What Is a Reference IC?
A reference IC is an electronic component that outputs a reference voltage for operating an electronic circuit. Such electronic circuits are also sometimes called reference circuits or reference voltage sources.
The performance of a reference IC includes the initial accuracy of the output reference voltage, stability against fluctuations in supply voltage (called line regulation), stability against load regulation, stability against changes in ambient temperature (called temperature drift), and stability against long-term use (called long-term drift). The reference IC is required to maintain stable voltage output with high accuracy on the order of ppm (0.0001%).
Uses of Reference ICs
Reference ICs are used in a variety of electronic circuits that require a reference voltage. In power supply control circuits, the output voltage is compared to a reference voltage to maintain a constant output voltage; in AD and DA converters, the input voltage is compared to a reference voltage to convert it to an appropriate output. In a voltage detector, the detection decision is made by comparison with a reference voltage.
Therefore, the performance of these electronic circuits is affected by the performance of the reference IC. Especially in the fields of science, medicine, automotive, military, aviation, and space, reference ICs with high accuracy are required.
Principle of Reference ICs
There are two types of reference IC configurations: shunt type and series type.
The shunt type consists of two terminals, the reference output, and ground, and is controlled to maintain a constant voltage drop regardless of the current flowing between the two terminals. When used, the IC is connected in parallel to the load, and an external resistor is connected between the power supply and the reference output. The current flowing through the IC varies with the supply voltage and load, but the voltage at the reference output is kept constant by the control of the IC.
The series type consists of three pins: power supply input, reference output, and ground, and when used, the IC is connected in series between the power supply and the load. The reference output is controlled to maintain a constant voltage by varying the internal resistance of the IC in response to variations in supply voltage or load.
The most commonly used method today is the bandgap reference. By matching a voltage with a positive temperature coefficient with a voltage with a negative temperature coefficient, a stable voltage output can be maintained over temperature variations.
When using a reference IC, it is necessary to properly select one that provides the performance required for the application, including not only accuracy and stability, but also start-up settling time and noise characteristics.