A
digital potentiometer is a digitally-controlled electronic component that mimics the analog functions of a
potentiometerA potentiometer is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used , it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment...
. It is often used for trimming and scaling analog signals by
microcontrollersA microcontroller is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timers, watchdog timer, serial and analog I/O etc. Program memory in the form of NOR flash or OTP ROM is also often included on...
. It is either built using an R-2R
integrated circuitIn electronics, an integrated circuit is a miniaturized electronic circuit that has been manufactured in the surface of a thin substrate of semiconductor material...
or a
Digital-to-analog converterIn electronics, a digital-to-analog converter is a device for converting a digital code to an analog signal ....
. A digital potentiometer is an electronic component that is often controlled by digital protocols like
I²CI²C is a multi-master serial computer bus invented by Philips that is used to attach low-speed peripherals to a motherboard, embedded system, or cellphone. The name is pronounced eye-squared-see or eye-two-see. Since the mid 1990s several competitors I²C (Inter-Integrated Circuit) is a...
and
SPIThe Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard named by Motorola that operates in full duplex mode. Devices communicate in master/slave mode where the master device initiates the data frame...
, as well as more basic Up/Down protocols. Some typical uses of digital potentiometers are in circuits requiring gain control of amplifiers (frequently
instrumentation amplifiersAn instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment...
), small-signal audio-balancing, and offset adjustment.
Sometimes this device is also referred to as an RDAC, Resistive Digital-to-Analog Converter.
Discussion
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A
digital potentiometer is a digitally-controlled electronic component that mimics the analog functions of a
potentiometerA potentiometer is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used , it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment...
. It is often used for trimming and scaling analog signals by
microcontrollersA microcontroller is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timers, watchdog timer, serial and analog I/O etc. Program memory in the form of NOR flash or OTP ROM is also often included on...
. It is either built using an R-2R
integrated circuitIn electronics, an integrated circuit is a miniaturized electronic circuit that has been manufactured in the surface of a thin substrate of semiconductor material...
or a
Digital-to-analog converterIn electronics, a digital-to-analog converter is a device for converting a digital code to an analog signal ....
. A digital potentiometer is an electronic component that is often controlled by digital protocols like
I²CI²C is a multi-master serial computer bus invented by Philips that is used to attach low-speed peripherals to a motherboard, embedded system, or cellphone. The name is pronounced eye-squared-see or eye-two-see. Since the mid 1990s several competitors I²C (Inter-Integrated Circuit) is a...
and
SPIThe Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard named by Motorola that operates in full duplex mode. Devices communicate in master/slave mode where the master device initiates the data frame...
, as well as more basic Up/Down protocols. Some typical uses of digital potentiometers are in circuits requiring gain control of amplifiers (frequently
instrumentation amplifiersAn instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment...
), small-signal audio-balancing, and offset adjustment.
Sometimes this device is also referred to as an RDAC, Resistive Digital-to-Analog Converter.
Limitations
These devices are extremely useful in the modern, digitally controlled world, but have some limitations. While quite similar to a normal potentiometer, digital potentiometers are somewhat constrained by current limits in the tens of milliamperes. Also, most, if not all digital potentiometers limit the input voltage range to the digital supply range (often 0-5VDC), so some ingenuity is often required when attempting to replace standard resistive potentiometers with digital potentiometers. Further, instead of the seemingly continuous control you can obtain from a multiturn resistive potentiometer, digital potentiometers have discrete steps in resistance. Eight-bit pots (256-steps) are most common, but you will frequently see 5, 6, and 7-bit (32, 64, 128 steps, respectively) digital potentiometers. A fourth constraint is that special logic is often required to check for zero crossing of an analog AC signal to allow the resistance value to be changed without causing an audible click in the output for audio amplifiers.
This device type appears to have been created by Xicor in 1985 now a division of
IntersilIntersil Corporation specializes in the design and manufacture of high-performance analog semiconductors for four high-growth markets — Communications, Computing, High End Consumer and Industrial.-Company history:...
and is now manufactured in many forms by several manufacturers.
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