ICL7106

ICL7106: 3½ Digit Analog-to-Digital Converter (ADC) with LCD Driver

Overview

The Harris ICL7106 is a precision, low-power, 3½-digit analog-to-digital converter (ADC) designed for use in digital panel meters and other measurement applications. It integrates a complete ADC, reference voltage source, clock oscillator, and LCD display driver, making it a highly versatile solution for converting analog signals into a digital readout. The ICL7106 is optimized for accuracy, offering true differential inputs and a guaranteed zero reading for 0V input across all scales. Its low power consumption and high input impedance make it ideal for battery-operated and precision measurement systems.

Features

• High Accuracy: Guaranteed zero reading for 0V input on all scales with true polarity at zero for precise null detection.
• Low Input Current: Typical input current of just 1pA, minimizing loading effects on the measured signal.
• True Differential Input and Reference: Allows for flexible measurement configurations and improved noise rejection.
• Low Noise Performance: Less than 15µV peak-to-peak noise ensures stable and accurate readings.
• Integrated Clock and Reference: On-chip oscillator and reference voltage eliminate the need for external components.
• Low Power Consumption: Typically dissipates less than 10mW, making it suitable for portable applications.
• Direct LCD Drive: Includes built-in drivers for LCD displays (ICL7106 variant).
• LED Drive Option: The ICL7107 variant supports LED displays for applications requiring higher brightness.
• Compact Packaging: Available in 40-lead DIP and 44-lead metric quad flatpack (MQFP) for space-constrained designs.

Applications

The ICL7106 is widely used in precision measurement and display systems, including:

• Digital panel meters (voltage, current, resistance)
• Portable multimeters and test equipment
• Temperature measurement systems
• Battery-powered instrumentation
• Process control and monitoring
• Medical and laboratory equipment

Electrical Characteristics

The ICL7106 operates under the following key electrical specifications:

• Supply Voltage: Typically operates from a single +5V supply.
• Input Voltage Range: Differential input range of ±200mV or ±2V, selectable via external configuration.
• Conversion Rate: Adjustable via external clock components, typically 1-3 conversions per second.
• Reference Voltage: Internal reference of 100mV or 1V, or externally adjustable for custom ranges.
• Input Impedance: Ultra-high input impedance (>10¹²Ω) minimizes signal loading.
• Operating Temperature Range: 0°C to +70°C (commercial grade).

Package Information

The ICL7106 is available in multiple package options to suit different assembly and space requirements:

• ICL7106CPL: 40-lead Plastic Dual In-Line Package (DIP), 0°C to +70°C.
• ICL7106RCPL: 40-lead Plastic DIP with reversed lead orientation (Note: "R" denotes reversed leads).
• ICL7106CM44: 44-lead Metric Plastic Quad Flatpack (MQFP), 0°C to +70°C.

Note: The ICL7107 variant (LED driver) shares the same package options but is intended for LED display applications.

Detailed Description

The ICL7106 integrates a dual-slope ADC architecture, which provides excellent noise rejection and accuracy. The device includes an internal voltage reference, clock oscillator, and display drivers, reducing the need for external components. The dual-slope conversion method ensures high linearity and rejection of power supply noise, making it ideal for precision applications.

The differential input allows measurement of signals relative to a reference rather than ground, improving accuracy in noisy environments. The on-chip reference can be used directly or overridden with an external reference for custom scaling. The device's low power consumption and high input impedance make it particularly suitable for battery-operated and high-impedance sensor applications.

Ordering Information

For design flexibility, the ICL7106 is offered in multiple variants:

• ICL7106CPL: Standard 40-lead DIP, commercial temperature range.
• ICL7106RCPL: 40-lead DIP with reversed pinout.
• ICL7106CM44: 44-lead MQFP for surface-mount applications.

Equivalent variants (ICL7107) with LED drive capability are also available for applications requiring LED displays.

Conclusion

The ICL7106 is a highly integrated, precision ADC solution for digital measurement systems. Its combination of low power consumption, high accuracy, and flexible display driving capabilities makes it a preferred choice for designers of portable and precision instruments. With multiple package options and variants supporting both LCD and LED displays, the ICL7106 family offers a versatile solution for a wide range of applications.