DEPRECATED: SPLIT BY MANUFACTURER

AMS1117 is second-sourced, and the two manufacturers ship different voltage lineups, different packages and materially different limits. 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:

The original
1 A Low-Dropout Regulator AMS - AMS1117
Advanced Monolithic Systems · 1.5 to 5.0 V incl. 2.85 V · SOT-223 / TO-252 / SO-8
Second source
1 A Low-Dropout Regulator UMW - AMS1117
UMW / Youtai Semiconductor · 1.2 V to 5.0 V · SOT-223 / TO-252 / SOT-89

Check your BOM before picking one. 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 The content below is kept for reference and is no longer maintained.

# AMS1117

Advanced Monolithic Systems · UMW 1 A LDO

Three-terminal 1 A low-dropout linear voltage regulator, 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 1 V input-to-output differential (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.

Output 1 A Dropout 1.3 V max VIN 15 / 18 V max Versions 7 fixed + ADJ Packages SOT-223 · TO-252 · SO-8 Pins 3 (8 on SO-8)

## At a glance

Output current
1 A
Current limit 1.1 A typ · 900 mA min
Dropout
1.3 V max
1.1 V typ at IOUT = 0.8 A
Fixed outputs
7 versions
1.2 · 1.5 · 1.8 · 2.5 · 2.85 · 3.3 · 5.0 V
no single vendor sells all seven
Adjustable
1.25 V ref
VOUT = VREF(1 + R2/R1) + IADJR2
Packages
3 options
SOT-223 · TO-252 (DPAK) · 8L SOIC
Junction temp
−40 to +125 °C
Thermal shutdown at 165 °C

## Specifications

Output current 1 A
Fixed output voltages 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
Reference voltage 1.250 V typ (1.232 to 1.268 V at 25 °C, IOUT = 10 mA)
Dropout voltage 1.1 V typ, 1.3 V max at IOUT = 0.8 A
Input voltage 15 V absolute maximum (AMS) · 18 V absolute maximum, 12 V recommended (UMW)
Line regulation 0.2 % max
Load regulation 0.4 % max
Current limit 900 mA min / 1100 typ / 1500 max at VIN − VOUT = 1.5 V (AMS) · 2.1 A min / 2.5 A max (UMW). A big difference, see below
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 (120 Hz, COUT = 22 µF)
Adjust pin current 55 µA typ, 120 µA 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 + thermal shutdown: 165 °C (AMS) / 150 °C (UMW)
Thermal resistance θJA 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)
Operating junction temp−40 to +125 °C · storage −65 to +150 °C
Required output cap 22 µF solid tantalum. Part of the loop compensation, not optional

## Symbol & footprint

Schematic symbol: hover a pin for its function
PCB footprint: switch package bottom-right (SOT-223 / TO-252 / SO-8)

## Pin map 3 terminals on SOT-223 / TO-252, 8 leads on SOIC

On both SOT-223 and TO-252 the metal tab is VOUT, 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.
SOT-223 & TO-2523 + tab

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 SOIC8

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.
AMS1117 CD-3.3
AMS1117
base part: 1 A LDO
CD / CS / blank
`CD` = TO-252 (DPAK) · `CS` = 8-lead SOIC · blank = SOT-223
-3.3
fixed output voltage. Blank = adjustable on AMS, spelled `-ADJ` by UMW

### SOT-223no letter AMS · UMW

6.30 to 6.71 × 3.30 to 3.71 mm, 1.80 mm max height · 2.30 mm lead pitch · tab = VOUT
Fixed: `AMS1117-1.2` `-1.5` `-1.8` `-2.5` `-2.85` `-3.3` `-5.0`
-1.2 from UMW only, -2.85 from AMS only
Adjustable: `AMS1117`
θJA 90 °C/W · 1.2 W max dissipation

### TO-252 (DPAK) `CD` AMS · UMW

6.48 to 6.73 × 5.97 to 6.22 mm body, 2.21 to 2.39 mm height · tab = VOUT
Fixed: `AMS1117CD-1.2` `-1.5` `-1.8` `-2.5` `-2.85` `-3.3` `-5.0`
-1.2 from UMW only, -2.85 from AMS only
Adjustable: `AMS1117CD`
θJA 80 °C/W · 2.2 W max dissipation. The best thermal option

### 8-lead SOIC `CS` AMS only

4.80 to 5.00 × 3.81 to 3.99 mm body, 1.27 mm pitch · VOUT on four leads
Fixed: `AMS1117CS-1.5` `-1.8` `-2.5` `-2.85` `-3.3` `-5.0`
Adjustable: `AMS1117CS`
θJA 160 °C/W · 780 mW max dissipation: lowest power

UMW also offers a SOT-89-3L package (4.50 × 2.45 mm, θJA 102 °C/W, order suffix `S`) that AMS does not. No CAD for it ships here yet.

## Output voltage versions

Seven fixed voltages exist across the two manufacturers, but no single vendor sells all seven: 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 the two datasheets).

Version | VOUT typ | Min to max at 25 °C | Accuracy | Ripple rej. typ | Available from
--- | --- | --- | --- | --- | ---
AMS1117-1.2 | 1.200 V | 1.176 to 1.224 V | 2 % | 75 dB | UMW only
AMS1117-1.5 | 1.500 V | 1.478 to 1.522 V | 1.5 % | 72 dB | AMS · UMW
AMS1117-1.8 | 1.800 V | 1.773 to 1.827 V | 1.5 % | 72 dB | AMS · UMW
AMS1117-2.5 | 2.500 V | 2.463 to 2.537 V | 1.5 % | 72 dB | AMS · UMW
AMS1117-2.85 | 2.850 V | 2.808 to 2.892 V | 1.5 % | 72 dB | AMS only
AMS1117-3.3 | 3.300 V | 3.251 to 3.349 V | 1.5 % | 72 dB | AMS · UMW
AMS1117-5.0 | 5.000 V | 4.925 to 5.075 V | 1.5 % | 68 dB | AMS · UMW
AMS1117-ADJ | 1.250 V ref | 1.232 to 1.268 V | 1.5 % | 75 dB | AMS · UMW

The adjustable version is ordered as plain `AMS1117` by AMS and as `AMS1117-ADJ` by UMW.

## The two datasheets

AMS1117 is not one company's part. It began at Advanced Monolithic Systems, 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 different silicon from different companies that happen to share a part number, a pinout and a package set.

| Advanced Monolithic Systems (primary) | UMW / Youtai Semiconductor (alternate)
--- | --- | ---
Fixed voltages | 1.5 · 1.8 · 2.5 · 2.85 · 3.3 · 5.0 V | 1.2 · 1.5 · 1.8 · 2.5 · 3.3 · 5.0 V
Packages | SOT-223 · TO-252 · SO-8 | SOT-223-3L · TO-252-2L · SOT-89-3L
VIN absolute max | 15 V | 18 V (12 V recommended)
Current limit | 0.9 A min / 1.1 typ / 1.5 max | 2.1 A min / 2.5 A max
Thermal shutdown | 165 °C | 150 °C
Dropout spec point | 1.3 V max at 0.8 A | 1.30 V max at 1.0 A (1.20 V at 100 mA)
Line / load regulation | 0.2 % / 0.4 % max | 18 mV / 18 mV max
Quiescent current | 5 mA typ, 11 max | 5 mA typ, 10 max
Adjust pin current | 55 µA typ, 120 max | 60 µA typ, 120 max
θJA | SOT-223 90 · TO-252 80 · SO-8 160 °C/W | SOT-223 88 · TO-252 86 · SOT-89 102 °C/W
ESD rating | not specified | 2000 V min

### Why they differ

- Different companies, different silicon. 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.
- The voltage lineups follow each vendor's market. 2.85 V is the SCSI-2 active-termination voltage. 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 1.2 V instead, which is the modern SoC / FPGA / gigabit-PHY core rail. Neither vendor is missing a part; they are serving different demand.
- Some differences are units and test conditions, not silicon. 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.
- The 1.2 V part is the loosest of the family. UMW rates it to 2 % 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.
- Practical consequence: 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 tighter of the two sets of limits if the BOM does not pin a manufacturer.

## Assets

KiCad symbol, all three footprints and matching 3D models, plus the canonical adom-lbr JSON the rest is generated from.

KiCad symbols | ams1117.kicad_sym (3-pin) · ams1117-so8.kicad_sym (8-lead)
KiCad footprints | AMS1117_SOT-223 · AMS1117_TO-252 · AMS1117_SO-8
3D models | SOT-223 .step / .glb · TO-252 .step / .glb · SO-8 .step / .glb
Canonical | ams1117.adom-lbr.json
Fusion 360 / EAGLE | Not available yet
Altium | Not available yet

## Implementation

- 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.
- Large Automotive Eth Switch Molecule. An AMS1117-1.2 supplies the KSZ9131 gigabit PHY 1.2 V core rail (U902) from the board's 3.3 V rail.

Per-voltage pages: adom/ams1117-3-3 · adom/ams1117-1-2 (the 1.2 V version. A UMW part, documented by the alternate datasheet below).

## 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. Bypassing the adjust pin raises the requirement further.
- No protection diodes needed. 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 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, 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.
- Copper is the heat sink. θJA 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.
- Adjustable output: VOUT = VREF(1 + R2/R1) + IADJR2, with VREF = 1.25 V and IADJ ≈ 55 µA. The IADJ term is small and constant and can usually be ignored.

## Datasheets

Primary: Advanced Monolithic Systems, AMS1117 1 A Low Dropout Voltage Regulator. Every unattributed number on this page comes from here.

Download (PDF) · advanced-monolithic.com

Alternate: UMW (Youtai Semiconductor), AMS1117 1 A LDO Voltage Regulator. The second source: the only one of the two that documents the 1.2 V version, and the one to use if your BOM specifies a UMW part.

Download (PDF) · umw-ic.com

## Provenance

- Unattributed electrical numbers 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.
- Anything marked UMW. 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.
- The 2.85 V / SCSI claim 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).
- Symbols: generated with `adom-symbol` to the datasheet pin connections (3-pin fixed/adjustable version, and the 8-lead SOIC pinout).
- Footprints: the KiCad 10 official library land patterns, renamed: `SOT-223-3_TabPin2`, `TO-252-3_TabPin2` and `SOIC-8_3.9x4.9mm_P1.27mm`. The `TabPin2` variants are the correct choice here because the AMS1117 tab is VOUT, which is pin 2.
- 3D models: the matching KiCad 10 official STEP models (`SOT-223.step`, `TO-252-3_TabPin2.step`, `SOIC-8_3.9x4.9mm_P1.27mm.step`), converted to GLB with `step2glb`.
- Canonical JSON: `ams1117.adom-lbr.json`, imported from the KiCad symbol + SOT-223 footprint with `adom-lbr import-kicad`.
- 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, so nothing is shipped here until it can be checked in the tool itself.