IRLZ44N MOSFET Overheat and Fail in 12V Motor Control Circuit?

Hi there!

Thanks for reaching out. I’ll forward this to my team for review and will get back to you with an update as soon as possible.

Best regards,
Amina

Hello there,

Dizar here, and I’m happy to help with your question!

You’re absolutely on the right track in suspecting multiple contributing factors. While the IRLZ44N is rated for high current, it performs reliably only under ideal conditions. Several common issues can lead to overheating or even failure.

Here are the key areas I recommend checking:

- Gate Drive Voltage and Current: Although the IRLZ44N is a logic-level MOSFET, it still requires a gate voltage of 10–12V for full enhancement. If you’re driving it directly from a 5V microcontroller, I strongly recommend using a gate driver such as the IR2104 or TC4420 to ensure fast and complete switching.
- PCB Layout and Trace Width: Traces that are only 1mm wide are typically insufficient for handling high current. I suggest increasing trace width significantly or using large copper pours or parallel traces. If your board uses 1 oz copper, upgrading to 2 oz copper can help reduce resistance and heat buildup.
- Thermal Dissipation: A small heatsink may not be enough. Even at a low R_DS(on) of 5 mΩ, 47A can generate over 11W of heat, which must be properly dissipated. A larger heatsink, good thermal interface material, and possibly forced airflow could improve reliability.
- Source Pin Grounding: Ensure the MOSFET’s source pin connects to ground using wide copper areas, minimizing parasitic inductance and improving both thermal and electrical performance.
- Flyback Protection: Since you’re switching a motor, don’t forget to place a Schottky flyback diode across the motor terminals to suppress inductive voltage spikes.
- Saturation Check: If possible, use an oscilloscope to monitor V_DS during operation to ensure the MOSFET is fully turning on.
- Rare Component Variance: Though unlikely, it's worth trying a second MOSFET from a different batch or supplier. I’ve encountered rare cases where individual components behaved unexpectedly due to subtle manufacturing issues.

I hope these suggestions help you get to the root of the problem. If the issue persists, feel free to share a portion of your schematic or PCB layout, I'd be happy to take a closer look.

All the best,
Dizar

Hi there,

It sounds like you're hitting a few classic issues that can definitely cause overheating and early failure in power MOSFETs like the IRLZ44N — even though it's rated for 47A, that number assumes ideal conditions which rarely apply in a real-world setup.

A few things to check:

Gate Drive Voltage & Current: The IRLZ44N is a logic-level MOSFET, but it still needs a solid 10V gate drive for fully enhanced operation under high current. If your microcontroller or driver is only outputting 3.3V or 5V with limited current, the MOSFET might not be turning on fully, leading to high R_DS(on) and heating.

PCB Trace Width: 1mm traces are too narrow for anything close to 47A — even a few amps can cause significant heating, especially over long runs. Consider using wider traces, copper pours, or multiple layers for current carrying. There are calculators online (like IPC-2221) to estimate safe current capacity for your trace width.

Heatsink & Thermal Interface: A "small" heatsink might not be enough if you're switching large currents or doing PWM. Also check that you're using good thermal paste and ensuring solid mechanical contact. Sometimes adding a fan makes a big difference.

Switching Losses: If you're running at high switching frequencies without a proper gate driver (e.g., direct from GPIO), switching losses can spike due to slow transitions. Consider using a dedicated gate driver IC to speed things up and reduce heat.

We’ve seen similar scenarios with customers sourcing power MOSFETs for motor control and battery applications. If you’re looking for components that are better optimized for thermal performance or need advice on robust layout practices, feel free to check out our selection. https://www.ichome.com/

Hope this helps — happy to take a look at your schematic/layout if you want to share more details!

Best,

Hello Xiaonia,

Thank you for sharing these valuable insights and best practices for avoiding overheating and failure in power MOSFETs. Your detailed explanation on gate drive requirements, PCB trace width, thermal considerations, and switching losses is extremely helpful, not just for us, but for the broader community as well.

We truly appreciate your effort in highlighting the real-world limitations and offering practical solutions. If there's anything you need from our side to support your work or further assist others, please don't hesitate to reach out. We're always here to help.

Best regards,
Dizar