V
BUFF
27 V
INT
26 V-
25 G
2
24 C
3
23 A
3
22 G
3
21 BP
(Backplane)
100's
100's
V
BUFF
13
V
INT
14
V-
15
27 E
2
26 D
3
25 B
3
24
F
3
100's
D
3
15
100's
B
3
16
G
2
16
C
3
A
3
17
18
F
3
17
E
3
18
19
23 E
3
22 AB
4
1000's
1000's
AB
4
G
3
19
BP 20
(Backplane)
POL 20
(Minus Sign)
21 POL
(Minus Sign)
NC = No Internal Connection
DS21458D-page 2
2002-2012 Microchip Technology Inc.
D
3
B
3
A
3
B
2
A
2
F
2
E
3
E
2
F
3
TC7126/A
Typical Application
0.1μF
34
1MΩ
+
Analog
Input
–
0.01μF
30 V
IN
-
32 ANALOG
COMMON
28
180kΩ
0.33
μF
29
V
BUFF
V
REF
+ 36
C
AZ
V
REF
-
V-
OSC3 OSC1
38 C
OSC
40
R
OSC
50pF
560kΩ
To Analog Common (Pin 32)
35
26
1 Conversion/Sec
POL
BP
V+
C
REF
+
31
V
IN
+
33
C
REF
-
2–19
22–25
Segment
Drive
20
21
1
240kΩ
+
9V
TC7126
TC7126A
LCD
Minus Sign
Backplane
10kΩ
0.15μF
27 V
INT
OSC2
39
Note:
Pin numbers refer to 40-pin DIP.
2002-2012 Microchip Technology Inc.
DS21458D-page 3
DS21458D-page 4
Typical Segment Output
V+
0.5mA
Segment
Output
LCD
2mA
TC7126/A
Functional Block Diagram
TC7126A
C
REF
V
REF
-
C
REF
- V
BUFF
V+
28
1
Integrator
–
–
+
–
ZI
DE
(+)
–
DE (–)
V+ – 2.8V
Clock
AZ & DE (±)
26
V-
40
OSC1
39
OSC2
R
OSC
38
OSC3
C
OSC
+
Low
Temp Co
V
REF
Comparator
Thousands
BP
21
R
INT
V
INT
29
27
7-Segment
Decode
To Digital
Section
Data Latch
7-Segment
Decode
7-Segment
Decode
¸ 200
C
AZ
C
INT
LCD Segment Drivers
C
REF
+
35
33
V
REF
+
34
36
ZI & AZ
+
AZ
+
10
μA
ZI &
AZ
V
IN
+
31
Hundreds
Tens
Units
INT
DE
(–)
To Switch Drivers From
Comparator Output
F
OSC
4
Internal Digital Ground
V
TH
= 1V
Control Logic
1
6.2V
Analog
Common
32
DE (+)
V+
V
IN
-
TEST
500Ω
26
V-
2002-2012 Microchip Technology Inc.
INT
TC7126/A
1.0
ELECTRICAL
CHARACTERISTICS
*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.
Absolute Maximum Ratings*
Supply Voltage (V+ to V-)....................................... 15V
Analog Input Voltage (either Input)
(Note 1)
... V+ to V-
Reference Input Voltage (either Input) ............ V+ to V-
Clock Input ................................................... Test to V+
Package Power Dissipation (T
A
70°C)
(Note 2):
44-Pin PQFP............................................... 1.00W
40-Pin PLCC ............................................... 1.23W
44-Pin PDIP ................................................ 1.23W
Operating Temperature Range:
C (Commercial) Devices .................. 0°C to +70°C
I (Industrial) Devices .................... -25°C to +85°C
Storage Temperature Range.............. -65°C to +150°C
TABLE 1-1:
Symbol
Input
Z
IR
Z
RD
TC7126/A ELECTRICAL SPECIFICATIONS
Parameter
Min
Typ
Max
Unit
Test Conditions
Electrical Characteristics:
V
S
= +9V, f
CLK
– 16kHz, and T
A
= +25°C, unless otherwise noted.
Zero Input Reading
Zero Reading Drift
Ratiometric Reading
-000.0
—
999
-1
±000.0
0.2
999/1000
±0.2
+000.0
1
1000
1
Digital
Reading
V/°C
Digital
Reading
Count
V
IN
= 0V
Full Scale = 200mV
V
IN
= 0V, 0°C
T
A
+70°C
V
IN
= V
REF
, V
REF
= 100mV
Full Scale = 200mV or 2V
Max Deviation From Best Fit
Straight Line
V
IN
- = V
IN
+
200mV
V
IN
= 0V, Full Scale = 200mV
V
IN
= 0V
V
CM
= ±1V, V
IN
= 0V
Full Scale = 200mV
V
IN
= 199mV, 0°C
T
A
+70°C
Ext. Ref. Temp Coeff. = 0ppm/°C
NL
Linearity Error
Rollover Error
e
N
I
L
CMRR
Noise
Input Leakage Current
Common Mode Rejection Ratio
Scale Factor Temperature
Coefficient
Analog Common
V
CTC
Analog Common Temperature
Coefficient
-1
—
—
—
—
±0.2
15
1
50
1
1
—
10
—
5
Count
V
P-P
pA
V/V
ppm/°C
—
—
—
—
—
—
—
80
35
35
—
—
—
75
100
—
—
ppm/°C
ppm/°C
ppm/°C
250k Between Common and V+
0°C
T
A
+70°C (“C” Devices)
TC7126
TC7126A
-25°C
T
A
+85°C (“I” Device)
(TC7126A)
Note 1:
2:
3:
4:
Input voltages may exceed the supply voltages, provided the input current is limited to ±100A.
Dissipation rating assumes device is mounted with all leads soldered to printed circuit board.
Refer to “Differential Input” discussion.
Backplane drive is in phase with segment drive for “OFF” segment, 180° out of phase for “ON” segment. Frequency is
20 times conversion rate. Average DC component is less than 50mV.
5:
See “Typical Application”.
6:
During Auto-Zero phase, current is 10-20A higher. A 48kHz ocillator increases current by 8A (Typical). Common
current is not included.
2002-2012 Microchip Technology Inc.
DS21458D-page 5
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