NCE0102 Pin Diagram & Pin Functions

Pin order is not universal across SOT-23 MOSFETs. The NCE0102 uses 1-G / 2-S / 3-D, the common order for NCE and many vendors — but other manufacturers ship SOT-23 N-FETs with different arrangements, and a footprint copied from the wrong datasheet swaps drain and source silently.

Key Specifications (NCE0102, datasheet v4.2)

R_DS(on) at each gate drive voltage — what the datasheet actually guarantees:

What does 3.3V actually buy you? Conduction — but no guaranteed resistance. The threshold band is 1.2–2.5V, so a 3.3V gate turns the channel on; don't trust it for a full-rated 2A load, and don't compare 3.3V numbers against the 4.5V row.

Typical Application Circuit — Low-Side 48V Switch

Wire it by pin function, not by habit: pin 3 (drain) takes the load side, pin 2 (source) returns to ground, pin 1 (gate) gets the drive. The catch diode sits across the load with its cathode on the 48V bus.

Common Mistakes When Using the NCE0102

Mistake 1: Swapping drain and source against the footprint. Real SOT-23 layouts have shipped with pin 3 (drain) tied to ground and pin 2 (source) to the bus.

Why does the load stay on? Because the body diode then conducts permanently — gate drive never matters.

Check the footprint against THIS datasheet's pin order, not the library part name. A diode-mode measurement across pins 2-3 should read one diode drop in only one polarity.

Mistake 2: Assuming every SOT-23 MOSFET has the same pin order. The NCE0102 is 1-G / 2-S / 3-D, and many vendors match it — but not all do. When you swap a part from another manufacturer into this footprint, verify its datasheet pinout first.

Mistake 3: Leaving the gate floating. What does a floating gate do to your load? It charges up from leakage or noise and turns the FET on whenever it feels like it — at full bus voltage.

A 10k–100k pull-down from gate to ground holds it off while the MCU boots.

Mistake 4: Expecting the 2A sticker continuously. 2A at 229mΩ is 0.92W against a 1.25W budget on a 100°C/W path. Honest continuous duty on a real board is roughly 0.5–1A; above that, step to a bigger package before the board gets hot.

Mistake 5: Driving 3.3V and expecting a guaranteed 249mΩ. The threshold band is 1.2–2.5V, so 3.3V conducts — but R_DS(on) is only guaranteed at 4.5V and 10V. For light loads 3.3V works; for guaranteed resistance, drive from 5V logic or buffer it.

Mistake 6: Treating 2.45mJ E_AS as a free energy budget. A relay coil without a catch diode will exceed it on the first de-energize. Put the diode across the load, not across the FET.

Where to Buy the NCE0102

ICMASS stocks the NCE0102 in tape and reel, tested at the datasheet conditions (R_DS(on) 229mΩ max at 10V/2A, threshold inside 1.2–2.5V). Same-day shipping from Shenzhen; the 100V SOT-23 family — NCE0102, NCE0103Y and the TO-252 NCE0110AK — is on the same shelf for the step-up.

Frequently Asked Questions

Q1: What is the NCE0102 pinout?

A: Pin 1 = gate, pin 2 = source, pin 3 = drain. The part is a 100V/2A N-channel trench MOSFET in SOT-23 with marking “0102”. This is the common NCE order, but confirm against the datasheet before reusing a library footprint.

Q2: Can I drop it into a BSS123 or 2N7002 footprint?

A: Usually yes — but verify pin order first. The NCE0102 (1-G/2-S/3-D) matches the order used by many SOT-23 small-signal parts, but not all manufacturers use it. A swapped drain and source forward-biases the body diode and the load never turns off.

Q3: Why is my load always on after I installed the FET?

A: Check for a drain-source swap or a floating gate. If pin 3 (drain) is on the ground side, the body diode conducts permanently regardless of gate drive. If the gate has no pull-down, leakage or noise charges it and the FET conducts unexpectedly.

Q4: Can 3.3V logic drive this part?

A: It conducts, but resistance is only guaranteed from 4.5V. The threshold is 1.2–2.5V, so 3.3V turns the channel on for light loads. For a guaranteed 249mΩ max, drive from 5V logic or buffer the gate.

Q5: How much current can it really switch continuously?

A: Roughly 0.5–1A on a real board. The 2A rating at 25°C burns 0.92W against a 1.25W budget on a 100°C/W path — fine for a fan or relay, tight for steady loads in warm enclosures. Use it as a switch, not as a continuous 2A pass element.

Q6: Do I need a catch diode for a relay load?

A: Yes. The published E_AS of 2.45mJ is a single-pulse test number, not a free budget. A relay coil without a catch diode exceeds it and damages the FET; put the diode across the load, cathode on the supply rail.

Q7: How do I check the orientation with a multimeter?

A: Use diode mode between pins 2 and 3. The body diode should read roughly 0.4–0.7V in one polarity (anode at source, pin 2) and open in the other. If it conducts both ways or not at all, the part is damaged or the pins are misidentified.

Q8: What is the difference between NCE0102 and NCE0103Y?

A: Same 100V SOT-23 family, different dies. The 0102 is 2A/229mΩ with a lighter 12nC gate and a published 2.45mJ E_AS; the 0103Y is 3A/160mΩ with a 20A pulse rating and lower 1.0–2.0V threshold. For steady sub-1A duty the 0102 is the cheaper honest pick.