Intersil ICL7106 and ICL7107

The ICL7106 and ICL7107 are single chip digital meter solutions by the Intersil Corporation. The ICL7106 can drive a 3½-digit Liquid Crystal Display (LCD) panel without the need for additional interfacing, whilst the ICL7107 directly drives four 7-segment display modules without the need for additional driver circuitry. This IC also has a built-in Analogue to Digital Converter (ADC), seven-segment decoder, display drivers, and a clock oscillator. All of these features make a single chip solution possible. As you can see from my animated circuit diagram above, very few external components are required.

Useful Features

• Zero reading for 0 V input on all scales
• 1 pA typical input current
• ICL7106 – LCD
• lCL7107 – LED
• Low noise of less than 15 µV
• On-chip clock and reference
• Power dissipation 10 mW
• Enhanced display stability

Building a Custom Digital Meter

It is possible to design a custom meter with specifications of your choice by calculating values for the integrate resistor and capacitor provided by the very simple formulas in the manual. I built my custom meter with the largest and brightest seven-segment LED displays I could find.

When I designed and built mine, I drew the ICL7106 and ICL7107 Digital Meter Circuit first to be clear, and calculated the component values using the supplied formulas. To build a simple digital panel meter the following components are required. As you can see, just five capacitors, and five resistors are required. The component values are such as to provide a 200 mV full-scale deflection reading.

This circuit will operate on a single nine volt PP3 battery, making it an ideal solution for a bench or pocket sized meter.

The ability to scale the reading easily, and the low number of external components, makes this package an ideal solution for design of panel meters in industry.

Evaluation Kit

There is also an evaluation kit mentioned in the instruction manual, part number ICL7107EV/ Kit or the ICL7106EV/KIT, however I managed to find the main chip on eBay for £1.70 and it came directly from China.

Maximum Voltage Ratings

• ICL7106, V+ to V- 15 V
• ICL7107, V+ to GND 6 V
• ICL7107, V- to GND -9 V

This chip operates on a wide range of voltages and the internal ADC maintains accuracy.

Packages Available

The ICL7106 and the ICL7107 are available in a wide variety of packages to suit any design style. They are available in PDIP, MQFP, and COB. The Chip on Board (COB) version, shown above, is ideal for use in low cost digital meters.

For electronics enthusiasts who will be building this on prototyping board, the PDIP version is the best package to work with. This chip is available from many online electronics stores at varying prices so it is worth shopping around.

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