hardware
1 A Low-Dropout Regulator AMS - AMS1117
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Advanced Monolithic Systems AMS1117 - the original three-terminal 1 A low-dropout linear regulator. Fixed 1.5/1.8/2.5/2.85/3.3/5.0 V or adjustable, in SOT-223, TO-252 (DPAK) and 8-lead SOIC.
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 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 to 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 to 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 |
| n/a | 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 to 6.71 × 3.30 to 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 to 6.73 × 5.97 to 6.22 mm, 2.21 to 2.39 mm | 80 °C/W | 2.2 W | AMS1117CD-1.5 … AMS1117CD-5.0 |
| 8-lead SOIC | CS |
4.80 to 5.00 × 3.81 to 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 to max | Test VIN | Line reg. typ / max | Load reg. typ / max | Ripple rej. typ |
|---|---|---|---|---|---|---|
| AMS1117-1.5 | 1.500 V | 1.478 to 1.522 V | 3.0 V | 0.3 / 5 mV | 3 / 10 mV | 72 dB |
| AMS1117-1.8 | 1.800 V | 1.773 to 1.827 V | 3.3 V | 0.3 / 5 mV | 3 / 10 mV | 72 dB |
| AMS1117-2.5 | 2.500 V | 2.463 to 2.537 V | 4.0 V | 0.3 / 6 mV | 3 / 12 mV | 72 dB |
| AMS1117-2.85 | 2.850 V | 2.808 to 2.892 V | 4.35 V | 0.3 / 6 mV | 3 / 12 mV | 72 dB |
| AMS1117-3.3 | 3.300 V | 3.251 to 3.349 V | 4.8 V | 0.5 / 10 mV | 3 / 15 mV | 72 dB |
| AMS1117-5.0 | 5.000 V | 4.925 to 5.075 V | 6.5 V | 0.5 / 10 mV | 5 / 20 mV | 68 dB |
| AMS1117 (ADJ) | 1.250 V ref | 1.232 to 1.268 V | n/a | 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 (3-pin), ams1117-so8.kicad_sym (8-lead) |
| KiCad footprints | ams1117-sot223.kicad_mod, ams1117-to252.kicad_mod, ams1117-so8.kicad_mod |
| 3D models | ams1117-sot223.step / .glb, ams1117-to252.step / .glb, ams1117-so8.step / .glb |
| Canonical | ams1117.adom-lbr.json |
| Fusion 360 / EAGLE | Not available yet |
| Altium | Not available yet |
Applications
- AMS1117-3.3 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.
- 1 A Low-Dropout Regulator 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 large (1000 to 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 to 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. Every electrical number on this page is read from it. Nothing from any second source is mixed in.
- Symbols: generated with
adom-symbolto 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. TheTabPin2variants 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.
# 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 to 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 to 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 |
| n/a | 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 to 6.71 × 3.30 to 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 to 6.73 × 5.97 to 6.22 mm, 2.21 to 2.39 mm | 80 °C/W | 2.2 W | `AMS1117CD-1.5` … `AMS1117CD-5.0` |
| 8-lead SOIC | `CS` | 4.80 to 5.00 × 3.81 to 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 to max | Test VIN | Line reg. typ / max | Load reg. typ / max | Ripple rej. typ |
|---|---|---|---|---|---|---|
| AMS1117-1.5 | 1.500 V | 1.478 to 1.522 V | 3.0 V | 0.3 / 5 mV | 3 / 10 mV | 72 dB |
| AMS1117-1.8 | 1.800 V | 1.773 to 1.827 V | 3.3 V | 0.3 / 5 mV | 3 / 10 mV | 72 dB |
| AMS1117-2.5 | 2.500 V | 2.463 to 2.537 V | 4.0 V | 0.3 / 6 mV | 3 / 12 mV | 72 dB |
| AMS1117-2.85 | 2.850 V | 2.808 to 2.892 V | 4.35 V | 0.3 / 6 mV | 3 / 12 mV | 72 dB |
| AMS1117-3.3 | 3.300 V | 3.251 to 3.349 V | 4.8 V | 0.5 / 10 mV | 3 / 15 mV | 72 dB |
| AMS1117-5.0 | 5.000 V | 4.925 to 5.075 V | 6.5 V | 0.5 / 10 mV | 5 / 20 mV | 68 dB |
| AMS1117 (ADJ) | 1.250 V ref | 1.232 to 1.268 V | n/a | 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 large (1000 to 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 to 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.