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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Digital potentiometer</span></span>

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<p>A <b>digital potentiometer</b> (also called a <b>resistive digital-to-analog converter</b>,<sup id="cite_ref-analog_faq_1-0" class="reference"><a href="#cite_note-analog_faq-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> or informally a <b>digipot</b>) is a digitally-controlled electronic component that mimics the analog functions of a <a href="Potentiometer" title="Potentiometer">potentiometer</a>. It is often used for trimming and scaling analog signals by <a href="Microcontroller" title="Microcontroller">microcontrollers</a>.

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<div class="mw-heading mw-heading2"><h2 id="Design">Design</h2></div>

<p>A digital potentiometer is built either from a <a href="Resistor_ladder" title="Resistor ladder">resistor ladder</a> <a href="Integrated_circuit" title="Integrated circuit">integrated circuit</a> or a <a href="Digital-to-analog_converter" title="Digital-to-analog converter">digital-to-analog converter</a> although a resistor ladder construction is the more common. Every step on the resistor ladder has its own switch which can connect this step to the output terminal of the potentiometer. The selected step on the ladder determines the resistance ratio of the digital potentiometer. The number of steps is normally indicated with a bit value e.g. 8 bits equals 256 steps; 8 bits is the most common, but resolutions between 5 and 10 bits (32 to 1024 steps) are available.<sup id="cite_ref-ad5207_2-0" class="reference"><a href="#cite_note-ad5207-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> A digital potentiometer uses protocols like <a href="I%C2%B2C" title="I²C">I²C</a> or a <a href="Serial_Peripheral_Interface" title="Serial Peripheral Interface">Serial Peripheral Interface</a> bus for signalling; some use simpler up/down protocols. Typical uses of digital potentiometers are in circuits requiring gain control of amplifiers (frequently <a href="Instrumentation_amplifier" title="Instrumentation amplifier">instrumentation amplifiers</a>), small-signal audio-balancing, and offset adjustment.

</p><p>The resistor material is usually <a href="Polysilicon" class="mw-redirect" title="Polysilicon">polysilicon</a> or thin-film .<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

</p><p>Most digital potentiometers use only volatile memory, which means they forget their position when they are powered down (on power up they will report a default value, often their midpoint value) - when these are used, their last position may be stored by the microcontroller or <a href="FPGA" class="mw-redirect" title="FPGA">FPGA</a> to which they are interfaced. Some digipots do include their own non-volatile storage,<sup id="cite_ref-ds1855_4-0" class="reference"><a href="#cite_note-ds1855-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> so their default reading on power up will be the same as they showed before they were powered down.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Limitations">Limitations</h2></div>

<p>While quite similar to normal potentiometers, digital potentiometers are constrained by current limit in the range of tens of milliamperes. Also, most digital potentiometers limit the voltage range on the two input terminals (of the resistor) to the digital supply range (e.g. 0–5 VDC), so additional circuitry may be required to replace a conventional potentiometer, (although digital potentiometers with separate dual supply analog voltages are also available.)<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Further, instead of the seemingly continuous control that can be obtained from a multiturn resistive potentiometer, digital potentiometers have discrete steps in resistance.

</p><p>Another 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. (Schematic needed)

</p><p>Volatile digital potentiometers also differ from electro-mechanical ones in that on power up, the resistance will default to (possibly) a different value after a power cycle. Similarly, their resistance is only valid when the correct DC supply voltage is present. When voltage is removed, the resistance between the two end points and the (nominal) wiper are undefined. In an operational amplifier circuit, the off-state impedance of a real potentiometer can help stabilize the DC operating point of the circuit during the power-up stage. This may not be the case when a digital potentiometer is used.

</p><p>Both electro-mechanical and digital potentiometers generally have poor tolerances (typically ±20%),<sup id="cite_ref-mchip1080a_7-0" class="reference"><a href="#cite_note-mchip1080a-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> poor temperature coefficients<sup id="cite_ref-adtempco_8-0" class="reference"><a href="#cite_note-adtempco-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> (up to many hundreds of ppm per degree C),<sup id="cite_ref-adtempco_8-1" class="reference"><a href="#cite_note-adtempco-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> and a stop resistance that is typically about 0.5-1% of the full scale resistance. Note that stop resistance is the residual resistance when the terminal to wiper resistance is set to the minimum value.

</p><p>With a digital potentiometer, the resistance might be depended on supply voltage.<sup id="cite_ref-mchip1080a_7-1" class="reference"><a href="#cite_note-mchip1080a-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup>

</p><p>Digital potentiometer have a limited band width due to parasitic capacitance in device. Parts with lower end-to-end resistance typically have a greater band width.

</p><p>The <a href="Transmission_gate" title="Transmission gate">transmission gate</a>/switching element in the digital potentiometer cause harmonic distortions.

</p><p>A multiplying <a href="Digital-to-analog_converter" title="Digital-to-analog converter">DAC</a> used as a digital potentiometer can eliminate most of these limitations.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Typically a signal span of +15V to -15V is possible, with 16 bit control, i.e. 65535 discrete set points, and drift and non-linearity are negligible. However a DAC has to be initialised each time the system is powered on, which is typically done by software in an embedded microcontroller. A multiplying DAC can not be directly used as a rheostat (2 wire connection), but in that mode a digipot performs badly anyway, due to its temperature coefficient and resistance tolerance.

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<div class="mw-heading mw-heading2"><h2 id="Applications">Applications</h2></div>

<ul><li>LCD-contrast/brightness</li>

<li>Sensor calibration</li>

<li>Digital volume control</li>

<li>Programmable comparators</li>

<li>Programmable low/high-pass filters</li></ul>

<div class="mw-heading mw-heading2"><h2 id="Alternatives">Alternatives</h2></div>

<ul><li><a href="Motorized_potentiometer" title="Motorized potentiometer">Motorized potentiometer</a></li></ul>

<ul><li><a href="Console_automation" class="mw-redirect" title="Console automation">Console automation</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110907012735/http://www.analog.com/en/technical-documentation/frequently-and-rarely-asked-questions/resources/digital-to-analog-converters/digital-potentiometers/listing.html">"Digital potentiometers - frequently asked questions"</a>. <a href="Analog_Devices" title="Analog Devices">Analog Devices</a>. Archived from <a rel="nofollow" class="external text" href="http://www.analog.com/en/technical-documentation/frequently-and-rarely-asked-questions/resources/digital-to-analog-converters/digital-potentiometers/listing.html">the original</a> on 2011-09-07.</cite></span>

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<cite class="citation techreport cs1">"Digital Potentiometer Family Selection Guide". <a rel="nofollow" class="external text" href="http://www.analog.com/static/imported-files/data_sheets/AD5207.pdf"><i>AD5207 - 2-channel 256-position digital potentiometer - datasheet</i></a> <span class="cs1-format">(PDF)</span> (Technical report). <a href="Analog_Devices" title="Analog Devices">Analog Devices</a>.</cite></span>

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<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.analog.com/en/education/education-library/webcasts/digital-potentiometers-where-and-how-to-use.html">"Digital Potentiometers - Where and How to Use - Education"</a>. <i>Analog Devices</i>. 3 October 2014<span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2023</span>.</cite></span>

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<li id="cite_note-ds1855-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-ds1855_4-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.analog.com/en/products/ds1855.html">"DS1855 Dual Nonvolatile Digital Potentiometer and Secure Memory"</a>. <i>Analog Devices</i>. 5 October 2001<span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2023</span>.</cite></span>

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<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.analog.com/media/en/technical-documentation/data-sheets/DS1855.pdf">"Dual Nonvolatile Digital Potentiometer and Secure Memory"</a> <span class="cs1-format">(PDF)</span>. <i>analog.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2023</span>.</cite></span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ww1.microchip.com/downloads/en/DeviceDoc/20005207B.pdf">"7/8-Bit Single, +36V (±18V) Digital POT with SPI Serial Interface and Volatile Memory"</a> <span class="cs1-format">(PDF)</span>. <i>Microchip</i><span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2023</span>.</cite></span>

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<li id="cite_note-mchip1080a-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-mchip1080a_7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-mchip1080a_7-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ww1.microchip.com/downloads/en/Appnotes/01080a.pdf">"Understanding Digital Potentiometer Resistor Variations"</a> <span class="cs1-format">(PDF)</span>. <i>Microchip</i><span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2023</span>.</cite></span>

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<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.edn.com/multiplying-dac-makes-programmable-resistor/">"Multiplying DAC makes programmable resistor"</a>. <i>EDN</i>. 24 June 1999<span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2023</span>.</cite></span>

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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://www.resistorguide.com/digital-potentiometer/">Digital potentiometer - the Resistor Guide</a></li>

<li><a rel="nofollow" class="external text" href="https://www.renesas.com/br/en/www/doc/application-note/an1158.pdf">Designing with Intersil Digitally Controlled Potentiometers (XDCPs)</a></li></ul></div><div><div class="zim-footer">

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