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SparkFun MOSFET Power Switch and Buck Regulator (Low-Side)
Does your microcontroller need to control a high-voltage item, like a 12V LED strip, while also needing to be powered? Do you want to avoid having multiple power adapters and microcontrollers for your project? The MOSFET Power Switch and Buck Regulator (Low-Side) is one product we needed at SparkFun, so we figured other folks might have the same problem. Power the board with up to 12V and control up to 10A, all while providing a sweet 3.3V to your control board.
The SparkFun MOSFET Power Switch and Buck Regulator (Low-Side) combines two circuits into one board: an LMR14203 buck regulator configured to output 3.3V and an N-channel MOSFET (PSMN7R0-100BS) configured as a low-side switch. A flyback diode is also on the load side for devices with back EMF! Simply pull the CTL pin low to activate the load.
Various connectors (barrel jack, female header, and poke-home) are provided to connect a power supply to a microcontroller of your choice (Arduino, micro-bit, Raspberry Pi’s microcontroller) and load them together. VCC, 3.3V, CTL, and GND are also broken out through 0.1" spaced PTHs for those who prefer to solder. Two LEDs (PWR_LED and ON_LED) indicate when there is 3.3V and whenever power is applied to the load. Jumpers are included on the back to disable the LEDs. A MEAS PTH jumper is also included for those interested in precisely measuring the current consumption of the system.
Note: While the MOSFET is rated to 100A/100V, we don't recommend you go much above 10A as the PCB polygon pours and traces become the limiter.
- Input Voltage Range: 4.5V to 12V
- LMR14203 Step Down Voltage Regulator
- Configured to Output 3.3V/300mA
- PSMN7R0-1000BS N-Channel MOSFET
- Configured as a Low-Side Switch
- Connectors
- Input: 5.5mm x 2.1mm Barrel Jack (Center-Positive)
- Output: Poke-Home Connectors
- Control: 1x4 Female Headers
- 0.1"-spaced PTHs
- Built-in Flyback Diode on Load
- LEDs
- PWR
- ON
- Jumpers
- PWR_LED
- MEAS
- ON_LED
- Dimensions: 1.50" x 1.50" (38.1mm x 38.1mm)
- Weight: 9.9g
SparkFun MOSFET Power Switch and Buck Regulator (Low-Side) Product Help and Resources
Understanding Thermal Resistance
May 14, 2020
Discussing what thermal resistance is, how it’s used for thermal management, and how to maximize the life of your project.
Fading with the MOSFET Power Switch and Buck Regulator
July 1, 2024
In this tutorial, we will slowly turn on the load and then slowly turn it off using the N-channel MOSFET.
Comments
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Customer Reviews
4 out of 5
Based on 2 ratings:
Worked great, got me out of a pinch
For three years my arduino chicken coop door kept the girls safe but the major design flaw (me not being a power engineer) was that the CPU and the relay coils had to be powered by batteries. If they ran low, the birds would have to be let out manually. The thing broke down finally just before I had to travel.
This little breakout board made it possible for me to whip up a new version that would never run out of juice. The only problem I had with it is that I had to get 12V relays and be very careful to isolate the relay coils with a transistor switch so the load of the actuator switching didn’t jolt the CPU. I found that I could activate the relay and then switch the load with this board, and the power seemed to flow pretty smoothly. Maybe I could ramp up the actuator with PWM on the switch to further improve it? Anyway thing’s working great. Money well spent.
Pretty good... but
So I had a use for this part and I tried it out straightaway. It works as advertised and does a good job, but I wish: 1. That the load connects were screw terminals. The plastic on my terminals shattered on the first use. 2. My Arduino needed 5V not 3.3V so I had to change resistors to get the voltage I needed, although Sparkfun did provide good documentation for me to make that change. Still, I would have liked a simpler way, like a solder pad cut/jumper. 3. Finally I wish that the input and output load solder pads were a little larger. I had molded barrel jack connectors with cables that were slightly too large for the provided pads. I suspect many people will have the same issue.
So good part. Does what it says. Please consider my comments if you make a revision.
Is it just a matter of adjusting R7 and R8 to get a 5V output? any other considerations?
FWIW I am just putting another 47k resistor in parallel with R8 to get the appropriate ratio.
You are correct. Putting a 47K in parallel with R8 will set the output of the buck reg to 5V. Just remember the silk will then be incorrect, and your "3V3" pin will be outputting 5V. And you will want to have your input above 5V (7V or higher will do).
I notice it says max 12v in, but the mosfet and power regulator have a voltage spec much higher. What's the limiting factor on this? Interested on running this from a car battery, which would be in the 14 volt range or so.
There is a capacitor (C4) on the VCC net of this board that is rated for 35V. Usually, it's a good rule of thumb to have capacitors double-rated for whatever your board is planning on using - to survive unwanted accidental spikes. Perhaps we were a bit conservative with our recommend specs on this, as this capacitor voltage rating should still be in the "safe zone" at 1/2 of 35V, so 17.5V.
If you wanted to play it extra safe, you could swap out C4 for a cap with higher voltage rating. Either way, I'd highly recommend doing some sort of testing to verify what your source voltage is looking like. I'm concerned that various cars have various performance in terms of their electrical systems and there could be major spikes in there on startup, RPM changes or sub-system changes.
Curious why the MOSFET is on by default by the gate being pulled up rather than being pulled down?