Function Description of ICL7107CPL Chip
1. General Introduction
The ICL7107CPL is a popular, high – performance, 3 1/2 – digit analog – to – digital converter (ADC) integrated circuit produced by Intersil (now part of Renesas). It is widely used in digital voltmeters, multimeters, and other measurement and instrumentation applications due to its simplicity, accuracy, and low cost.
2. Analog – to – Digital Conversion
2.1 Resolution
The ICL7107CPL offers a 3 1/2 – digit resolution. This means it can display values from 0 to 1999, providing a sufficient level of precision for many common measurement tasks. For example, in a basic DC voltage measurement, it can accurately measure voltages with a resolution that is appropriate for general – purpose testing and monitoring.
2.2 Conversion Principle
It uses a dual – slope integrating ADC technique. In the first phase, the input voltage is integrated over a fixed period of time. Then, in the second phase, a reference voltage is integrated in the opposite direction until the integrator output returns to zero. The time taken for this second integration is proportional to the input voltage, and this time is converted into a digital value that represents the input voltage. This dual – slope method provides good noise rejection and accuracy, especially in the presence of AC noise and interference.
3. Input and Output Characteristics
3.1 Input Range
The chip has a specified input voltage range. It can measure both positive and negative DC voltages. The input range can be adjusted by external resistors, allowing for flexibility in measuring different voltage levels. For example, with appropriate resistor selection, it can be configured to measure voltages from a few millivolts up to several volts.
3.2 Output Display
The ICL7107CPL is designed to directly drive a 3 1/2 – digit seven – segment LED display. It provides all the necessary signals to light up the segments of the LED display in the correct pattern to show the measured value. The output signals are in a format that is compatible with common seven – segment displays, simplifying the design of the display circuitry.
4. Power Supply
4.1 Power Requirements
It operates on a dual – power supply system, typically requiring a positive supply voltage (+V) and a negative supply voltage (-V). The power supply voltages are usually in the range of ±5V to ±15V. This dual – power supply configuration allows for the measurement of both positive and negative input voltages and provides the necessary electrical bias for the internal circuitry of the ADC.
4.2 Power Consumption
The ICL7107CPL has relatively low power consumption, which makes it suitable for battery – powered applications. The low power consumption helps to extend the battery life of portable measurement devices.
5. Additional Features
5.1 Overload Indication
The chip has an overload indication feature. When the input voltage exceeds the maximum measurable range, it can provide an indication on the display, such as showing an “OL” (overload) symbol. This helps the user to quickly identify when the input voltage is out of the measurement range and take appropriate action, such as adjusting the measurement range or using a different measurement method.
5.2 Zero – Input Offset Adjustment
It allows for zero – input offset adjustment. This is important for ensuring accurate measurements, especially when measuring very small voltages. By adjusting the zero – input offset, the user can compensate for any inherent offset in the ADC and ensure that the measured value is accurate when the input voltage is zero.
6. Applications
6.1 Digital Voltmeters
The ICL7107CPL is most commonly used in digital voltmeters. It provides a simple and cost – effective solution for converting analog voltage signals into digital values and displaying them on a seven – segment LED display. This makes it ideal for hobbyist projects as well as professional – grade voltmeters.
6.2 Multimeters
In multimeters, which can measure various electrical quantities such as voltage, current, and resistance, the ICL7107CPL can be used as the ADC for the voltage – measurement function. Its ability to measure both positive and negative voltages and its relatively high resolution make it suitable for use in these versatile measurement instruments.
6.3 Other Instrumentation
It can also be used in other types of measurement and instrumentation applications, such as data loggers, sensor interfaces, and test equipment, where accurate analog – to – digital conversion of DC voltages is required.
