What is digital potentiometer (digipots)?
A digital potentiometer, also known as a digital variable resistor or a digipot, is an electronic component that mimics the functionality of a traditional mechanical potentiometer or variable resistor, but with digital control instead of physical adjustment.
A digital potentiometer replaces the mechanical sliding contact with electronic components to provide a digitally controlled resistance. It typically consists of a resistive ladder network and electronic switches that adjust the resistance value using digital signals. Digital control can be achieved through various means, such as microcontrollers, serial communication protocols (such as I2C or SPI), or direct digital inputs.
As mentioned in Fig 1, the resistor ladder is divided into segments. Each segment is connected to terminal W using a MOSFET switch. The gate of the switch decides whether the segment is shorted to W or not. The resistance of the switch can be considered as zero for simplified analysis.
What is a (mechanical) potentiometer?
A potentiometer is a three-terminal resistor with an adjustable center tap, used to control the flow of electric current. It consists of a resistive track and a sliding contact, usually operated by a knob or dial, which allows the user to vary the resistance between the end terminals and the center tap. This adjustment affects the voltage or current passing through the potentiometer.
Advantages of digital potentiometer
Digital potentiometers offer several advantages over their mechanical counterparts, including:
- Precise control: Digital potentiometers provide more precise control over the resistance value compared to mechanical potentiometers, as they can be adjusted with higher resolution and accuracy.
- Remote control: Since digital potentiometers can be controlled using digital signals, they can be easily adjusted remotely or integrated into digital systems.
- Memory and presets: Some digital potentiometers have built-in memory that allows them to retain the resistance value even when power is removed. This feature is particularly useful for applications requiring preset values or automated adjustments.
- Dynamic adjustment: Digital potentiometers can be adjusted dynamically during operation, allowing for real-time control and automation in electronic circuits.
Terminologies used in digipot
Taps
Taps are the junction where two resistors and a switch joins. The number of Taps equals the number of segments a big resistor is divided into. The largest resistance that could be obtained divided by the number of taps equals the resolution of the digit-pot.
Wiper
In a potentiometer it is the third terminal out of three where variable resistance/voltage is achieved. The other two terminals have a large fixed resistance across them.
Zero code error
This is residual resistance when there is zero code entered inside the digital potentiometer. The residual resistance expected was zero however due to some manufacturing and design limitations, there is always some residual resistance.
Applications of digital potentiometer
Digital potentiometers find applications in various electronic systems, including audio equipment, instrumentation, programmable voltage and current sources, motor control, and calibration circuits. They offer flexibility, versatility, and improved functionality compared to traditional potentiometers, especially in scenarios where precise control, automation, or remote adjustment is required.