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SOT-223 · AMS1117-3.3
ActiveLinear Voltage Regulators (LDO)
AMS1117-3.3
Advanced Monolithic Systems · SOT-223 · Linear Voltage Regulators (LDO)
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Overview
The AMS1117-3.3 is the fixed 3.3 V variant of the AMS1117 low-dropout positive voltage regulator family from Advanced Monolithic Systems, delivering up to 1 A of output current with a typical dropout voltage of 1.1 V at 800 mA. It is pin-compatible with the industry-standard LM1117 and the older LT1117, which makes it a common second source in 5 V-to-3.3 V post-regulation on Arduino clones, ESP8266/ESP32 development boards, router modems and countless industrial controllers.
The internal architecture uses a PNP pass transistor rather than the classic NPN Darlington of the LM7805, which is what enables the low dropout. Protection circuitry includes current limiting (typically 1.2 A) and thermal shutdown at 150 °C junction temperature. Output stability requires a minimum 10 µF tantalum or 22 µF ceramic capacitor at the output; without it the regulator will oscillate under transient loads.
Key specs to keep in mind: input voltage range 4.5 V to 15 V (up to 20 V absolute max), quiescent current 5-8 mA (higher than modern low-Iq LDOs), and output tolerance ±1.5% over line and load. Thermal performance in the SOT-223 package gives 60 °C/W junction-to-ambient, so at 800 mA and 5 V in / 3.3 V out you dissipate about 1.36 W and hit 82 °C rise — attach a copper plane on the PCB or derate the current.
For battery-powered designs, prefer the HT7533 (4 µA quiescent) or MCP1700 (1.6 µA). For higher currents, look at the AZ1117-3.3 (1 A) or the switching TPS54331 (3 A buck).
Shenzhen stock is deep — AMS1117-3.3 is one of the highest-volume LDOs in Asia. MOQ 1 reel (2,500 pcs SOT-223) or 100 pcs loose for prototyping.
Key Features
- Fixed 3.3 V output at up to 1 A
- Low dropout: 1.1 V typ at 800 mA
- Pin-compatible with LM1117 and LT1117
- Internal current limit + thermal shutdown
Typical Applications
- Post-regulation from 5 V USB to 3.3 V logic on ESP32/ESP8266 boards
- Arduino and Raspberry Pi HAT power rails
- Industrial controller 3.3 V supply from 12 V or 24 V rails (with pre-regulator)
- Networking and telecom line cards
- Consumer appliances needing a simple, robust 3.3 V rail
Specifications
- Output Voltage
- 3.3 V
- Output Current
- 1 A
- Dropout Voltage
- 1.3 V
- Input Voltage (Max)
- 15 V
- Line Regulation
- 0.2 %
- Operating Temperature
- -40 to 125 °C
- Mounting Type
- Surface Mount
- Pins
- 3
- RoHS
- Compliant
Procurement Tips
For battery-powered products, replace AMS1117-3.3 with HT7533 or MCP1700 — the 4-6 µA quiescent current extends battery life by months in standby-heavy applications.
Frequently Asked Questions
What's the difference between AMS1117-3.3 and LM1117MP-3.3?
Functionally identical — same pinout, same SOT-223 package, same 3.3 V output at 1 A. AMS1117 is Advanced Monolithic Systems (a Chinese-US joint venture), LM1117 is TI's version. AMS1117 is significantly cheaper and widely used in Asia; LM1117 has tighter spec guarantees and broader temperature range.
Why does my AMS1117 get very hot?
Linear regulators dissipate (Vin - Vout) × Iout as heat. At 5 V in, 3.3 V out, 800 mA load, that's 1.36 W. In SOT-223 with 60 °C/W, junction rises 82 °C above ambient. Add a copper pour under the tab pin, or switch to a buck converter (TPS54331) for higher currents.
Can I use it with 12 V input?
Yes up to 15 V nominal (20 V absolute max), but at 12 V in / 3.3 V out and 500 mA you dissipate 4.35 W — far beyond what SOT-223 can handle without a heatsink. Use a switching regulator like the LM2596 or TPS54331 instead.
What capacitor do I need on input and output?
Datasheet requires 10 µF tantalum minimum on output for stability, plus 100 nF ceramic for high-frequency bypass. Input needs at least 10 µF if the source is more than 6 inches away. Modern ceramic MLCCs work too — use 22 µF X5R 0805 on output.
Is it counterfeit-prone?
Somewhat. AMS1117 is one of the most-cloned regulators. Genuine parts have laser etching, matte tin leads, and consistent weight. Fakes may output 3.0 V instead of 3.3 V or fail at 800 mA. Test a sample with a load bank before mass production.
MOQ and lead time?
MOQ 2,500 pcs on reel for AMS1117-3.3 (SOT-223), or 100 pcs loose. Shenzhen stock ships in 1-2 days.
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