ICL7136

ICL7136: High Performance, Low Power 3½ Digit A/D Converter

Overview

The Harris ICL7136 is a high-performance, low-power 3½ digit analog-to-digital (A/D) converter designed for precision measurement applications. It integrates a complete A/D conversion system, including a seven-segment decoder, display driver, internal reference, and clock circuitry. The ICL7136 is specifically optimized for interfacing with liquid crystal displays (LCDs) and features a multiplexed backplane drive, making it ideal for portable and battery-powered instruments. Its counterpart, the ICL7137, is designed for LED displays, offering flexibility for different display requirements.

This device is a drop-in replacement for the ICL7126, requiring no design modifications, and is available in multiple package options to suit various assembly needs. With ultra-low input current and true differential inputs, the ICL7136 ensures high accuracy and reliability in demanding measurement environments.

Features

• First Reading Overrange Recovery: Recovers from overrange conditions in a single conversion period.
• Guaranteed Zero Reading: Provides a true zero reading for 0V input across all scales.
• True Polarity at Zero: Ensures precise null detection for accurate measurements near zero.
• Ultra-Low Input Current: Typical input current of just 1pA minimizes loading effects.
• True Differential Input and Reference: Supports direct differential measurements for improved noise immunity.
• Display Drive Options:
  • ICL7136: LCD drive with multiplexed backplane.
  • ICL7137: Direct LED drive capability.
• Low Noise: Less than 15µV peak-to-peak noise for high-resolution measurements.
• Integrated Clock and Reference: On-chip components reduce external part count.
• No Additional Active Circuits Required: Simplifies system design and reduces cost.
• Low Power Consumption: Operates at less than 1mW, ideal for battery-powered applications.
• Package Options: Available in small outline surface-mount and through-hole packages.

Applications

The ICL7136 is widely used in precision measurement systems where low power and high accuracy are critical. Key applications include:

• Portable Instrumentation: Digital multimeters, panel meters, and handheld test equipment.
• Battery-Powered Devices: Due to its low power consumption, it is ideal for portable and field-deployable systems.
• Industrial Process Control: Provides accurate voltage and current measurements in control systems.
• Medical Equipment: Used in diagnostic devices requiring high-resolution analog measurements.
• Automotive Testing: Suitable for sensors and monitoring systems in automotive applications.
• Consumer Electronics: Integrated into scales, thermometers, and other measurement devices.

Electrical Characteristics

The ICL7136 operates under the following key electrical specifications:

• Supply Voltage: Typically operates from a single +5V supply.
• Input Voltage Range: Differential input range of ±2V, supporting bipolar measurements.
• Conversion Rate: Up to 3 conversions per second, adjustable via external clock components.
• Linearity Error: ±1 count maximum over the full temperature range.
• Input Impedance: Greater than 10¹²Ω, minimizing signal loading.
• Reference Voltage: Internal reference of 1V, with options for external reference adjustment.
• Operating Temperature Range: 0°C to +70°C for commercial-grade devices.

Package Information

The ICL7136 is available in multiple package configurations to accommodate different assembly and space requirements:

• ICL7136CPL: 40-lead Plastic DIP (Dual In-line Package), commercial temperature range (0°C to +70°C).
• ICL7136RCPL: 40-lead Plastic DIP with reversed lead orientation (Note: "R" indicates reversed leads).
• ICL7136CM44: 44-lead Metric Plastic Quad Flatpack (MQFP), suitable for surface-mount applications.

For the ICL7137 (LED drive variant), the same package options are available, ensuring compatibility across display types.

Additional Notes

The ICL7136 is designed for ease of integration, requiring minimal external components. Its robust architecture ensures reliable performance in noisy environments, while its low power consumption extends battery life in portable applications. Designers should refer to the datasheet for detailed application circuits, timing diagrams, and layout recommendations to optimize performance.

File Number 3086, January 1994 – Harris Semiconductor