FDN337N – Datasheet, Fairchild, Alternative & Model onsemi

FDN337N-NL-VB an N-channel SOT23 package MOS tube

FDN337N

The FDN337N from ON Semiconductor is a compact, low-power N-channel MOSFET ideal for efficient switching and power management. It’s designed specifically for small, battery-powered gadgets or devices needing fast, reliable switching at low voltages.

With a maximum voltage rating of 30V and continuous current up to 2.2A, this transistor can handle typical portable-device requirements easily. Its low on-resistance of about 65mΩ means minimal power loss and excellent efficiency.

Thanks to a low gate threshold voltage (1.2 to 2.5V), controlling it directly with microcontrollers or logic circuits running at 3.3V or 5V is simple, no extra parts needed. The tiny SOT-23 package fits perfectly where board space is limited.

You’ll find the FDN337N useful in applications like phones, wearable devices, LED drivers, small motors, DC load switches, and anything powered by batteries that needs high efficiency and quick switching.

FDN337N Pinout Diagram

When wiring the FDN337N MOSFET, keep the gate voltage below ±20V to protect the device. Adding a small resistor (10-100Ω) at the gate helps prevent unwanted oscillations. The source typically connects to ground as the reference point, and the drain connects directly to your load, with the other load terminal going to the positive supply—just make sure the voltage and current stay within 30V and 2.2A limits. MOSFETs are sensitive to static electricity, so proper anti-static measures help keep them safe. For continuous high-current operation, good heat management is essential to avoid overheating issues.

FDN337N Equivalent MOSFET Transistor

When choosing a MOSFET to replace FDN337N, think about your application needs. For higher currents (above 1A), FDN337N (2.2A) or SI2302 (2.3A) work better. SI2302 also has lower R_DS(on) (45mΩ) compared to FDN337N (65mΩ), making it more efficient for high-performance circuits. Watch the gate voltage—2N7002 and BSS138 typically need at least 5V, so they’re not ideal for 3.3V logic circuits. All these alternatives use the SOT-23 package, so swapping them directly onto your board is simple. Pick SI2302 for fast switching and high efficiency, or 2N7002 for smaller currents and low-power applications.

FDN337N Switching Circuit Example

This circuit uses two MOSFETs to create a simple high-side power switch. A P-channel MOSFET (ZXMP3A16G) switches the main +18V power line, while an N-channel MOSFET (FDN337N) controls its gate.

When POWER_ON goes high, the FDN337N turns on, pulling the gate of ZXMP3A16G low and connecting +18V to the output. When POWER_ON is low, FDN337N switches off, and ZXMP3A16G’s gate rises, turning it off and disconnecting power.

The FDN337N makes switching fast and efficient. Keep resistor values (like R6, R7, R10) as shown for stable operation, and always check MOSFET ratings carefully, especially voltage limits and heat management.

FDN337N Load Switching Application

The FDN337N MOSFET is perfect as a load switch for low-voltage or battery-powered devices. It’s super easy to control directly from microcontrollers with 3.3V or 5V GPIO pins—no extra circuitry needed. Just feed a high-level signal to the gate, and it connects the load to ground, turning your device on. A low-level signal switches it off, cutting power.

With low on-resistance, it keeps power loss minimal and efficiency high. Fast switching means less wasted energy, especially useful for IoT devices, LEDs, relays, fans, and battery-powered equipment. Just keep within its voltage (30V) and current limits (2.2A), and consider diode protection for inductive loads.

FDN337N Gate Threshold Voltage

The gate threshold voltage (V_GS(th)) is the point where the FDN337N MOSFET just starts to turn on. Above about 2.5V, it fully switches on, giving the lowest resistance and best efficiency. If driving it directly with a microcontroller (3.3V or 5V GPIO), it’ll work great. For best results, use at least 4.5V to guarantee a solid connection and avoid unnecessary heat or power loss. Keep gate voltage comfortably above the threshold, because operating close to or below this limit can lead to poor performance. Also, remember temperature affects this threshold—build in some margin for reliability.

FDN337N Logic Level MOSFET Circuit

Here’s a simple MOSFET driver circuit you can use with logic-level MOSFETs like the FDN337N. Connect a 3.3V or 5V control signal directly to the MOSFET gate through a 2.2kΩ resistor (R1) to limit current spikes and protect your microcontroller pin. A 10kΩ resistor (R2) pulls the gate down, ensuring the MOSFET stays off without a control signal.

When the gate sees more than about 1.6V, the MOSFET switches on, powering your load—perfect for LEDs, relays, or fans. It’s straightforward, low-cost, reliable, and great for beginners or quick prototyping without additional components.