hardware
[DEPRECATED] 1 A Low-Dropout Regulator - AMS1117 → ams-ams1117 / umw-ams1117
Public Made by Adomby adom
DEPRECATED - split by manufacturer. Use adom/ams-ams1117 (Advanced Monolithic Systems: 1.5-5.0 V incl. 2.85 V, SOT-223/TO-252/SO-8) or adom/umw-ams1117 (UMW/Youtai: 1.2-5.0 V, SOT-223/TO-252/SOT-89). The two vendors ship different voltage lineups, different packages and materially different limits.
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<div style="font-size:16px;font-weight:800;color:#d29922;letter-spacing:.04em;margin-bottom:8px">DEPRECATED: SPLIT BY MANUFACTURER</div>
<p style="margin:0 0 12px;font-size:14.5px;color:var(--text-body)">AMS1117 is second-sourced, and the two manufacturers ship <b>different voltage lineups, different packages and materially different limits</b>. Merging them onto one page meant every number needed a vendor caveat, which is exactly the sort of thing that gets misread off a datasheet page. This page has been split in two:</p>
<div style="display:grid;grid-template-columns:1fr 1fr;gap:12px">
<a href="https://wiki.adom.inc/adom/ams-ams1117" style="display:block;background:var(--surface);border:1px solid rgba(0,184,177,.34);border-radius:10px;padding:14px 16px;text-decoration:none">
<div style="font-size:12px;font-weight:800;letter-spacing:.1em;color:#00e6dc;text-transform:uppercase">The original</div>
<div style="font-size:15.5px;font-weight:700;color:var(--text);margin-top:6px">1 A Low-Dropout Regulator AMS - AMS1117</div>
<div style="font-size:13px;color:var(--text-2);margin-top:5px">Advanced Monolithic Systems · 1.5 to 5.0 V incl. <b>2.85 V</b> · SOT-223 / TO-252 / <b>SO-8</b></div></a>
<a href="https://wiki.adom.inc/adom/umw-ams1117" style="display:block;background:var(--surface);border:1px solid rgba(140,107,247,.34);border-radius:10px;padding:14px 16px;text-decoration:none">
<div style="font-size:12px;font-weight:800;letter-spacing:.1em;color:#a98bf9;text-transform:uppercase">Second source</div>
<div style="font-size:15.5px;font-weight:700;color:var(--text);margin-top:6px">1 A Low-Dropout Regulator UMW - AMS1117</div>
<div style="font-size:13px;color:var(--text-2);margin-top:5px">UMW / Youtai Semiconductor · <b>1.2 V</b> to 5.0 V · SOT-223 / TO-252 / <b>SOT-89</b></div></a>
</div>
<p style="margin:12px 0 0;font-size:13.5px;color:var(--text-2)"><b>Check your BOM before picking one.</b> If it does not name a manufacturer, design to the tighter of the two sets of limits. The content below is kept for reference and is no longer maintained.</p>
</div>
<div class=ident><h1>AMS1117</h1><span class=mfr>Advanced Monolithic Systems · UMW</span><span class=badge>1 A LDO</span></div>
<p class=oneline>Three-terminal <b>1 A low-dropout linear voltage regulator</b>, in seven fixed voltages across its two manufacturers (1.2 / 1.5 / 1.8 / 2.5 / 2.85 / 3.3 / 5.0 V) or an adjustable version set by two resistors around a 1.25 V reference. Operates down to <b>1 V input-to-output differential</b> (1.3 V max dropout at 0.8 A), with on-chip trimming to 1.5 %, internal current limit and thermal shutdown. Pin-compatible with older three-terminal SCSI regulators. Offered in SOT-223, TO-252 (DPAK) and 8-lead SOIC.</p>
<div class=metarow>
<span class=m>Output <b>1 A</b></span><span class=m>Dropout <b>1.3 V max</b></span><span class=m>V<sub>IN</sub> <b>15 / 18 V max</b></span>
<span class=m>Versions <b>7 fixed + ADJ</b></span><span class=m>Packages <b>SOT-223 · TO-252 · SO-8</b></span><span class=m>Pins <b>3 (8 on SO-8)</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 1.1 A typ · 900 mA min</div></div>
<div class=card><div class="k" style="color:#28c3d4">Dropout</div><div class=v>1.3 V max</div><div class=s>1.1 V typ at I<sub>OUT</sub> = 0.8 A</div></div>
<div class=card><div class="k" style="color:#4fb7f0">Fixed outputs</div><div class=v>7 versions</div><div class=s>1.2 · 1.5 · 1.8 · 2.5 · 2.85 · 3.3 · 5.0 V<br><span style="color:var(--text-3)">no single vendor sells all seven</span></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 · TO-252 (DPAK) · 8L SOIC</div></div>
<div class=card><div class="k" style="color:#a98bf9">Junction temp</div><div class=v>−40 to +125 °C</div><div class=s>Thermal shutdown at 165 °C</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>1.5 / 1.8 / 2.5 / 2.85 / 3.3 / 5.0 V (AMS) · 1.2 / 1.5 / 1.8 / 2.5 / 3.3 / 5.0 V (UMW). Also available adjustable</span></div>
<div class=spec><span class=lbl>Reference voltage</span><span>1.250 V typ (1.232 to 1.268 V at 25 °C, I<sub>OUT</sub> = 10 mA)</span></div>
<div class=spec><span class=lbl>Dropout voltage</span><span>1.1 V typ, 1.3 V max at I<sub>OUT</sub> = 0.8 A</span></div>
<div class=spec><span class=lbl>Input voltage</span><span>15 V absolute maximum (AMS) · 18 V absolute maximum, 12 V recommended (UMW)</span></div>
<div class=spec><span class=lbl>Line regulation</span><span>0.2 % max</span></div>
<div class=spec><span class=lbl>Load regulation</span><span>0.4 % max</span></div>
<div class=spec><span class=lbl>Current limit</span><span>900 mA min / 1100 typ / 1500 max at V<sub>IN</sub> − V<sub>OUT</sub> = 1.5 V (AMS) · 2.1 A min / 2.5 A max (UMW). A big difference, see below</span></div>
<div class=spec><span class=lbl>Quiescent current</span><span>5 mA typ, 11 mA max</span></div>
<div class=spec><span class=lbl>Minimum load current</span><span>5 mA typ, 10 mA max (adjustable version)</span></div>
<div class=spec><span class=lbl>Ripple rejection</span><span>60 dB min; 75 dB typ adjustable, 72 dB fixed, 68 dB on the 5.0 V version (120 Hz, C<sub>OUT</sub> = 22 µF)</span></div>
<div class=spec><span class=lbl>Adjust pin current</span><span>55 µA typ, 120 µA max</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>Long term stability</span><span>0.3 % typ, 1 % max (1000 h at 125 °C)</span></div>
<div class=spec><span class=lbl>Protection</span><span>Internal current limit + thermal shutdown: 165 °C (AMS) / 150 °C (UMW)</span></div>
<div class=spec><span class=lbl>Thermal resistance θ<sub>JA</sub></span><span>AMS: SOT-223 90 °C/W* · TO-252 80 · SO-8 160. UMW: SOT-223 88 · TO-252 86 · SOT-89 102. (*46 °C/W achievable with copper area)</span></div>
<div class=spec><span class=lbl>Operating junction temp</span><span>−40 to +125 °C · storage −65 to +150 °C</span></div>
<div class=spec><span class=lbl>Required output cap</span><span>22 µF solid tantalum. Part of the loop compensation, not optional</span></div>
</div>
<h2>Symbol & 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/ams1117/files/viewer-symbol.html"></iframe></div>
<div><div class=vh>PCB footprint: switch package bottom-right (SOT-223 / TO-252 / SO-8)</div>
<iframe class=vframe height=520 loading=lazy title="AMS1117 footprint (SOT-223 / TO-252 / SO-8)" src="https://wiki.adom.inc/api/v1/pages/adom/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 on SOT-223 / TO-252, 8 leads on SOIC</span></h2>
<div class=callout>On <b>both SOT-223 and TO-252 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. Both 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>SOT-223 & TO-252<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; feedback (adjust) 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>Unregulated input, 15 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>8-lead SOIC<span class=ct>8</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 node on the adjustable version</td></tr>
<tr><td class=pn>2</td><td class=nm>VOUT</td><td class=fx>Regulated output</td></tr>
<tr><td class=pn>3</td><td class=nm>VOUT</td><td class=fx>Regulated output. Tie all V<sub>OUT</sub> leads together</td></tr>
<tr><td class=pn>4</td><td class=nm>VIN</td><td class=fx>Unregulated input, 15 V max</td></tr>
<tr><td class=pn>5</td><td class=nm>N/C</td><td class=fx>No internal connection</td></tr>
<tr><td class=pn>6</td><td class=nm>VOUT</td><td class=fx>Regulated output</td></tr>
<tr><td class=pn>7</td><td class=nm>VOUT</td><td class=fx>Regulated output</td></tr>
<tr><td class=pn>8</td><td class=nm>N/C</td><td class=fx>No internal connection</td></tr>
</tbody></table></div>
</div>
<h2>Component variants</h2>
<div class=callout>All variants are the <b>same AMS1117 silicon</b>. The order code carries two independent choices: the <b>package</b> (a letter pair after the base part) and the <b>output voltage</b> (a suffix). A blank voltage suffix means the <b>adjustable</b> version.</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></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 / CS / blank</b></div><div class=ocdesc><code>CD</code> = TO-252 (DPAK) · <code>CS</code> = 8-lead SOIC · blank = SOT-223</div></div>
<div class=ocitem><div class=octop><span class=sw style="background:#00e6dc"></span><b style="color:#00e6dc">-3.3</b></div><div class=ocdesc>fixed output voltage. Blank = adjustable on AMS, spelled <code>-ADJ</code> by UMW</div></div>
</div>
</div>
<div class=vgrid>
<div class=vcard>
<h3>SOT-223<span class=chip style="background:rgba(139,148,158,.18);color:#8b949e">no letter</span><span class=mfb>AMS · UMW</span></h3>
<div class=sub>6.30 to 6.71 × 3.30 to 3.71 mm, 1.80 mm max height · 2.30 mm lead pitch · 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>-2.85</code> <code>-3.3</code> <code>-5.0</code><br><span style="color:var(--text-3)">-1.2 from UMW only, -2.85 from AMS only</span></div>
<div class=oc><b>Adjustable:</b> <code>AMS1117</code></div>
<div class=oc>θ<sub>JA</sub> <b>90 °C/W</b> · 1.2 W max dissipation</div>
</div>
<div class=vcard>
<h3>TO-252 (DPAK) <code style="font-size:13px">CD</code><span class=mfb>AMS · UMW</span></h3>
<div class=sub>6.48 to 6.73 × 5.97 to 6.22 mm body, 2.21 to 2.39 mm height · 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>-2.85</code> <code>-3.3</code> <code>-5.0</code><br><span style="color:var(--text-3)">-1.2 from UMW only, -2.85 from AMS only</span></div>
<div class=oc><b>Adjustable:</b> <code>AMS1117CD</code></div>
<div class=oc>θ<sub>JA</sub> <b>80 °C/W</b> · 2.2 W max dissipation. The best thermal option</div>
</div>
<div class=vcard>
<h3>8-lead SOIC <code style="font-size:13px">CS</code><span class=mf2>AMS only</span></h3>
<div class=sub>4.80 to 5.00 × 3.81 to 3.99 mm body, 1.27 mm pitch · V<sub>OUT</sub> on four leads</div>
<div class=oc><b>Fixed:</b> <code>AMS1117CS-1.5</code> <code>-1.8</code> <code>-2.5</code> <code>-2.85</code> <code>-3.3</code> <code>-5.0</code></div>
<div class=oc><b>Adjustable:</b> <code>AMS1117CS</code></div>
<div class=oc>θ<sub>JA</sub> <b>160 °C/W</b> · 780 mW max dissipation: lowest power</div>
</div>
</div>
<p style="color:var(--text-2);font-size:13.5px;margin:14px 0 0">UMW also offers a <b>SOT-89-3L</b> package (4.50 × 2.45 mm, θ<sub>JA</sub> 102 °C/W, order suffix <code>S</code>) that AMS does not. No CAD for it ships here yet.</p>
<h2>Output voltage versions</h2>
<p style="color:var(--text-2);font-size:14px;margin:0 0 10px">Seven fixed voltages exist across the two manufacturers, but <b>no single vendor sells all seven</b>: AMS carries 2.85 V and not 1.2 V, UMW carries 1.2 V and not 2.85 V. Limits below are from whichever datasheet defines that version; where both define it, the AMS figures are shown and UMW's differ slightly (see <a href="#twods">the two datasheets</a>).</p>
<table class=vt><thead><tr><th>Version</th><th>V<sub>OUT</sub> typ</th><th>Min to max at 25 °C</th><th>Accuracy</th><th>Ripple rej. typ</th><th>Available from</th></tr></thead><tbody>
<tr><td>AMS1117-1.2</td><td>1.200 V</td><td>1.176 to 1.224 V</td><td>2 %</td><td>75 dB</td><td><span class=mf1>UMW only</span></td></tr>
<tr><td>AMS1117-1.5</td><td>1.500 V</td><td>1.478 to 1.522 V</td><td>1.5 %</td><td>72 dB</td><td><span class=mfb>AMS · UMW</span></td></tr>
<tr><td>AMS1117-1.8</td><td>1.800 V</td><td>1.773 to 1.827 V</td><td>1.5 %</td><td>72 dB</td><td><span class=mfb>AMS · UMW</span></td></tr>
<tr><td>AMS1117-2.5</td><td>2.500 V</td><td>2.463 to 2.537 V</td><td>1.5 %</td><td>72 dB</td><td><span class=mfb>AMS · UMW</span></td></tr>
<tr><td>AMS1117-2.85</td><td>2.850 V</td><td>2.808 to 2.892 V</td><td>1.5 %</td><td>72 dB</td><td><span class=mf2>AMS only</span></td></tr>
<tr><td>AMS1117-3.3</td><td>3.300 V</td><td>3.251 to 3.349 V</td><td>1.5 %</td><td>72 dB</td><td><span class=mfb>AMS · UMW</span></td></tr>
<tr><td>AMS1117-5.0</td><td>5.000 V</td><td>4.925 to 5.075 V</td><td>1.5 %</td><td>68 dB</td><td><span class=mfb>AMS · UMW</span></td></tr>
<tr><td>AMS1117-ADJ</td><td>1.250 V ref</td><td>1.232 to 1.268 V</td><td>1.5 %</td><td>75 dB</td><td><span class=mfb>AMS · UMW</span></td></tr>
</tbody></table>
<p style="color:var(--text-3);font-size:13px;margin:10px 0 0">The adjustable version is ordered as plain <code>AMS1117</code> by AMS and as <code>AMS1117-ADJ</code> by UMW.</p>
<h2 id=twods>The two datasheets</h2>
<div class=callout><b>AMS1117 is not one company's part.</b> It began at <b>Advanced Monolithic Systems</b>, became a de-facto industry-standard pinout, and is now second-sourced by several vendors who each build their own die and publish their own datasheet. Both datasheets on this page are genuine and neither is a revision of the other. They describe <b>different silicon from different companies</b> that happen to share a part number, a pinout and a package set.</div>
<table class=vt><thead><tr><th> </th><th>Advanced Monolithic Systems <span style="font-weight:400;text-transform:none">(primary)</span></th><th>UMW / Youtai Semiconductor <span style="font-weight:400;text-transform:none">(alternate)</span></th></tr></thead><tbody>
<tr><td>Fixed voltages</td><td>1.5 · 1.8 · 2.5 · <b>2.85</b> · 3.3 · 5.0 V</td><td><b>1.2</b> · 1.5 · 1.8 · 2.5 · 3.3 · 5.0 V</td></tr>
<tr><td>Packages</td><td>SOT-223 · TO-252 · <b>SO-8</b></td><td>SOT-223-3L · TO-252-2L · <b>SOT-89-3L</b></td></tr>
<tr><td>V<sub>IN</sub> absolute max</td><td>15 V</td><td>18 V (12 V recommended)</td></tr>
<tr><td>Current limit</td><td>0.9 A min / 1.1 typ / 1.5 max</td><td><b>2.1 A min / 2.5 A max</b></td></tr>
<tr><td>Thermal shutdown</td><td>165 °C</td><td>150 °C</td></tr>
<tr><td>Dropout spec point</td><td>1.3 V max at <b>0.8 A</b></td><td>1.30 V max at <b>1.0 A</b> (1.20 V at 100 mA)</td></tr>
<tr><td>Line / load regulation</td><td>0.2 % / 0.4 % max</td><td>18 mV / 18 mV max</td></tr>
<tr><td>Quiescent current</td><td>5 mA typ, 11 max</td><td>5 mA typ, 10 max</td></tr>
<tr><td>Adjust pin current</td><td>55 µA typ, 120 max</td><td>60 µA typ, 120 max</td></tr>
<tr><td>θ<sub>JA</sub></td><td>SOT-223 90 · TO-252 80 · SO-8 160 °C/W</td><td>SOT-223 88 · TO-252 86 · SOT-89 102 °C/W</td></tr>
<tr><td>ESD rating</td><td>not specified</td><td>2000 V min</td></tr>
</tbody></table>
<h3 style="font-size:16px;margin:26px 0 10px;color:var(--text)">Why they differ</h3>
<ul class=ul>
<li><b>Different companies, different silicon.</b> AMS1117 is Advanced Monolithic Systems' original part number, not a JEDEC standard. UMW (Youtai Semiconductor) builds its own die to the same three-terminal pinout and publishes its own tested limits. The gaps are real device differences, not documentation errors, and they are why a board qualified on one vendor's part is not automatically qualified on the other's.</li>
<li><b>The voltage lineups follow each vendor's market.</b> <b>2.85 V is the SCSI-2 active-termination voltage</b>. The AMS datasheet lists "Active SCSI Terminators" as an application, and 2.85 V regulators exist almost entirely to hold a SCSI bus at spec through 110 Ω series resistors. UMW's applications are laptops, cellular phones and SMPS post-regulation, so it drops 2.85 V and carries <b>1.2 V</b> instead, which is the modern SoC / FPGA / gigabit-PHY core rail. Neither vendor is missing a part; they are serving different demand.</li>
<li><b>Some differences are units and test conditions, not silicon.</b> AMS quotes line and load regulation as a percentage and specifies dropout at 0.8 A; UMW quotes millivolts and specifies dropout at 100 mA, 500 mA and 1 A. Comparing those numbers directly is misleading. The current limit and thermal-shutdown differences, by contrast, are genuine.</li>
<li><b>The 1.2 V part is the loosest of the family.</b> UMW rates it to <b>2 %</b> where every other version is 1.5 %, because 1.2 V sits closest to the 1.25 V bandgap reference and leaves the least headroom for trimming.</li>
<li><b>Practical consequence:</b> if a design needs 2.85 V you must buy AMS or another vendor that carries it; if it needs 1.2 V you must buy UMW or another second source. For the five shared voltages, either works, but design to the <b>tighter</b> of the two sets of limits if the BOM does not pin a manufacturer.</li>
</ul>
<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 symbols</td><td><a href=ams1117.kicad_sym>ams1117.kicad_sym</a> (3-pin) · <a href=ams1117-so8.kicad_sym>ams1117-so8.kicad_sym</a> (8-lead)</td></tr>
<tr><td class=tool style="color:#28c3d4">KiCad footprints</td><td><a href=ams1117-sot223.kicad_mod>AMS1117_SOT-223</a> · <a href=ams1117-to252.kicad_mod>AMS1117_TO-252</a> · <a href=ams1117-so8.kicad_mod>AMS1117_SO-8</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> · TO-252 <a href=ams1117-to252.step>.step</a> / <a href=ams1117-to252.glb>.glb</a> · SO-8 <a href=ams1117-so8.step>.step</a> / <a href=ams1117-so8.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/ams1117-3v3-molecule"><b>AMS1117-3.3 Molecule</b></a>. A 5 V → 3.3 V regulator brick: AMS1117-3.3 in SOT-223 with 10 µF input and 22 µF output decoupling on a machine-pin carrier.</li>
<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.</li>
</ul>
<p style="color:var(--text-2);font-size:13.5px;margin:12px 0 0">Per-voltage pages: <a href="https://wiki.adom.inc/adom/ams1117-3-3">adom/ams1117-3-3</a> · <a href="https://wiki.adom.inc/adom/ams1117-1-2">adom/ams1117-1-2</a> (the 1.2 V version. A UMW part, documented by the alternate datasheet below).</p>
<h2>Application notes</h2>
<ul class=ul>
<li><b>The 22 µF output capacitor is compensation, not decoupling.</b> The AMS1117 loop depends on it; a solid tantalum 22 µF guarantees stability across all operating conditions. Bypassing the adjust pin raises the requirement further.</li>
<li><b>No protection diodes needed.</b> Unlike older regulators, internal resistors limit the adjust-pin current paths, so no diode from ADJ to output or input is required. A diode from output to input is only recommended when C<sub>OUT</sub> is large (1000 to 5000 µF) and the input can be shorted.</li>
<li><b>Kelvin the divider, not the load.</b> On the adjustable version, connect the top of R1 to the regulator case rather than the load, so parasitic line resistance is not multiplied by the divider ratio. Fixed versions Kelvin the top of R1 internally, so the ground pin can do negative-side sensing.</li>
<li><b>Copper is the heat sink.</b> θ<sub>JA</sub> falls from 90 to about 55 °C/W with 2500 mm² of copper on both sides. The spreading copper does not have to be electrically connected to the tab to work.</li>
<li><b>Adjustable output:</b> V<sub>OUT</sub> = V<sub>REF</sub>(1 + R2/R1) + I<sub>ADJ</sub>R2, with V<sub>REF</sub> = 1.25 V and I<sub>ADJ</sub> ≈ 55 µA. The I<sub>ADJ</sub> term is small and constant and can usually be ignored.</li>
</ul>
<h2>Datasheets</h2>
<div class=vh style="font-size:14px;margin-bottom:9px"><b style="color:var(--text)">Primary</b>: Advanced Monolithic Systems, <i>AMS1117 1 A Low Dropout Voltage Regulator</i>. Every unattributed number on this page comes from here.</div>
<iframe class=dsheet loading=lazy title="AMS1117 datasheet (Advanced Monolithic Systems)" src="https://wiki.adom.inc/api/v1/pages/adom/ams1117/files/docs/ams1117-datasheet.pdf"></iframe>
<p style="margin:8px 0 26px;font-size:13px"><a href=docs/ams1117-datasheet.pdf>Download (PDF)</a> · <a href="http://www.advanced-monolithic.com/pdf/ds1117.pdf">advanced-monolithic.com</a></p>
<div class=vh style="font-size:14px;margin-bottom:9px"><b style="color:var(--text)">Alternate</b>: UMW (Youtai Semiconductor), <i>AMS1117 1 A LDO Voltage Regulator</i>. The second source: <b>the only one of the two that documents the 1.2 V version</b>, and the one to use if your BOM specifies a UMW part.</div>
<iframe class=dsheet loading=lazy title="AMS1117 datasheet (UMW / Youtai Semiconductor)" src="https://wiki.adom.inc/api/v1/pages/adom/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 (PDF)</a> · <a href="https://www.umw-ic.com">umw-ic.com</a></p>
<h2>Provenance</h2>
<ul class=ul>
<li><b>Unattributed electrical numbers</b> are read from the Advanced Monolithic Systems datasheet embedded above. Features and ordering from page 1, limits from the Electrical Characteristics tables on pages 2 to 3, application guidance from pages 4 to 5, package dimensions from pages 7 to 8.</li>
<li><b>Anything marked UMW</b>. The 1.2 V version, the SOT-89 package, the 18 V input rating, the 2.1 to 2.5 A current limit and the 150 °C thermal shutdown: is read from the UMW / Youtai Semiconductor datasheet, also embedded above.</li>
<li><b>The 2.85 V / SCSI claim</b> is from the AMS datasheet's own applications list plus the SCSI-2 active-termination literature (Linear Technology Design Note 34, which uses an LT1117-2.85 for exactly this).</li>
<li><b>Symbols:</b> generated with <code>adom-symbol</code> to the datasheet pin connections (3-pin fixed/adjustable version, and the 8-lead SOIC pinout).</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>SOIC-8_3.9x4.9mm_P1.27mm</code>. The <code>TabPin2</code> variants are the correct choice 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>SOIC-8_3.9x4.9mm_P1.27mm.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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