NCE4009S — 40V/9A N-Channel Power MOSFET (SOP-8)

What Are the Technical Specifications of NCE4009S?

Key numbers that matter: per the NCE4009S datasheet (v1.0), R_DS(on) is guaranteed at two gate voltages — 16mΩ max at 10V/8A and 24mΩ max at 4.5V/4A. The 4.5V row is tested at 4A, half the 10V test current, which is normal for a part that saturates late.

Why does the 2W envelope matter? 2W at 62.5°C/W puts the junction at 150°C in a 25°C room — and that 62.5°C/W assumes the test board's copper. Real boards with small drain pads land higher, so the honest continuous budget sits below 2W.

The avalanche absence is worth knowing: no E_AS number is published for this die. Treat avalanche as unprotected — for inductive loads, keep a freewheeling clamp path and step up to the NCE4012S or NCE4015S for a die with a characterized avalanche rating.

When Should You Use (and NOT Use) the NCE4009S?

✅ Use NCE4009S when:

• 24V-rail low-side switching. A 24V lead-acid system floats at 28.8V — a 30V part has under 1.2V of headroom left. 40V is the class that actually fits 24V industrial loads: relays, valves, fans, and small motors on clean regulated rails.
• Fast-switching small loads where gate charge is the tax. 22.9nC and 964pF C_iss are the lightest numbers in the 40V SOP-8 family — a 5V MCU GPIO or a small driver switches this die into the hundreds of kHz without breaking a sweat.
• 5V-logic load switches. R_DS(on) is guaranteed at 4.5V, so a 5V rail or GPIO drives it fully enhanced. This is a 5V-logic part, not a 3.3V one.
• Level-shifted high-side arrangements. The datasheet itself notes the part pairs with a complementary P-channel MOSFET to form a level-shifted high-side switch — no bootstrap capacitor needed in the N+P arrangement.
• Replacing legacy 40V SO-8 sockets. AO4480-class boards (40V/14A era) downsize to this die where the load never used the full 14A — same pinout, lighter gate load, lower cost.

❌ Don't use NCE4009S when:

• Sustained current near 9A. 9A at 16mΩ is 1.3W of conduction loss — two-thirds of the 2W envelope before switching loss, and the 62.5°C/W number assumes good board copper. Without drain copper and vias, this part runs hot above 5A.
• Driving from a 3.3V MCU GPIO. R_DS(on) is only specified at 4.5V and 10V. A 3.3V rail sits below both guarantee points — use a 2.5V-specified part or add a gate driver.
• Conduction-loss-critical designs above 5A. At equal current the bigger family dies run cooler: the 4009S is the entry die, not the power die. If the board lives at 6-9A continuous, step to the NCE4012S or NCE4015S — same pinout, no redesign.
• Unclamped automotive load dump. 40V covers switching overshoot on a 12V bus, but a real unclamped load-dump pulse (ISO 7637-2 test 5) can exceed 40V. Add a TVS clamp or a higher-rated part near the alternator.
• Repeated hot-plug shorts at the current limit. The 40A pulse rating handles inrush inside the lead frame's limits, but repeated short-circuit hot-plugs need a part with a published SOA curve you can design against.

What Are the Alternatives to NCE4009S?

The 40V SOP-8 decision in one line: the 4009S is the entry die — lightest gate charge, highest R_DS(on) of the family — so it wins where the load is small and switching is fast, and loses where conduction loss dominates.

Here's the thing to check before substitution: the drive-voltage row. An AO4480-era socket that ran at 10V gate drive takes the 4009S directly; a socket that relied on a 2.5V row of a 30V part like the AO4406 does not — the 4009S only guarantees 4.5V and 10V.

From what we see in Shenzhen (2025–2026), 40V SO-8 sockets migrate to parts like this for cost, and the migration fails most often when the old part was driven at 2.5V or 3.3V. Same pinout, different guarantee row.

What Are the Typical Applications of NCE4009S?

24V industrial load switching: A 24V PLC or valve board switches relays and solenoids through the 4009S — the 40V rating clears the 28.8V float voltage with real margin, and the 4.5V guarantee works with the 5V logic those boards carry.

12V systems with switching overshoot: DC motors, fans, and hot-plug loads on a 12V bus ring above 12V when they switch. The 40V rating absorbs the overshoot that a 20V or 30V part would die on — the headroom the design reviews on StackExchange keep telling beginners to buy.

Backlight and small LED driver stages: The dianyuan.com selection threads for this 40V SOP-8 class list backlight and small DC-DC stages as the volume sockets — the light 22.9nC gate charge keeps the drive stage simple at PWM frequencies.

Level-shifted high-side switches: Paired with a P-channel part, the NCE4009S forms the low-side half of an N+P high-side arrangement — the datasheet's own description — for battery-powered boards that want no bootstrap capacitor.

Compact 24V DC-DC auxiliary rails: Low-power buck stages and secondary switches at 1-3A sit inside the 2W envelope with margin, where the small die's low capacitance keeps switching loss down at higher frequencies.

Why Buy NCE4009S from ICMASS?

Every lot tested at both drive points. We batch-test R_DS(on) at 10V and 4.5V against the datasheet maxes before shipping. A remarked part from a smaller die fails the 4.5V/4A check by a wide margin — the fastest way to catch counterfeits in this class.

Origin verified against look-alikes. NCE's 40V line is a re-marking target — parts sold under near-identical names with a brand suffix are not Wuxi NCE origin. We confirm marking, package, and die behavior before the part goes on the shelf.

Cross-reference support for the whole NCE family. Not sure whether your board wants the 4009S, the 4012S, or the 4015S? Send us load current, gate drive voltage, and board copper — we'll tell you which die your design actually needs.

Same-day dispatch, 5-10 days worldwide. Orders before 15:00 CST ship same day via DHL or FedEx. For volume orders, we source directly from the NCE factory line.

Frequently Asked Questions About NCE4009S

Q1: Can it really carry 9A continuous?

A: Only with the PCB copper to move the heat. The datasheet derates to 6.4A at 100°C, and the package is rated 2W at 62.5°C/W. At 9A and 16mΩ the conduction loss alone is 1.3W — an 81°C rise in a 25°C room on the datasheet's board. With real drain copper and vias, the honest continuous envelope is 4-6A depending on ambient.

Q2: Is it a logic-level MOSFET? Can a 3.3V GPIO drive it?

A: It's a 4.5V-specified part — a 5V-logic MOSFET, not a 3.3V one. R_DS(on) is guaranteed at 4.5V and 10V only. Gate threshold runs up to 2V, so a 3.3V rail sits above threshold but below any guaranteed R_DS(on) point. For 3.3V systems, pick a part specified at 2.5V or add a gate driver.

Q3: Can I drop it into an AO4480 or AO4406 socket?

A: Yes into an AO4480 socket — with one check into an AO4406 one. All three share the SO-8 pinout: pins 1-3 Source, pin 4 Gate, pins 5-8 Drain. AO4480 is 40V like this part, so the drop-in is the R_DS(on) row — 16mΩ max here vs ~11.5mΩ there, fine for lighter loads. AO4406 is a 30V part — same footprint, but only where the rail never exceeds 30V.

Q4: Why is the 4.5V R_DS(on) tested at 4A instead of 8A?

A: Because before full saturation, on-resistance rises with current. The 4.5V row is measured at I_D = 4A, and the output characteristics show why: below full 10V gate drive the die isn't fully enhanced, so R_DS at high current and 4.5V reads higher than the 24mΩ max. Design at 4.5V for loads near 4A, or drive at 10V for the full rating.

Q5: How hot will it run at 3A, 6A, or 9A?

A: Work the numbers from the datasheet max. 3A at 16mΩ is 0.14W — a 9°C rise at 62.5°C/W. 6A is 0.58W, a 36°C rise. 9A is 1.3W, an 81°C rise — fine on paper, tight on a real board where steady-state SO-8 thermal resistance lands higher than 62.5°C/W without generous copper.

Q6: Why pick the 9A part when the 15A family step exists?

A: Gate charge, price, and load reality. The 4009S carries 22.9nC against the family's heavier dies — cheaper to drive, cheaper to buy, and at loads under 3A the R_DS(on) difference costs a few tens of milliwatts. The bigger dies earn their keep only when conduction loss dominates. Pick the die for the actual load, not the sticker.

Q7: What does the datasheet mean by "level shifted high side switch"?

A: Pair it with a P-channel MOSFET for a high-side switch without a bootstrap. In the classic N+P arrangement the P-channel sits high-side and this N-channel does the level shifting on the gate drive, so the logic ground-reference stays intact. That's why the datasheet description mentions complementary MOSFETs — the two halves are meant to work as a pair.

Q8: How do I verify a genuine NCE4009S?

A: Measure R_DS(on) at both drive points and check the marking. A genuine part reads within the 16mΩ (10V/8A) and 24mΩ (4.5V/4A) maxes. Remarked parts from smaller dies fail the 4.5V check badly. Watch for look-alike suffixes — parts named NCE4009S plus a brand suffix are copies, not Wuxi NCE origin.

Q9: Is 40V enough for automotive?

A: For switching overshoot on a 12V bus, yes — for unclamped load dump, no. Load-switch overshoot and ringing sit inside 40V with comfortable margin, which is why the design guidance recommends 40-60V parts to beginners on 12V systems. A real unclamped alternator load-dump pulse can exceed 40V, so anything near the alternator still needs a TVS clamp.

Q10: Which applications actually buy this part?

A: 24V industrial boards, 12V load switches, and compact DC-DC stages. From what we see in Shenzhen (2025–2026), the 40V/9A SO-8 class goes into valve and relay boards, motor and fan switches, and small power stages — where a 30V part is too thin for the rail and a 60V part is overkill.