1 A Low-Dropout Regulator AMS - AMS1117

@@ -0,0 +1,132 @@+# AMS1117 — 1 A Low-Dropout Regulator (Advanced Monolithic Systems)++The **original** AMS1117: a three-terminal **1 A low-dropout linear voltage regulator** from Advanced Monolithic Systems, available in fixed 1.5 / 1.8 / 2.5 / 2.85 / 3.3 / 5.0 V versions or as an adjustable regulator set by two resistors around a 1.25 V reference. It operates down to 1 V input-to-output differential (1.3 V max dropout at 0.8 A), is trimmed on-chip to 1.5 %, and includes internal current limiting and thermal shutdown. It is pin-compatible with older three-terminal SCSI regulators, and comes in SOT-223, TO-252 (DPAK) and 8-lead SOIC.++> **This page is the Advanced Monolithic Systems part only.** Everything here comes from the AMS datasheet and applies to AMS-branded silicon. The same part number is second-sourced by UMW with a different voltage lineup, different packages and materially different limits — if your BOM says UMW, use [1 A Low-Dropout Regulator UMW — AMS1117](https://wiki.adom.inc/adom/umw-ams1117) instead.++The interactive **symbol** and **footprint** viewers above are rendered by the wiki from the CAD shipped with this page. Use the toggle at the **bottom-right of the footprint viewer** to switch between **SOT-223**, **TO-252** and **SO-8**.++## Specifications++- **Output current** — 1 A+- **Fixed output voltages** — 1.5 / 1.8 / 2.5 / 2.85 / 3.3 / 5.0 V; also available adjustable+- **Reference voltage** — 1.250 V typ (1.232 – 1.268 V at 25 °C)+- **Dropout voltage** — 1.1 V typ, 1.3 V max at 0.8 A; higher above 0.8 A+- **Input voltage** — 15 V absolute maximum+- **Line regulation** — 0.2 % max (0.015 % typ)+- **Load regulation** — 0.4 % max (0.1 % typ)+- **Current limit** — 900 mA min / 1100 mA typ / 1500 mA max+- **Quiescent current** — 5 mA typ, 11 mA max+- **Minimum load current** — 5 mA typ, 10 mA max (adjustable version)+- **Ripple rejection** — 60 dB min; 75 dB typ adjustable, 72 dB fixed, 68 dB on the 5.0 V version+- **Adjust pin current** — 55 µA typ, 120 µA max+- **Thermal regulation** — 0.008 %/W typ, 0.04 %/W max+- **RMS output noise** — 0.003 % of VOUT (10 Hz – 10 kHz)+- **Long term stability** — 0.3 % typ, 1 % max (1000 h at 125 °C)+- **Protection** — internal current limit and thermal shutdown at 165 °C junction+- **Thermal resistance θJA** — SOT-223 90 °C/W, TO-252 80 °C/W, SO-8 160 °C/W (θJC 15 °C/W max)+- **Operating junction temperature** — −40 to +125 °C; storage −65 to +150 °C+- **Required output capacitor** — 22 µF solid tantalum (part of the loop compensation)++## Pin configuration++On **both SOT-223 and TO-252 the metal tab is VOUT**, internally bonded to pin 2. It is the heat path, so solder it to a copper pour on the output net — never to ground. Both footprints shipped here carry the tab as pad 2.++### SOT-223 and TO-252 — 3 terminals plus tab++| Pin | Name | Function |+|---|---|---|+| 1 | GND/ADJ | Ground on fixed versions; feedback (adjust) node on the adjustable version |+| 2 | VOUT | Regulated output — also the metal tab |+| 3 | VIN | Unregulated input, 15 V max |+| — | TAB | Thermal pad, bonded to pin 2 (VOUT) |++### 8-lead SOIC++| Pin | Name | Function |+|---|---|---|+| 1 | GND/ADJ | Ground on fixed versions; adjust node on the adjustable version |+| 2 | VOUT | Regulated output |+| 3 | VOUT | Regulated output — tie all VOUT leads together |+| 4 | VIN | Unregulated input, 15 V max |+| 5 | N/C | No internal connection |+| 6 | VOUT | Regulated output |+| 7 | VOUT | Regulated output |+| 8 | N/C | No internal connection |++## Component variants++All variants are the **same AMS1117 silicon**. The order code carries two independent choices: the **package** (a letter pair after the base part) and the **output voltage** (a suffix). A blank voltage suffix means the **adjustable** version. Every version is available in all three packages.++The order code is `AMS1117` `{CD | CS | blank}` `-{voltage}` — where `CD` = TO-252 (DPAK), `CS` = 8-lead SOIC, blank = SOT-223.++| Package | Code | Body | θJA | Max dissipation | Fixed order codes |+|---|---|---|---|---|---|+| SOT-223 | *(none)* | 6.30–6.71 × 3.30–3.71 mm, 1.80 mm max | 90 °C/W | 1.2 W | `AMS1117-1.5` … `AMS1117-5.0` |+| TO-252 (DPAK) | `CD` | 6.48–6.73 × 5.97–6.22 mm, 2.21–2.39 mm | 80 °C/W | 2.2 W | `AMS1117CD-1.5` … `AMS1117CD-5.0` |+| 8-lead SOIC | `CS` | 4.80–5.00 × 3.81–3.99 mm, 1.27 mm pitch | 160 °C/W | 780 mW | `AMS1117CS-1.5` … `AMS1117CS-5.0` |++### Output voltage versions++Limits at TJ = 25 °C. Load regulation is measured at 0 ≤ IOUT ≤ 0.8 A.++| Version | VOUT typ | Min – max | Test VIN | Line reg. typ / max | Load reg. typ / max | Ripple rej. typ |+|---|---|---|---|---|---|---|+| AMS1117-1.5 | 1.500 V | 1.478 – 1.522 V | 3.0 V | 0.3 / 5 mV | 3 / 10 mV | 72 dB |+| AMS1117-1.8 | 1.800 V | 1.773 – 1.827 V | 3.3 V | 0.3 / 5 mV | 3 / 10 mV | 72 dB |+| AMS1117-2.5 | 2.500 V | 2.463 – 2.537 V | 4.0 V | 0.3 / 6 mV | 3 / 12 mV | 72 dB |+| AMS1117-2.85 | 2.850 V | 2.808 – 2.892 V | 4.35 V | 0.3 / 6 mV | 3 / 12 mV | 72 dB |+| AMS1117-3.3 | 3.300 V | 3.251 – 3.349 V | 4.8 V | 0.5 / 10 mV | 3 / 15 mV | 72 dB |+| AMS1117-5.0 | 5.000 V | 4.925 – 5.075 V | 6.5 V | 0.5 / 10 mV | 5 / 20 mV | 68 dB |+| AMS1117 (ADJ) | 1.250 V ref | 1.232 – 1.268 V | — | 0.015 / 0.2 % | 0.1 / 0.3 % | 75 dB |++**2.85 V is here for SCSI.** It is the SCSI-2 active-termination voltage — the 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. It is the one version the UMW second source does not carry.++## Thermal design++PD = (VIN − VOUT) × IOUT, and TJ = TA(max) + PD·θJA must stay under 125 °C. The datasheet's measured SOT-223 θJA against copper area, on 1/16" FR-4 with 1 oz foil:++| Top-side copper | Back-side copper | Board area | θJA |+|---|---|---|---|+| 2500 mm² | 2500 mm² | 2500 mm² | 55 °C/W |+| 1000 mm² | 2500 mm² | 2500 mm² | 55 °C/W |+| 225 mm² | 2500 mm² | 2500 mm² | 65 °C/W |+| 100 mm² | 2500 mm² | 2500 mm² | 80 °C/W |+| 1000 mm² | 1000 mm² | 1000 mm² | 60 °C/W |+| 1000 mm² | 0 | 1000 mm² | 65 °C/W |++The tab is attached to the top-side copper in every row. The spreading copper does **not** have to be electrically connected to the tab to be effective.++## Assets++| Tool | Files |+|---|---|+| **KiCad symbols** | [`ams1117.kicad_sym`](ams1117.kicad_sym) (3-pin), [`ams1117-so8.kicad_sym`](ams1117-so8.kicad_sym) (8-lead) |+| **KiCad footprints** | [`ams1117-sot223.kicad_mod`](ams1117-sot223.kicad_mod), [`ams1117-to252.kicad_mod`](ams1117-to252.kicad_mod), [`ams1117-so8.kicad_mod`](ams1117-so8.kicad_mod) |+| **3D models** | [`ams1117-sot223.step`](ams1117-sot223.step) / [`.glb`](ams1117-sot223.glb), [`ams1117-to252.step`](ams1117-to252.step) / [`.glb`](ams1117-to252.glb), [`ams1117-so8.step`](ams1117-so8.step) / [`.glb`](ams1117-so8.glb) |+| **Canonical** | [`ams1117.adom-lbr.json`](ams1117.adom-lbr.json) |+| **Fusion 360 / EAGLE** | *Not available yet* |+| **Altium** | *Not available yet* |++## Applications++1. [**AMS1117-3.3 Molecule**](https://wiki.adom.inc/adom/ams1117-3v3-molecule) — 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.+2. [**1 A Low-Dropout Regulator UMW — AMS1117**](https://wiki.adom.inc/adom/umw-ams1117) — the second-source part.++## Application notes++- **The 22 µF output capacitor is compensation, not decoupling.** The AMS1117 loop depends on it; a solid tantalum 22 µF guarantees stability across all operating conditions.+- **No protection diodes needed.** Internal resistors limit the adjust-pin current paths. A diode from output to input is only recommended when COUT is very large (1000–5000 µF) and the input can be shorted.+- **Kelvin the divider, not the load.** On the adjustable version, connect the top of R1 to the regulator case rather than the load. Fixed versions Kelvin the top of R1 internally.+- **Adjust-pin bypassing.** For proper ripple rejection the adjust-pin capacitor's impedance at the ripple frequency must be below R1 (typically 100–200 Ω): >13 µF at 120 Hz with R1 = 100 Ω, but only 0.16 µF at 10 kHz.+- **Adjustable output:** VOUT = VREF(1 + R2/R1) + IADJ·R2, with VREF = 1.25 V and IADJ ≈ 55 µA.++## Provenance++- **Datasheet:** [Advanced Monolithic Systems AMS1117, *1 A Low Dropout Voltage Regulator*](docs/ams1117-datasheet-ams.pdf) — every electrical number on this page is read from it. Nothing from any second source is mixed in.+- **Symbols:** generated with `adom-symbol` to the datasheet pin connections.+- **Footprints:** KiCad 10 official library land patterns, renamed — `SOT-223-3_TabPin2`, `TO-252-3_TabPin2`, `SOIC-8_3.9x4.9mm_P1.27mm`. The `TabPin2` variants are correct here because the AMS1117 tab is VOUT, which is pin 2.+- **3D models:** the matching KiCad 10 official STEP models, converted to GLB with `step2glb`.+- **Canonical JSON:** imported from the KiCad symbol + SOT-223 footprint with `adom-lbr import-kicad`.+- **The SCSI note** draws on the 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).+- **Fusion and Altium libraries are deliberately absent** — they are generated rather than hand-verified, and the generated Altium symbol encoding has produced wrong geometry before.