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Project Notes

#570 MT3608 on a Breadboard

A quick breadboard test of the canonical MT3608 switch mode power supply boost converter circuit.

Build

Here’s a quick demo..

clip

Notes

The MT3608 (parts also produced as the B6286) is a very efficient boost converter that can deliver up to 24V at 4A. It requires only 6 external passive components, and is readily available as a complete module for as little as $0.40.

In this project, I’m simply building the standard variable converter circuit on a breadboard to verify its performance.

MT3608

  • 2V to 24V Input Voltage
  • 1.2MHz Fixed Switching Frequency
  • Internal 4A Switch Current Limit
  • Internal Compensation
  • Up to 28V Output Voltage
  • Automatic Pulse Frequency Modulation Mode at Light Loads
  • up to 97% Efficiency

MT3608_functional

Circuit Layout

The M3608 comes in a miniscule SOT23-6 package (0.95mm pin spacing). I’ve put it on a SOT23-10 DIP adapter board for use on a breadboard.

Supporting Component Selection

Inductor

The datasheet recommends a 4.7µH to 22µH inductor with low core loss at 1.2MHz. I’m using a 22µH CDRH104R SMD power inductor.

Filter Capacitors

22µF input and output ceramic capacitors are recommended. I’m using SMD 22µF ceramics mounted on a DIP adapter board.

Diode Selection

A low forward-voltage schottky diode is recommended. I’m using 1N5819 SMD mounted on a DIP adapter board.

Feedback Resistors

The feedback voltage-divider with two resistors establishes the output voltage level where Vref is 0.6V:

Vout = Vref * (1 + R1/R2)

I’m using R1 = 100kΩ variable resistor (“rheostat” wiring), and R2 = 2.2kΩ.

This give a theoretical maximum output voltage of 27.9V.

The theoretical minimum output voltage is 0.6V however in practice the lowest output voltage is limited to around 1 diode drop less than the input voltage, hence there is a bit of dead zone at the lower adjustment.

Note: some boards/schematics will wire the R1 variable resistor in a potentiometer configuration, with the wiper connected to the FB pin. The same principle applies, however the voltage divider calculations of course change.

WARNING: this configuration is only really safe if the input voltage is below about 7V, since otherwise it is possible to push the FB pin beyond the rated 6V when R1 is turned to the extreme. See LEAP#642 MT3608 Safe Control for an alternative that is safe for higher input voltages.

Enable Pin Connection

I’ve chosen not to use this in this build, so it is pulled high to the input power rail (always enabled).

Construction

Breadboard

Schematic

Testing on a breadboard with 5V input and a panel meter to display the boosted output:

Breadboard Build

Credits and References

About
Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.