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TC7126
TC7126A
3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS
FEATURES
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Low Temperature Drift Internal Reference
TC7126 ....................................... 80 ppm/
°
C Typ
TC7126A ..................................... 35 ppm/
°
C Typ
Guaranteed Zero Reading With Zero Input
Low Noise .................................................... 15
µ
V
P-P
High Resolution .............................................. 0.05%
Low Input Leakage Current ...................... 1 pA Typ
10 pA Max
Precision Null Detectors With True Polarity at
Zero
High-Impedance Differential Input
Convenient 9V Battery Operation With
Low Power Dissipation ........................ 500
µ
W Typ
900
µ
W Max
2
3
4
5
6
7
GENERAL DESCRIPTION
The TC7126A is a 3-1/2 digit CMOS analog-to-digital
converter (ADC) containing all the active components nec-
essary to construct a 0.05% resolution measurement sys-
tem. 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. Roll-over error (the difference in readings for equal
magnitude but opposite polarity input signals) is below
±1
count. High-impedance differential inputs offer 1 pA leak-
age current and a 10
12
Ω
input impedance. The 15
µV
P-P
noise performance guarantees a "rock solid" reading, and
the auto-zero cycle guarantees 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.
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TYPICAL APPLICATIONS
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Thermometry
Bridge Readouts: Strain Gauges, Load Cells, Null
Detectors
Digital Meters and Panel Meters
— Voltage/Current/Ohms/Power, pH
Digital Scales, Process Monitors
TYPICAL OPERATING CIRCUIT
ORDERING INFORMATION
PART CODE
TC7126X X XXX
A or blank*
LCD
0.1 µF
34
C+
31
33
–
C
REF
2–19 SEGMENT
22–25 DRIVE
POL
BP
V+
20
21
1
240 kΩ
36
10 kΩ
35
1 CONVERSION/SEC
+
9V
MINUS SIGN
BACKPLANE
R (reversed pins) or blank (CPL pkg only)
* "A" parts have an improved reference TC
Package Code
(see below):
Package
Code
CKW
CLW
CPL
IPL
1 MΩ
+
ANALOG
INPUT
–
0.01 µF
REF
+
V
IN
–
30 V
IN
32 ANALOG
COMMON
28
V
BUFF
Package
44-Pin PQFP
44-Pin PLCC
40-Pin PDIP
40-Pin PDIP (non-A only)
Temperature
Range
0°C to +70°C
0°C to +70°C
0°C to +70°C
– 25°C to +85°C
180 kΩ
0.33
µF
29
27
TC7126
TC7126A
+
V
REF
V–
C
AZ
V
INT
39
0.15 µF
V
OSC
2
OSC
3
OSC
1
REF
–
26
38 COSC 40
ROSC 50 pF
560 kΩ
TO ANALOG COMMON
(PIN 32)
NOTE:
Pin numbers refer to 40-pin DIP.
AVAILABLE PACKAGES
40-Pin Plastic DIP
44-Pin Plastic Quad Flat 44-Pin Plastic Chip
Package Formed Leads
Carrier PLCC
TC7126/A-8 11/6/96
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TELCOM SEMICONDUCTOR, INC.
3-217
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
