NCP1117ST33T3G — 3.3V/1A Commercial LDO, SOT-223

What Are the Technical Specifications of NCP1117ST33T3G?

Key numbers that matter. 1A output in SOT-223 sounds impressive until you do the thermal math. At 1A with a 5V input (1.7V dropout), the NCP1117 dissipates 1.7W. With R_θJA of 70–90°C/W on reasonable copper, that's a 119–153°C rise. Junction hits 144–178°C at 25°C ambient. Thermal shutdown trips near 175°C.

The takeaway: you can't run 1A at high dropout without serious PCB copper or a heatsink. This LDO is happiest when the input voltage sits close to the output.

The second thing: 10mA Iq. An NCV4264 at 33µA draws 0.3% of that. For a USB-powered gadget, who cares. For a battery-backed RTC, it's 300× the drain on your coin cell.

When Should You Use (and NOT Use) the NCP1117?

What Are the Alternatives to NCP1117ST33T3G?

NCP1117 vs NCV automotive LDOs — the decision in two questions. First: does your device run from a battery? If yes, the 1117's 10mA Iq rules it out. Second: does it live outdoors or in a vehicle? If yes, the 0°C floor and lack of reverse-battery protection rule it out.

If both answers are no — a mains-powered, indoor, consumer or industrial product — the NCP1117 gives you 1A output at the lowest cost in its class.

What Are the Typical Applications of NCP1117?

Consumer electronics post-regulation. A 5V USB or barrel-jack supply feeds the NCP1117, which drops it to a clean 3.3V for the main MCU, Wi-Fi module, and sensor array. 800mA typical load, 1.7V dropout, 1.36W dissipation. Spread across a 4-layer board's ground plane, the SOT-223 stays under 100°C junction rise.

Router, set-top box, and smart home hub power tree. These devices almost all run the same pattern: 12V or 5V wall adapter → 3.3V LDO for the SoC → additional rails for DDR, I/O, and RF. The NCP1117 at 3.3V/1A is the workhorse for the main logic rail.

Industrial HMI and PLC auxiliary rails. Factory-floor HMIs and PLC I/O modules don't face -40°C cold starts, but need reliable regulation for 5–10 year service lives. The NCP1117's SOA protection and thermal shutdown cover the basics. For 24V industrial inputs, add a pre-regulator to drop the voltage into range.

3D printer controller boards. Most open-source 3D printer controllers (RAMPS, SKR, MKS) use a 1117-family LDO to generate 3.3V from a 5V or 12V rail for the MCU. The NCP1117ST33T3G fits the same SOT-223 footprint and costs pennies.

Why Buy NCP1117 from ICMASS?

We stock the whole 1117 family. Fixed 1.8V, 2.5V, 3.3V, 5.0V, and the adjustable version. If your design uses multiple rails, one order covers all of them.

Genuine onsemi parts with traceability. The 1117 is one of the most counterfeited LDOs in the market. A remarked clone might output 3.3V at 100mA but drop to 2.8V at 800mA because the pass transistor is undersized. We ship factory-original parts with date-code traceability.

Cross-reference: 1117 variants from TI, ST, and Diodes Inc. Not sure which 1117 your BOM actually needs? We'll match the exact manufacturer part number, or recommend the active-production equivalent if your original has gone EOL.

Shenzhen warehouse, global DHL/FedEx. Same-day shipping before 15:00 CST. Contact us for a quote on your volume.

Frequently Asked Questions About NCP1117ST33T3G

Q1: Can NCP1117ST33T3G replace an LM1117MPX-3.3?

A: Yes, in most designs. Same package (SOT-223), same 3.3V output, same pinout. The NCP1117 is rated for 1A vs the LM1117's 800mA, giving you slightly more headroom. Both drop about 1.1–1.2V at rated load. Check the output capacitor requirements: both need a 10µF tantalum on the output with some ESR for stability.

Q2: Why does the NCP1117 get so hot at 1A?

A: It's simple physics. 1A × dropout voltage = watts of heat. At 5V in, 3.3V out, and 1A load, the NCP1117 dissipates 1.7W. The SOT-223 package has a junction-to-ambient thermal resistance of 70–90°C/W. That's a 119–153°C rise. At 25°C ambient, the junction reaches 144–178°C. The fix: keep the input voltage close to the output, maximize PCB copper area on the tab, or use a small heatsink on the SOT-223 body.

Q3: What's the difference between NCP1117ST33T3G and NCP1117LPST33T3G?

A: The LP version drops quiescent current from 10mA to 700µA. Everything else is the same. Same 3.3V/1A, same SOT-223, same pinout. If your device is always on or has any battery life consideration, use the LP version. The standard NCP1117 makes sense only when cost is the sole driver and the device is mains-powered.

Q4: Can I use NCP1117 in a car?

A: Not recommended. The minimum operating temperature is 0°C, and there's no reverse-battery protection. A winter cold-start drops the cabin temperature below freezing. Connect a jump-starter backwards and the NCP1117 is destroyed. For automotive, use the NCV4264 (100mA), NCV4266 (150mA, with EN), or NCV8664 (150mA, lowest Iq). All are AEC-Q100 qualified with -42V reverse-battery protection.

Q5: Does the NCP1117 need a heatsink?

A: Depends on the power dissipation. At <0.5W, PCB copper alone is enough. Above 1W, you need significant copper area or a heatsink. The SOT-223's exposed tab is designed to be soldered to a copper plane. With 500mm² of 1oz copper, R_θJA drops to about 50°C/W. At 1W dissipation, that's a 50°C rise — fine at 40°C ambient. At 2W, you're at 100°C rise + 40°C ambient = 140°C junction. Getting close to the 150°C limit.

Q6: What output capacitor should I use with NCP1117?

A: 10µF tantalum minimum on the output. A 22µF X7R ceramic with a small series resistor also works. The NCP1117 needs some ESR for loop stability. Modern MLCCs with sub-10mΩ ESR can push the control loop into oscillation. If using a ceramic capacitor, add a 0.5–1Ω resistor in series, or use a capacitor specifically characterized for LDO stability.

Q7: NCP1117 vs NCV4264 — which one for a 3.3V rail?

A: Two questions decide it. How much current? Is it automotive? If you need 100mA or less and it's going in a vehicle, the NCV4264 wins (33µA Iq, 45V input, AEC-Q100). If you need 1A and it's a commercial/indoor product, the NCP1117 wins (lower cost, 10× the current). They share a package but not a use case.

Q8: Is the NCP1117 available in a through-hole version?

A: The NCP1117ST33T3G is SMD only (SOT-223). For through-hole, use the LM1117T-3.3 (TO-220) or LD1117V33 (TO-220). The SOT-223 is easy to hand-solder and widely used on SMD adapter boards. If you're breadboarding, get a SOT-223 breakout board rather than searching for a DIP-packaged 1117 — they're rare and cost 5× more.

Related Products

• NCV4266-2CST50T3G — 5V/150mA Automotive LDO with Enable, SOT-223-4
• NCV4264-2CST33T3G — 3.3V/100mA Automotive LDO, Ultra-Low Iq, SOT-223-3
• NCP1117LPST33T3G — Low-Power 3.3V/1A LDO, Same Pinout, 700µA Iq
• NCV4266 vs NCV4264 vs NCP1117 — Automotive vs Commercial LDO Selection Guide