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TC7126
TC7126A
3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS
GENERAL DESCRIPTION
FEATURES
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 1012Ω input impedance. The 15 µVP-P
noise performance guarantees a "rock solid" reading, and
the auto-zero cycle guarantees a zero display reading with
a 0V input.
■ Low Temperature Drift Internal Reference
TC7126 ....................................... 80 ppm/°C Typ
TC7126A ..................................... 35 ppm/°C Typ
■ Guaranteed Zero Reading With Zero Input
■ Low Noise.................................................... 15 µVP-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 µW Typ
900 µW Max
TYPICAL APPLICATIONS
■ Thermometry
■ Bridge Readouts: Strain Gauges, Load Cells, Null
Detectors
■ Digital Meters and Panel Meters
— Voltage/Current/Ohms/Power, pH
■ Digital Scales, Process Monitors
The TC7126A features a precision, low-drift internal
voltagereferenceandisfunctionallyidenticaltotheTC7126.
A low-drift external reference is not normally required with
the TC7126A.
TYPICAL OPERATING CIRCUIT
ORDERING INFORMATION
PART CODE
TC7126X X XXX
0.1 µF
A or blank*
33
–
34
C
R (reversed pins) or blank (CPL pkg only)
* "A" parts have an improved reference TC
Package Code (see below):
LCD
+
C
REF
REF
1 MΩ
31
SEGMENT
DRIVE
+
2–19
+
V
IN
22–25
ANALOG
INPUT
–
0.01 µF
20
–
30
32
POL
BP
V
IN
MINUS SIGN
21
1
BACKPLANE
ANALOG
COMMON
Package
Code
Temperature
+
V
Package
Range
28
V
240 kΩ
BUFF
+
TC7126
TC7126A
CKW
CLW
CPL
IPL
44-Pin PQFP
0°C to +70°C
0°C to +70°C
9V
0.33
µF
180 kΩ
36
44-Pin PLCC
+
V
29
REF
10 kΩ
C
V
AZ
40-Pin PDIP
0°C to +70°C
–
35
26
0.15 µF
V
REF
27
40-Pin PDIP (non-A only)
– 25°C to +85°C
–
V
INT
1 CONVERSION/SEC
OSC OSC OSC
2
3
1
AVAILABLE PACKAGES
C
39
38
40
OSC
TO ANALOG COMMON
(PIN 32)
50 pF
R
OSC
NOTE: Pin numbers refer to 40-pin DIP.
560 kΩ
40-Pin Plastic DIP
44-Pin Plastic Quad Flat
Package Formed Leads
44-Pin Plastic Chip
Carrier PLCC
TC7126/A-8 11/6/96
TELCOM SEMICONDUCTOR, INC.
3-217