1 A Low-Dropout Regulator UMW - AMS1117 - readme.html

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<div class=ident><h1>AMS1117</h1><span class=mfr>UMW &middot; Youtai Semiconductor</span><span class=badge>1 A LDO &middot; UMW</span></div>
<p class=oneline>UMW's <b>second-source</b> AMS1117: a positive <b>1 A low-dropout linear voltage regulator</b> with a typical dropout of <b>1.2 V at 1 A</b>, in fixed 1.2 / 1.5 / 1.8 / 2.5 / 3.3 / 5.0 V versions or an adjustable version set by two resistors around a 1.25 V reference. Output tolerance is 1.5 % on every fixed version except 1.2 V, which is 2 %. Includes thermal shutdown and current limiting, and takes up to <b>18 V</b> in. Offered in SOT-223-3L, TO-252-2L and SOT-89-3L.</p>
<div class=sib><b>This page is the UMW / Youtai Semiconductor part only.</b> Everything below comes from the UMW datasheet and applies to UMW-branded silicon. The part number originated at Advanced Monolithic Systems, whose version has a <b>different voltage lineup, a different third package and materially different limits</b>. If your BOM says AMS, use <a href="https://wiki.adom.inc/adom/ams-ams1117">1 A Low-Dropout Regulator AMS - AMS1117</a> instead.</div>
<div class=metarow>
<span class=m>Output <b>1 A</b></span><span class=m>Dropout <b>1.30 V max @ 1 A</b></span><span class=m>V<sub>IN</sub> <b>18 V max</b></span>
<span class=m>Versions <b>6 fixed + ADJ</b></span><span class=m>Packages <b>SOT-223 · TO-252 · SOT-89</b></span><span class=m>Pins <b>3</b></span>
</div>

<h2>At a glance</h2>
<div class=grid>
<div class=card><div class="k" style="color:#00b8b1">Output current</div><div class=v>1 A</div><div class=s>Current limit 2.1 A min &middot; 2.5 A max</div></div>
<div class=card><div class="k" style="color:#28c3d4">Dropout</div><div class=v>1.30 V max</div><div class=s>1.20 V typ at the full 1 A</div></div>
<div class=card><div class="k" style="color:#4fb7f0">Fixed outputs</div><div class=v>6 versions</div><div class=s>1.2 &middot; 1.5 &middot; 1.8 &middot; 2.5 &middot; 3.3 &middot; 5.0 V</div></div>
<div class=card><div class="k" style="color:#64abff">Adjustable</div><div class=v>1.25 V ref</div><div class=s>V<sub>OUT</sub> = V<sub>REF</sub>(1 + R2/R1) + I<sub>ADJ</sub>R2</div></div>
<div class=card><div class="k" style="color:#8c6bf7">Packages</div><div class=v>3 options</div><div class=s>SOT-223-3L &middot; TO-252-2L &middot; SOT-89-3L</div></div>
<div class=card><div class="k" style="color:#a98bf9">Input voltage</div><div class=v>18 V max</div><div class=s>12 V recommended operating maximum</div></div>
</div>

<h2>Specifications</h2>
<div>
<div class=spec><span class=lbl>Output current</span><span>1 A</span></div>
<div class=spec><span class=lbl>Fixed output voltages</span><span>1.2 / 1.5 / 1.8 / 2.5 / 3.3 / 5.0 V. Also available adjustable</span></div>
<div class=spec><span class=lbl>Output accuracy</span><span>1.5 % on 1.5 / 1.8 / 2.5 / 3.3 / 5.0 V and the adjustable version &middot; <b>2 % on the 1.2 V version</b></span></div>
<div class=spec><span class=lbl>Reference voltage</span><span>1.250 V typ: 1.231 to 1.268 V at 25 &deg;C, 1.225 to 1.275 V over the full range</span></div>
<div class=spec><span class=lbl>Dropout voltage</span><span>1.00 typ / 1.20 max at 100 mA &middot; 1.05 / 1.25 at 500 mA &middot; <b>1.20 / 1.30 at 1 A</b></span></div>
<div class=spec><span class=lbl>Input voltage</span><span>18 V absolute maximum &middot; 12 V recommended operating maximum</span></div>
<div class=spec><span class=lbl>Line regulation</span><span>9 mV typ, 18 mV max (V<sub>IN(min)</sub> &le; V<sub>IN</sub> &le; 12 V, I<sub>OUT</sub> = 10 mA)</span></div>
<div class=spec><span class=lbl>Load regulation</span><span>10 mV typ, 18 mV max (10 mA &le; I<sub>OUT</sub> &le; 1 A)</span></div>
<div class=spec><span class=lbl>Current limit</span><span><b>2.1 A min, 2.5 A max</b></span></div>
<div class=spec><span class=lbl>Quiescent current</span><span>5 mA typ, 10 mA max (4.25 V &le; V<sub>IN</sub> &le; 6.5 V)</span></div>
<div class=spec><span class=lbl>Ripple rejection</span><span>60 dB min, 75 dB typ (120 Hz, V<sub>IN</sub> &minus; V<sub>OUT</sub> = 3 V, 1 V<sub>PP</sub> ripple)</span></div>
<div class=spec><span class=lbl>Adjust pin current</span><span>60 &micro;A typ, 120 &micro;A max &middot; change 0.2 &micro;A typ, 5 &micro;A max</span></div>
<div class=spec><span class=lbl>Output temperature stability</span><span>0.3 % typ</span></div>
<div class=spec><span class=lbl>Temperature stability</span><span>0.5 % typ</span></div>
<div class=spec><span class=lbl>Long term stability</span><span>0.3 % typ (1000 h at 125 &deg;C)</span></div>
<div class=spec><span class=lbl>RMS output noise</span><span>0.003 % of V<sub>OUT</sub> (10 Hz to 10 kHz)</span></div>
<div class=spec><span class=lbl>Protection</span><span>Current limiting + thermal shutdown at <b>150 &deg;C</b> typ</span></div>
<div class=spec><span class=lbl>Thermal resistance R<sub>&theta;JA</sub></span><span>SOT-223-3L <b>88 &deg;C/W</b> &middot; TO-252-2L <b>86 &deg;C/W</b> &middot; SOT-89-3L <b>102 &deg;C/W</b></span></div>
<div class=spec><span class=lbl>ESD tolerance</span><span>2000 V minimum</span></div>
<div class=spec><span class=lbl>Operating junction temp</span><span>&minus;40 to +125 &deg;C recommended &middot; 150 &deg;C absolute maximum</span></div>
<div class=spec><span class=lbl>Storage temperature</span><span>&minus;65 to +150 &deg;C</span></div>
<div class=spec><span class=lbl>Soldering</span><span>Lead temperature 260 &deg;C, 5 s</span></div>
<div class=spec><span class=lbl>Required output cap</span><span>22 &micro;F tantalum covers all cases; smaller values work without adjust-pin bypassing</span></div>
</div>

<h2>Symbol &amp; footprint</h2>
<div class=viewers2>
<div><div class=vh>Schematic symbol: hover a pin for its function</div>
<iframe class=vframe height=520 loading=lazy title="AMS1117 schematic symbol" src="https://wiki.adom.inc/api/v1/pages/adom/umw-ams1117/files/viewer-symbol.html"></iframe></div>
<div><div class=vh>PCB footprint: switch package bottom-right (SOT-223 / TO-252 / SOT-89)</div>
<iframe class=vframe height=520 loading=lazy title="AMS1117 footprint (SOT-223 / TO-252 / SOT-89)" src="https://wiki.adom.inc/api/v1/pages/adom/umw-ams1117/files/viewer-footprints.html"></iframe></div>
</div>

<h2>Pin map <span style="color:var(--text-2);font-weight:400;font-size:14px">3 terminals, identical across all three packages</span></h2>
<div class=callout>The pinout is the same on SOT-223-3L, TO-252-2L and SOT-89-3L, and <b>on all three the metal tab is V<sub>OUT</sub></b>, internally bonded to pin 2. It is the heat path, so it must be soldered to a copper pour on the output net, never to ground. All three footprints shipped here carry the tab as pad 2.</div>
<div class=pinwrap>
<div class=pg><div class=pgh style="border-color:#00b8b1"><span class=dot style="background:#00b8b1"></span>All packages<span class=ct>3 + tab</span></div><table class=pt><tbody>
<tr><td class=pn>1</td><td class=nm>GND/ADJ</td><td class=fx>Ground on fixed versions; adjust (feedback) node on the adjustable version</td></tr>
<tr><td class=pn>2</td><td class=nm>VOUT</td><td class=fx>Regulated output. Also the metal tab</td></tr>
<tr><td class=pn>3</td><td class=nm>VIN</td><td class=fx>Input supply voltage, 18 V max</td></tr>
<tr><td class=pn>n/a</td><td class=nm>TAB</td><td class=fx>Thermal pad, bonded to pin 2 (V<sub>OUT</sub>)</td></tr>
</tbody></table></div>
<div class=pg><div class=pgh style="border-color:#8c6bf7"><span class=dot style="background:#8c6bf7"></span>Topside marking<span class=ct>3</span></div><table class=pt><tbody>
<tr><td class=pn></td><td class=nm>SOT-223-3L</td><td class=fx><code>AMS1117</code> / <code>3.3</code> + lot code</td></tr>
<tr><td class=pn></td><td class=nm>TO-252-2L</td><td class=fx><code>1117 CD</code> / <code>3.3</code> + lot code</td></tr>
<tr><td class=pn></td><td class=nm>SOT-89-3L</td><td class=fx><code>STK17</code> / <code>3.3</code> + lot code. Note the different prefix</td></tr>
</tbody></table></div>
</div>

<h2>Internal structure</h2>
<div class=callout>The pass element is a <b>single NPN transistor driven by a PNP</b>, so dropout is set by V<sub>DROP</sub> = V<sub>BE</sub> + V<sub>SAT</sub>. Which is why this family cannot get below about 1 V and why dropout rises with load. Fixed and adjustable versions are the <b>same die</b>: an on-chip link selection (F1 and F2 connected with A open for fixed, A connected with F1 and F2 open for adjustable) either wires the internal divider to the output or brings the feedback node out on pin 1.</div>

<h2>Component variants</h2>
<div class=callout>All variants are the same silicon. The order code carries the <b>package</b> and the <b>output voltage</b> independently. Unlike the AMS original, UMW spells the adjustable version out as <code>-ADJ</code> rather than leaving the suffix blank.</div>
<div class=occode>
<div class=ocbig><span style="color:#e6edf3">AMS1117</span><span style="color:#8c6bf7">CD</span><span style="color:#00e6dc">-3.3</span><span style="color:#64abff">S</span></div>
<div class=oclegend>
<div class=ocitem><div class=octop><span class=sw style="background:#8b949e"></span><b style="color:#e6edf3">AMS1117</b></div><div class=ocdesc>base part: 1 A LDO</div></div>
<div class=ocitem><div class=octop><span class=sw style="background:#8c6bf7"></span><b style="color:#a98bf9">CD / blank</b></div><div class=ocdesc><code>CD</code> = TO-252-2L &middot; blank = SOT-223-3L</div></div>
<div class=ocitem><div class=octop><span class=sw style="background:#00e6dc"></span><b style="color:#00e6dc">-3.3 / -ADJ</b></div><div class=ocdesc>fixed output voltage, or <code>-ADJ</code> for the adjustable version</div></div>
<div class=ocitem><div class=octop><span class=sw style="background:#64abff"></span><b style="color:#8fc6ff">S</b></div><div class=ocdesc>trailing <code>S</code> selects SOT-89-3L</div></div>
</div>
</div>
<div class=vgrid>
<div class=vcard>
<h3>SOT-223-3L<span class=chip style="background:rgba(139,148,158,.18);color:#8b949e">no letter</span></h3>
<div class=sub>5.90 to 6.70 &times; 3.90 &plusmn;0.30 mm body, 1.60 &plusmn;0.15 mm height &middot; 2.30 mm TYP lead pitch &middot; 4.60 &plusmn;0.15 mm lead span &middot; tab = V<sub>OUT</sub></div>
<div class=oc><b>Fixed:</b> <code>AMS1117-1.2</code> <code>-1.5</code> <code>-1.8</code> <code>-2.5</code> <code>-3.3</code> <code>-5.0</code></div>
<div class=oc><b>Adjustable:</b> <code>AMS1117-ADJ</code></div>
<div class=oc>R<sub>&theta;JA</sub> <b>88 &deg;C/W</b></div>
</div>
<div class=vcard>
<h3>TO-252-2L <code style="font-size:13px">CD</code></h3>
<div class=sub>6.40 to 6.70 &times; 6.00 to 6.30 mm body, 2.20 to 2.30 mm height &middot; 2.20 to 2.40 mm lead pitch &middot; tab = V<sub>OUT</sub></div>
<div class=oc><b>Fixed:</b> <code>AMS1117CD-1.2</code> <code>-1.5</code> <code>-1.8</code> <code>-2.5</code> <code>-3.3</code> <code>-5.0</code></div>
<div class=oc><b>Adjustable:</b> <code>AMS1117CD-ADJ</code></div>
<div class=oc>R<sub>&theta;JA</sub> <b>86 &deg;C/W</b>. The best thermal option</div>
</div>
<div class=vcard>
<h3>SOT-89-3L <code style="font-size:13px">S</code></h3>
<div class=sub>4.50 &plusmn;0.30 &times; 2.45 &plusmn;0.30 mm body, 1.50 &plusmn;0.20 mm thick &middot; 3.00 mm BSC lead pitch &middot; tab = V<sub>OUT</sub></div>
<div class=oc><b>Fixed:</b> <code>AMS1117-1.2S</code> <code>-1.5S</code> <code>-1.8S</code> <code>-2.5S</code> <code>-3.3S</code> <code>-5.0S</code></div>
<div class=oc><b>Adjustable:</b> <code>AMS1117-ADJS</code></div>
<div class=oc>R<sub>&theta;JA</sub> <b>102 &deg;C/W</b> &middot; smallest footprint, marked <code>STK17</code></div>
</div>
</div>
<p style="color:var(--text-2);font-size:13.5px;margin:14px 0 0">The AMS original offers an <b>8-lead SOIC</b> in place of SOT-89, and a <b>2.85 V</b> version that UMW does not carry. See the <a href="https://wiki.adom.inc/adom/ams-ams1117">AMS page</a>.</p>

<h2>Output voltage versions</h2>
<p style="color:var(--text-2);font-size:14px;margin:0 0 10px">Two limit sets per version: the tighter one at T<sub>J</sub> = 25 &deg;C with I<sub>OUT</sub> = 10 mA, and the wider one over the full load and line range (0 or 10 mA &le; I<sub>OUT</sub> &le; 1 A).</p>
<table class=vt><thead><tr><th>Version</th><th>V<sub>OUT</sub> typ</th><th>Min to max at 25 &deg;C</th><th>Min to max, full range</th><th>Test V<sub>IN</sub></th><th>Accuracy</th></tr></thead><tbody>
<tr><td>AMS1117-1.2</td><td>1.200 V</td><td>1.176 to 1.224 V</td><td>1.152 to 1.248 V</td><td>3.2 V</td><td><b>2 %</b></td></tr>
<tr><td>AMS1117-1.5</td><td>1.500 V</td><td>1.477 to 1.522 V</td><td>1.470 to 1.530 V</td><td>3.5 V</td><td>1.5 %</td></tr>
<tr><td>AMS1117-1.8</td><td>1.800 V</td><td>1.773 to 1.827 V</td><td>1.746 to 1.854 V</td><td>3.8 V</td><td>1.5 %</td></tr>
<tr><td>AMS1117-2.5</td><td>2.500 V</td><td>2.462 to 2.538 V</td><td>2.450 to 2.550 V</td><td>4.5 V</td><td>1.5 %</td></tr>
<tr><td>AMS1117-3.3</td><td>3.300 V</td><td>3.250 to 3.349 V</td><td>3.235 to 3.365 V</td><td>5.0 V</td><td>1.5 %</td></tr>
<tr><td>AMS1117-5.0</td><td>5.000 V</td><td>4.925 to 5.075 V</td><td>4.900 to 5.100 V</td><td>7.0 V</td><td>1.5 %</td></tr>
<tr><td>AMS1117-ADJ</td><td>1.250 V ref</td><td>1.231 to 1.268 V</td><td>1.225 to 1.275 V</td><td>V<sub>OUT</sub>+2 V</td><td>1.5 %</td></tr>
</tbody></table>
<div class=callout style="margin-top:14px"><b>Datasheet inconsistency worth knowing.</b> The Features bullet on page 1 claims "1.5 % output accuracy" for a list that <b>includes</b> 1.2 V, but the General Description on the same page says 1.2 V is <b>2 %</b>, and the Electrical Characteristics table settles it: 1.176 to 1.224 V at 25 &deg;C is &plusmn;2.0 %, where every other version works out to &plusmn;1.5 %. Design to <b>2 %</b> on the 1.2 V part.</div>

<h2>Assets</h2>
<p style="color:var(--text-2);font-size:14px;margin:0 0 10px">KiCad symbol, all three footprints and matching 3D models, plus the canonical <b>adom-lbr JSON</b> the rest is generated from.</p>
<table class=at><tbody>
<tr><td class=tool style="color:#00b8b1">KiCad symbol</td><td><a href=ams1117.kicad_sym>ams1117.kicad_sym</a> (3-pin, all three packages)</td></tr>
<tr><td class=tool style="color:#28c3d4">KiCad footprints</td><td><a href=ams1117-sot223.kicad_mod>AMS1117_SOT-223</a> &middot; <a href=ams1117-to252.kicad_mod>AMS1117_TO-252</a> &middot; <a href=ams1117-sot89.kicad_mod>AMS1117_SOT-89</a></td></tr>
<tr><td class=tool style="color:#64abff">3D models</td><td>SOT-223 <a href=ams1117-sot223.step>.step</a> / <a href=ams1117-sot223.glb>.glb</a> &middot; TO-252 <a href=ams1117-to252.step>.step</a> / <a href=ams1117-to252.glb>.glb</a> &middot; SOT-89 <a href=ams1117-sot89.step>.step</a> / <a href=ams1117-sot89.glb>.glb</a></td></tr>
<tr><td class=tool style="color:#8c6bf7">Canonical</td><td><a href=ams1117.adom-lbr.json>ams1117.adom-lbr.json</a></td></tr>
<tr><td class=tool style="color:#484f58">Fusion 360 / EAGLE</td><td class=na>Not available yet</td></tr>
<tr><td class=tool style="color:#484f58">Altium</td><td class=na>Not available yet</td></tr>
</tbody></table>

<h2>Implementation</h2>
<ul class=ul>
<li><a href="https://wiki.adom.inc/adom/large-automotive-eth-switch-molecule"><b>Large Automotive Eth Switch Molecule</b></a>. An AMS1117-1.2 supplies the KSZ9131 gigabit PHY 1.2 V core rail (U902) from the board's 3.3 V rail. 1.2 V is a UMW-only version, so this is a UMW part.</li>
<li><a href="https://wiki.adom.inc/adom/ams-ams1117"><b>1 A Low-Dropout Regulator AMS - AMS1117</b></a>. The original Advanced Monolithic Systems part. Adds 2.85 V and an 8-lead SOIC; drops 1.2 V and SOT-89.</li>
</ul>

<h2>Application notes</h2>
<ul class=ul>
<li><b>Typical circuit is 10 &micro;F in, 22 &micro;F out.</b> The output capacitor is part of the device's stability, not just decoupling. 22 &micro;F tantalum covers every case including a bypassed adjust pin; without adjust-pin bypassing, smaller values work, but the datasheet is explicit that stability degrades as output current rises.</li>
<li><b>Dropout is load-dependent, and specified all the way to 1 A</b>: 1.20 V max at 100 mA rising to 1.30 V max at the full amp. Size the input rail from the 1 A figure unless the load is genuinely light.</li>
<li><b>Current limit is high.</b> At 2.1 to 2.5 A this part will happily push well past its 1 A rating into a fault before folding back, so the thermal path, not the current limit, is what protects the board. Thermal shutdown is at 150 &deg;C.</li>
<li><b>Copper is the heat sink.</b> P<sub>D(max)</sub> = (T<sub>J(max)</sub> &minus; T<sub>amb</sub>) / R<sub>&theta;JA</sub>, and the datasheet is clear that R<sub>&theta;JA</sub> depends on mounting technique. The 88 / 86 / 102 &deg;C/W figures are a starting point, not a guarantee.</li>
<li><b>Adjustable output:</b> V<sub>OUT</sub> = V<sub>REF</sub> &times; (1 + R2/R1) + I<sub>ADJ</sub> &times; R2, with V<sub>REF</sub> = 1.25 V and I<sub>ADJ</sub> &asymp; 60 &micro;A.</li>
</ul>

<h2>Datasheet</h2>
<iframe class=dsheet loading=lazy title="AMS1117 datasheet (UMW / Youtai Semiconductor)" src="https://wiki.adom.inc/api/v1/pages/adom/umw-ams1117/files/docs/ams1117-datasheet-umw.pdf"></iframe>
<p style="margin:8px 0 0;font-size:13px"><a href=docs/ams1117-datasheet-umw.pdf>Download the full datasheet (PDF)</a> &middot; UMW (Youtai Semiconductor), <i>AMS1117 1 A LDO Voltage Regulator</i> &middot; <a href="https://www.umw-ic.com">umw-ic.com</a></p>

<h2>Provenance</h2>
<ul class=ul>
<li><b>Every electrical number on this page</b> is read from the UMW / Youtai Semiconductor datasheet embedded above: description, features and nomenclature from page 1, absolute maximums and recommended operating conditions from page 2, the Electrical Characteristics table from page 3, pin configuration and function description from page 4, application circuits from page 5, and package outlines from pages 7 to 8. Nothing from the Advanced Monolithic Systems datasheet is mixed in.</li>
<li><b>The 2 % accuracy call on the 1.2 V version</b> resolves a contradiction inside the datasheet itself, in favour of the Electrical Characteristics table over the Features bullet. See the note under the version table.</li>
<li><b>Symbol:</b> generated with <code>adom-symbol</code> to the datasheet's pin description table (1 = GND/ADJ, 2 = VOUT, 3 = VIN).</li>
<li><b>Footprints:</b> the KiCad 10 official library land patterns, renamed: <code>SOT-223-3_TabPin2</code>, <code>TO-252-3_TabPin2</code> and <code>SOT-89-3</code>. The <code>TabPin2</code> variants are correct here because the AMS1117 tab is V<sub>OUT</sub>, which is pin 2.</li>
<li><b>3D models:</b> the matching KiCad 10 official STEP models (<code>SOT-223.step</code>, <code>TO-252-3_TabPin2.step</code>, <code>SOT-89-3.step</code>), converted to GLB with <code>step2glb</code>.</li>
<li><b>Canonical JSON:</b> <code>ams1117.adom-lbr.json</code>, imported from the KiCad symbol + SOT-223 footprint with <code>adom-lbr import-kicad</code>.</li>
<li><b>Fusion and Altium libraries are deliberately absent.</b> They are generated rather than hand-verified, and the generated Altium symbol encoding has produced wrong geometry before, so nothing is shipped here until it can be checked in the tool itself.</li>
</ul>

</div>
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