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Super Boost 3.6A USB charger based on LM2700

Posted on Friday, April 27th, 2012 in open source, project logs by DP

Scrawny 500mA USB charger insufficient for your hunger for power? Try this 3.6 amp USB charger based on the LM2700 boost switch-mode IC.

This design is inspired by the Minty Boost but it fixes some of the issues that I had with it. The Minty Boost is limited to 600mA due to the LT1302 chip. The Super Boost uses the LM2700 which can push up to 3.6A. This will enable i-devices to draw up to there maximum of 1A which will enable a faster recharge.

This project is open source hardware, and all the design files are available.

This entry was posted on Friday, April 27th, 2012 at 7:00 pm and is filed under open source, project logs. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

18 Responses to “Super Boost 3.6A USB charger based on LM2700”

  1. JBeale says:

    Note that “3.6 A” is the maximum rating of the internal switch in the IC, and not the available output current at 5V. That would be lower due to the step-up voltage factor, and the fact that the circuit does not operate with 100% duty cycle.

  2. German says:

    Maybe this little baby will be my brand new (Shipping in August!) Raspberry Pi power source…. :) Yummy Yummy!!!… I wonder if it will work well…

  3. erdabyz says:

    Interesting project, but I’m afraid to say that this is not a very good board layout for such a regulator. It uses way too thin and long traces (even if they do look thick and short, the truth is that there shoudn’t even be traces in the power part of this design, but filled polygons straight to the pads of the components). Also the feedback path is unnecesarily long and runs in paralel and pretty close to the output voltage trace. The feedback path should be no more than 5mm long in the very worst case.

    For example, if you rotate the LM2700 90 degrees to the left then you’ll have a direct path to connect the coil, the caps and all the feedback stuff with ultra wide and short copper polygons. And you wouldn’t increase the size at all.

    Unfortunately it’s really common to see switch mode power supply layouts with several basic design flaws. Minty boost has a crappy layout, most (if not all) of sparkfun’s SMPS designs are even crappier….

    • Thanks for the help erdabyz! I just pushed out V1.1 with the fixes you mentioned. I also added a small analog ground to help remove the switching noise from the feedback loops.

      http://longhornengineer.com/projects/pcb/super-boost-standalone/

      • erdabyz says:

        Yeah, now it’s much better, congratulations!. There are a few tweaks i’d still try to make.

        For example, the ground path for the 470uF output cap is too long. Maybe you can rotate it 90 degrees to the left and make the Vout trace run below the cap and USB connector (i’m not sure if this coud be done in an elegant way) , so the GND pad of the capacitor would have a direct and short path to the LM2700’s gound pads. Maybe it wold be easier to do this by rotating the cap to 45 degrees or something and having the Vout trace run between the capacitor’s pads.

        Also the feedback path is still too long, and what worries me more is the fact that the “branching” for the feedback resistor occurs after the USB connector. There you have some parasitic inductance after the connector, which is taking the bulk of the current, so small voltage shifts could occur which would affect the feedback performance and induce noise to the whole regulator.
        You should try to place the 3.01 and 1.02k resistors close to where the 4.7nf and 20k resistors are, right next to the output cap’s vout pad, to have the shortest possible feedback path.

        With those improvements, and if possible a bottom ground plane well stitched to the upper one with some vias, the desing would be pro.

  4. voidptr says:

    here my silly question … is it safe to pass more than 2A in an usb connector , i thought the connector was rated for less than that … ? :-)

    • Yup most are rated around 1.5A. Thats why when you plug in a iPhone it will limit to 1A. Now that doesnt stop you from putting leads instead of the USB socket and using it to the full potential ;)

  5. LawrenceSeattle says:

    Cool. I’ve been looking for something like this. Easily etchable too. What devices has this been tested with?

  6. heychris says:

    It would be cool to add in one of the device emulator chips that detect DCP (digital charging port). The same chips usually can detect apple’s divider mode.

    http://www.ti.com/product/tps2543

    • Pretty niffty chip there! Only problem I see is mouser only has 250 of them and its in a lead less package. It is a new chip though according to mouser so they should be getting more. Will look into adding it in the next version.

  7. heychris says:

    I agree.. I’d rather have an easier to solder chip. I’ve also looked at the maxim 16919/16969 and MAX14617. Honestly I’m trying to do the same as you, but am unsure which chip would actually do it.

    I ordered samples of what I could.. I already have samples of the tps2543. I’ve found soldering the QFN first to DIP adapters seems to be pretty easy to do.

    I’d be curious to get your opinion on the maxim chips.

    http://www.maxim-ic.com/datasheet/index.mvp/id/7515
    http://www.maxim-ic.com/datasheet/index.mvp/id/7552

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