© 2005 Microchip Technology Inc. DS21461C-page 1
TC7136/TC7136A
Features
• Fast Over Range Recovery, Ensured First Reading
Accuracy
• Low Temperature Drift Internal Reference
- TC7136: 70ppm/°C (Typ.)
- TC7136A: 35ppm/°C (Typ.)
• Zero Reading with Zero Input
• Low Noise: 15μV
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: 500μW (Typ.)/900μW (Max.)
Applications
• Thermometry
• Bridge Readouts: Strain Gauges, Load Cells,
Null Detectors
• Digital Meters: Voltage/Current/Ohms/Power, pH
• Digital Scales, Process Monitors
• Portable Instrumentation
Device Selection Table
General Description
The TC7136 and TC7136A are low power, 3-1/2 digit
with liquid crystal display (LCD) drivers and analog-to-
digital converters. These devices incorporate an "inte-
grator output zero" phase, which enables over range
recovery. The performance of existing TC7126,
TC7126A and ICL7126 based systems may be
upgraded with minor changes to external, passive
components.
The TC7136A has an improved internal zener refer-
ence voltage circuit which maintains the analog com-
mon temperature drift to 35ppm/°C (typical) and
75ppm/°C (maximum). This represents an improve-
ment of two to four times over similar 3-1/2 digit con-
verters. The costly, space consuming external
reference source may be removed.
The TC7136 and TC7136A limit linearity error to less
than 1 count on 200mV or 2V full scale ranges. The roll-
over error (the difference in readings for equal magni-
tude, but opposite polarity input signals) is below ±1
count. High-impedance differential inputs offer 1pA
leakage currents and a 10
12
Ω input impedance. The
differential reference input allows ratiometric measure-
ments for ohms or bridge transducer measurements.
The 15μV
P-P
noise performance ensures a "rock solid"
reading. The auto-zero cycle enables a zero display
readout for a 0V input.
Part Number Package
Temperature
Range
TC7136 CPI 40-Pin PDIP 0°C to +70°C
TC7136 CKW 44-Pin PQFP 0°C to +70°C
TC7136 CLW 44-Pin PLCC 0°C to +70°C
TC7136A CPI 40-Pin PDIP 0°C to +70°C
TC7136A CKW 44-Pin PQFP 0°C to +70°C
TC7136A CLW 44-Pin PLCC 0°C to +70°C
Low Power 3-1/2 Digit Analog-to-Digital Converter
Obsolete Device