
2002 Microchip Technology Inc.
DS21458B-page 1
TC7126/A
Features
Internal Reference with Low Temperature Drift
- TC7126: 80ppm/°C Typical
- TC7126A: 35ppm/°C Typical
Zero Reading with Zero Input
Low Noise: 15VP-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: 500
WTyp., 900WMax.
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
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 liq-
uid 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 1012
input imped-
ance. The 15
VP-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.
Package
Code
Package
Temperature
Range
CPL
40-Pin PDIP
0
°Cto +70°C
IPL
40-Pin PDIP (TC7126 Only)
-25
°Cto +85°C
CKW
44-Pin PQFP
0
°Cto +70°C
CLW
44-Pin PLCC
0
°Cto +70°C
3-1/2 Digit Analog-to-Digital Converters