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SOT-223 · AMS1117-2.5
Active1A LDO Regulator (2.5V)
AMS1117-2.5
Advanced Monolithic Systems · SOT-223 · 1A LDO Regulator (2.5V)
Price on Request
Get a competitive quote within 24 hours. Volume discounts available. Shenzhen stock ships in 1-2 business days.
Overview
The AMS1117-2.5 provides a fixed 2.5 V rail at up to 1 A from the same SOT-223 1117 die family as the 1.8 V, 3.3 V and 5.0 V versions, and it occupies a useful niche: 2.5 V is a common analogue supply, VCO and reference rail, and it is also the standard voltage for a precision external reference in data converters. The regulator uses a PNP pass transistor referenced to a Zener-trimmed bandgap, so dropout is 1.1 V typical at 800 mA and about 1.15 V to 1.3 V at 1 A, meaning the input must stay above roughly 3.9 V for full-load operation. Line regulation is 0.2% maximum and load regulation 0.4% maximum over the family, with output accuracy near ±1% at 25 °C.
Protection and stability behaviour match the rest of the family. On-chip current limiting around 1.2 A to 1.5 A and thermal shutdown near 150 °C junction guard against shorts and blocked airflow, and a minimum 10 µF low-ESR output capacitor — 22 µF X5R ceramic in modern layouts — is required for loop stability. Ground-pin current is the weak point for battery work: 5 mA typical and 10 mA maximum regardless of load, so a sleeping node drawing 100 µA elsewhere will see its runtime dominated by the regulator. Where quiescent current matters, a micropower LDO such as the MCP1700-250 or ME6211C25 is the better choice, at the cost of a lower current ceiling.
Thermal derating governs the real current limit. SOT-223 junction-to-ambient is around 60 °C/W on a modest pad, and the tab is the only heat path, so a 5 V to 2.5 V conversion at 1 A dissipates 2.5 W plus ground current and cannot be sustained without a substantial copper pour and vias. At 400 mA the same conversion is 1 W, which is comfortable. Compute (VIN - VOUT) x IOUT + VIN x IGND and compare against the junction budget before fixing the layout, and if the drop is large, use a buck converter such as the MP1584EN followed by this LDO for a low-noise 2.5 V rail — a hybrid that keeps both efficiency and ripple low.
For procurement, the AMS1117-2.5 is interchangeable in footprint and pinout with LM1117-2.5, AZ1117-2.5 and SPX1117-2.5, which gives a healthy second-source pool and stable pricing in the single-digit cent range at reel quantities. The flip side is a busy remarking market: 2.5 V is a lower-volume variant than 3.3 V, so brokers often relabel the ubiquitous AMS1117-3.3 or even an adjustable unit with the wrong top mark. Incoming inspection should verify the output voltage under a 500 mA load, measure ground current, and confirm dropout by pulling the input down to 3.9 V. Our Shenzhen stock ships in one to two business days with MOQ of 100 pcs loose or 2,500 pcs on tape-and-reel; we sample-test every lot and can provide a certificate of conformance and reel photographs on request.
Key Features
- Fixed 2.5 V at up to 1 A in a pin-compatible SOT-223 outline
- 1.1 V typical dropout at 800 mA from a 3.9 V minimum input
- 0.2% line and 0.4% load regulation with ±1% initial accuracy
- Current limiting and thermal shutdown integrated on chip
- Drop-in second source for LM1117-2.5, AZ1117-2.5 and SPX1117-2.5
Typical Applications
- Precision analogue and data-converter reference supplies
- VCO, PLL and RF front-end bias rails in communications hardware
- Sensor signal-conditioning circuits needing a quiet 2.5 V domain
- 2.5 V logic and I/O rails on mixed-signal boards
- Test equipment, medical instruments and calibration fixtures
Specifications
- Output Voltage
- 2.5 V
- Input Voltage
- 3.9 to 15 V
- Output Current (Max)
- 1 A
- Dropout Voltage (Typ, IOUT = 800 mA)
- 1.1 V
- Quiescent Current (Max)
- 10 mA
- Line Regulation (Max)
- 0.2 %
- Load Regulation (Max)
- 0.4 %
- Output Capacitor (Min for Stability)
- 10 µF
- Pins
- 3
- RoHS
- Compliant
Procurement Tips
If this rail feeds a data converter, order the regulator together with a low-noise ferrite bead and a 22 µF ceramic plus 100 nF decoupling pair, and consider a dedicated reference device — buying the LDO alone is the most common cause of noisy 2.5 V analogue rails we see in first-article builds.
Frequently Asked Questions
Should I use an AMS1117-2.5 or an external voltage reference such as the LM4040?
Different jobs. The AMS1117-2.5 is a power regulator: it can source 1 A, has 0.2% to 0.4% regulation and a few millivolts of broadband noise, which suits supplying chips. A shunt reference such as the LM4040 or REF3025 is a precision element with 0.05% to 0.2% initial accuracy, low temperature drift (25 ppm/°C to 100 ppm/°C) and only a few milliamps of capability, intended to set an ADC's full scale. Best practice on a precision board is a regulator for the analogue rail plus a dedicated reference for the converter, with the reference decoupled properly.
What is the minimum input voltage for the 2.5 V version?
About 3.9 V to hold full-load regulation: 2.5 V output plus the 1.1 V typical dropout at 800 mA, plus margin for input sag and capacitor ripple. At lighter loads the dropout falls to roughly 0.9 V to 1.0 V, so a 3.6 V rail can still work below about 300 mA. Do not plan a 3.3 V input — that leaves no headroom and the output will collapse under load transients.
Why is the output 2.55 V or 2.45 V instead of exactly 2.5 V?
Within specification. Initial accuracy is about ±1% at 25 °C, and line and load regulation add up to 0.2% and 0.4% respectively, so 2.45 V to 2.55 V over the full operating range is normal. If you measure outside that window, suspect a counterfeit or remarked part, an open or wrong output capacitor causing oscillation (measure with a scope, not just a meter), or excessive trace resistance between the regulator and the measurement point.
How does the AMS1117-2.5 compare with a switching converter for this rail?
The LDO wins on noise, size at low current and cost below about 300 mA. A buck converter wins above roughly 400 mA or whenever the input-to-output differential exceeds 1.5 V to 2 V, because the LDO wastes (VIN - VOUT) x IOUT as heat. The common compromise in 2.5 V analogue designs is a buck to 3.3 V or 4 V followed by this LDO: the switcher handles the bulk power efficiently and the LDO cleans up switching residue to give a low-noise 2.5 V rail.
Is this part counterfeit-prone, and how do I check incoming stock?
Yes, the 1117 family is heavily remarked, and the 2.5 V variant is a favourite target because it is less common than 3.3 V. Physically, look for laser-etched marking with consistent font and date code, matte tin leads and clean moulding; ink that lifts with solvent is a reject. Electrically, load each sample at 500 mA and confirm 2.5 V ±2%, measure ground current (5 mA to 10 mA), and lower the input to 3.9 V to verify regulation holds. We perform this test on samples from every reel and ship with a C-of-C.
What is the MOQ and lead time?
MOQ is 100 pcs loose or 2,500 pcs on tape-and-reel in SOT-223. Shenzhen stock ships in one to two business days. If you need a qualified second source, Diodes Incorporated AZ1117-2.5 and TI LM1117MPX-2.5 are footprint-identical and available through authorised channels in four to ten weeks.
Alternatives & Equivalents
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