3-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTERS
TC7126
TC7126
TC7126A
TC7126A
3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS
FEATURES
GENERAL DESCRIPTION
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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 measurement 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. 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 leakage current and a 1012Ω 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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Low Temperature Drift Internal Reference
TC7126 ...................................... 80 ppm/°C Typ.
TC7126A .................................... 35 ppm/°C Typ.
Guaranteed Zero Reading With Zero Input
Low Noise ..................................................... 15µVP-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 ........................ 500µW Typ.
900µW Max
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
ORDERING INFORMATION
PART CODE
TC7126X X XXX
TYPICAL OPERATING CIRCUIT
A or blank*
0.1 µF
1 MΩ
+
ANALOG
INPUT
–
0.01 µF
33
C–
34
C+
31
2–19 SEGMENT
22–25 DRIVE
–
30 V IN
POL
BP
32 ANALOG
COMMON
28
180 kΩ
0.15 µF
0.33
µF
29
27
R (reversed pins) or blank (CPL pkg only)
LCD
REF
REF
+
V IN
VBUFF
V+
21
CAZ
Package Code (see below):
MINUS SIGN
BACKPLANE
1
240 kΩ
TC7126
TC7126A
+
VREF
* "A" parts have an improved reference TC
20
Package
Code
9V
36
10 kΩ
–
V REF 35
– 26
V
OSC2 OSC3 OSC1
39
38 COSC 40
VINT
ROSC 50 pF
560 kΩ
1 CONVERSION/SEC
TO ANALOG COMMON
(PIN 32)
Package
Temperature
Range
CKW
CLW
CPL
IPL
+
44-Pin PQFP
44-Pin PLCC
40-Pin PDIP
40-Pin PDIP (non-A only)
0°C to +70°C
0°C to +70°C
0°C to +70°C
– 25°C to +85°C
AVAILABLE PACKAGES
NOTE: Pin numbers refer to 40-pin DIP.
40-Pin Plastic DIP
TC7126/A-8 11/6/96
TelCom Semiconductor reserves the right to make changes in the circuitry and specifications of its devices.
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44-Pin Plastic Quad Flat 44-Pin Plastic Chip
Package Formed Leads
Carrier PLCC
