Digital Potentiometers Information

Digital potentiometers are three-terminal resistors with an adjustable center connection. To set the output resistance, a digital signal is sent through an electrical interface. There are two main configurations for digital potentiometers: single resistor and resistor chip array. Single resistors are standard, passive resistors with a single resistance value. Resistor chip arrays contain several resistors housed in a single package. For both digital potentiometer configurations, specifications include current rating, resistance range, temperature coefficient of resistance (TCR), tolerance, number of steps or taps, operating direct current (DC) voltage, and operating temperature. For resistor chip arrays, the number of resistors in the package is also an important consideration. 

Resistance taper and wiper memory are additional parameters to consider when selecting digital potentiometers. There are two choices for resistance taper: linear and log (audio). Digital potentiometers with a linear taper provide an equal change in resistance per unit of rotation. By contrast, devices with a log or audio taper provide a logarithmic change in resistance per unit of rotation. Wiper memory for digital potentiometers is either volatile or non-volatile. Volatile memory is lost when power is turned off. Non-volatile memory is retained even when power is removed. 

Digital potentiometers differ in terms of categories, applications, and features. Categories include precision resistors and telecom resistors. Precision resistors have a very low TCR and a very low tolerance value. Telecom resistors are designed for telecommunications devices such as mobile phones and two-way radios. In terms of applications, digital potentiometers for aerospace, audio / video (AV), automotive, and medical applications are commonly available. Industrial resistors are suitable for a variety of heavy-duty, industrial applications. General-use devices are used in consumer products, computers or disk drives, and to provide over-current protection. Some digital potentiometers are water-cooled or provide electrostatic discharge (ESD) protection. Others feature a fireproof case, an electrically isolated case, or have a non-flame coating.  

Digital potentiometers that are sold in European Union (EU) nations must meet three important directives: Restriction of Hazardous Substances (RoHS), End-of-Life Vehicles (ELV), and Waste Electrical and Electronics Equipment (WEEE). RoHS requires all manufactures of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether. Similarly, digital potentiometers that are ELV-compliant contain only minimal levels of mercury, cadmium and lead. Suppliers that comply with WEEE are responsible for financing the collection, treatment, recycling and recovery of their products.

• Communicating with Daisy Chained MCP42XXX Digital Potentiometers
  The MCP41XXX and MCP42XXX family of digital potentiometers allow for daisy chaining of multiple devices on a single SPI? bus. It is possible to communicate to multiple devices using one 3-wire data bus (CS, CLK and DATA), by connecting the SO pin on one device to the SI pin of the next device...
• Interfacing Microchip's MCP41XXX and MCP42XXX Digital Potentiometers to Motorola?s 68HC12 Microcontroller
  The MCP41XXX and MCP42XXX family of digital potentiometers communicate using a standard 3-wire SPI compatible interface. This application note will cover communication between these devices and the Motorola 68HC12 family of microcontrollers. Specifically, the MC68HC912B32 evaluation board was used...
• Comparing Digital Potentiometers to Mechanical Potentiometers
  in this application note are the mechanical potentiometer (also called a trimmer potentiometer) and the digital potentiometer. Comparing Digital Potentiometers to Mechanical Potentiometers AN219. Comparing Digital Potentiometers to Mechanical. Potentiometers. Earlier mechanical potentiometers were built...