AMS1117 3.3V Pinout, Datasheet Specs & Input Voltage
Everything you need to wire an AMS1117 correctly: the pinout, the numbers that matter from the datasheet, the capacitors it needs, and why it gets hot, resets your board or drains your battery.
Quick answer: AMS1117-3.3
- Pinout (SOT-223, top view): pin 1 = GND (ADJ on the adjustable version), pin 2 = VOUT, pin 3 = VIN. The tab is VOUT.
- Input voltage: needs about 4.6 V minimum for a steady 3.3 V (1.3 V dropout). Line regulation is specified up to 12 V, but heat limits you long before that.
- Current: up to 1 A, but from 5 V every 100 mA wastes 0.17 W as heat.
- Capacitors: 10 µF tantalum on input and output (output ESR ≤ 0.5 Ω).
- Idle current: 3 mA typ (10 mA max), too high for battery projects.
- Better for low-current rails: a CMOS LDO like the TI TLV740P (50 µA idle, 460 mV dropout). See our AMS1117 vs TLV740P comparison →
AMS1117 pinout
| Pin | Name | Connect to |
|---|---|---|
| 1 | GND (ADJ) | Ground. On the ADJ version: resistor divider to set the output |
| 2 | VOUT | 3.3 V load + output capacitor |
| 3 | VIN | Input supply (≥ 4.6 V) + input capacitor |
| Tab | VOUT | Same as pin 2; solder to copper for cooling |
On a module, the header is usually labelled VIN GND VOUT (or 5V GND 3.3V), but the order differs between sellers. Read the silkscreen before applying power.
AMS1117 datasheet specs that matter
From the Advanced Monolithic Systems AMS1117 datasheet (3.3 V version). Many companies make a part called “AMS1117” and their datasheets differ, so check the one for the part you actually bought.
| Parameter | AMS1117-3.3 | What it means |
|---|---|---|
| Output voltage | 3.3 V ±2% (3.234–3.366 V) | Also 1.2, 1.5, 1.8, 2.5, 2.85, 5.0 V and ADJ |
| Output current | Up to 1 A | Heat limits you first |
| Dropout voltage | 1.3 V typ, 1.4 V max @ 1 A | Input must stay ~1.3 V above output |
| Quiescent current | 3 mA typ, 10 mA max | Flows even when your circuit sleeps |
| Line regulation | 0.15% typ (VIN up to 12 V) | Output barely moves as input changes |
| Load regulation | 0.2% typ (10 mA to 1 A) | Output barely moves with load |
| Ripple rejection | 70 dB typ @ 120 Hz | Good on mains hum |
| Output capacitor | 10 µF tantalum, ESR ≤ 0.5 Ω | Needed for stability |
| Thermal resistance | 150 °C/W (SOT-223, junction-ambient) | 0.5 W ≈ 75 °C rise without extra copper |
| Protection | Current limit, thermal shutdown 150 °C | On the datasheet; not always on unbranded parts (see below) |
| Junction temperature | −40 to 125 °C |
AMS1117 input voltage: minimum and maximum
| Version | Minimum input (≈ VOUT + 1.3 V) | Works from | Doesn’t work from |
|---|---|---|---|
| AMS1117-3.3 | ≈ 4.6 V | 5 V USB, 7–9 V adapters, 12 V at low current | One Li-ion cell (3.7 V), 3× AA |
| AMS1117-5.0 | ≈ 6.3 V | 7–12 V adapters | 5 V USB, 2-cell Li-ion when low |
Maximum input: the AMS datasheet specifies line regulation up to 12 V. Some unbranded “AMS1117” batches are rated lower (about 10 V), so check your part’s own datasheet. In practice the limit is heat: from 12 V, each 100 mA of load wastes 0.87 W.
How to wire an AMS1117 for 5 V to 3.3 V
Calculator: will it work, how hot, how long on battery?
Estimates from typical datasheet values. Temperature rise uses the package’s thermal resistance with minimal copper (SOT-223 ≈ 150 °C/W for AMS1117, 62 °C/W for LM1117; SOT-23 ≈ 224 °C/W). More copper or an aluminium PCB runs much cooler: our TrueVolt74033 runs 300 mA from 5 V on its aluminium PCB. Battery life ignores self-discharge and cut-off voltage.
Common AMS1117 problems
Gets hot
Heat = (VIN − 3.3 V) × current. From 5 V at 300 mA that’s 0.5 W; from 12 V, 2.6 W. Above ~0.5–1 W, use more copper or a buck converter.
Random resets
Only ~0.4 V margin from 5 V USB. Cable drops or relay switching push it into dropout and trip the brownout detector.
Battery dies fast
3 mA idle current flows all the time. With a sleeping MCU, the regulator becomes the biggest load. Try the battery tab above.
Low output on Li-ion
Needs ≈ 4.6 V in. A Li-ion cell sits near 3.7 V, so the output sags almost immediately.
Oscillation / ringing
Wrong output capacitor. Follow the ESR range in your part’s datasheet.
ESP32 brownouts
Espressif asks for a 3.3 V supply of at least 500 mA because Wi-Fi bursts are large. Low headroom makes it worse.
Is your AMS1117 genuine? Why it matters
Many companies sell a part called AMS1117, and an unbranded one may not behave like any datasheet:
- Measured failures. Engineer Gough Lui bench-tested unbranded AMS1117-3.3 parts bought in bulk online (2021). Most had no working thermal shutdown; when they overheated at roughly 1.3–1.9 W they failed with input shorted to output. He could not match the part to any datasheet. Read his test.
- Different ratings under one name. On the EEVblog forum, engineers report batches whose maker’s datasheet allowed only about 10 V input; at 12 V they failed shorted. See the discussion.
Related 3.3 V regulators
| Regulator | Max current | Dropout (typ) | Idle current | Max input | Best for |
|---|---|---|---|---|---|
| AMS1117-3.3 | 1 A | 1.3 V @ 1 A | 3 mA | 12 V | Mains/USB, loads above 300 mA |
| LM1117-3.3 (TI) | 800 mA | 1.2 V @ 800 mA | 5 mA | 15 V | AMS1117 use with a full TI datasheet |
| TLV740P-3.3 (TI) | 300 mA | 460 mV @ 300 mA | 50 µA | 5.5 V | 3.3 V rails up to 300 mA, battery-backed projects |
| AP2112K-3.3 (Diodes) | 600 mA | 250 mV @ 600 mA | 55 µA | 6 V | ESP32 with Wi-Fi from USB or Li-ion |
| MCP1700-3.3 (Microchip) | 250 mA | 178 mV @ 250 mA* | 1.6 µA | 6 V | Coin-cell, long-life sensors |
| HT7333 (Holtek) | 250 mA | 90 mV @ 40 mA | 3.5 µA | 12 V | Low-current battery, higher input |
| XC6206-3.3 (Torex) | ~200 mA | 250 mV @ 100 mA* | 1 µA | 6 V | Tiny, very low-power loads |
* Dropout given for a nearby voltage version in the datasheet (MCP1700 2.8 V, XC6206 3.0 V).
Frequently asked questions
Replace your AMS1117 module
TrueVolt74033: genuine TI TLV740P, 50 µA idle, 300 mA, reverse-current diode, aluminium PCB. Designed and assembled in Pune.
Sources: Advanced Monolithic Systems AMS1117 datasheet · TI LM1117 datasheet and TLV740P product page · Diodes Inc. AP2112 datasheet · Microchip MCP1700 datasheet · Holtek HT73xx datasheet · Torex XC6206 datasheet · Espressif ESP32 hardware design guidelines · Gough Lui, “When is an AMS1117 not an AMS1117?” (2021) · EEVblog forum, “AMS1117: are they all the same?”. Values typical unless stated.