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Automatic Power Path management based on fixed input priority

Marius Jansen van Rensburg
Prodigy 210 points

Hi,

I am currently designing an MCU breakout board / development board.

The MCU requires a 3.3V supply, but I would like a 5V rail available on the board to interface with 5V compatible devices.

I am looking for a solution that will automatically select one of three power-paths/supplies to the board, based on a fixed priority:

  1. 5V - 28V DC input (which will be converted to a 3.3V and 5V output) - should be able to supply up to 3A of current (will probably use the "TPS54331" x2 for this) - this is priority one, so this input should be selected even when the other two are present;
  2. A normal USB connection (5V, 500mA max) - will probably use an LDO to switch to 3V and drive the 5V rail directly from the USB supply;
  3. A supply that will be provided by an In Circuit Serial Debugger (3.3V, < 500mA) - 5V rail will not be powered when this is the only supply available.

I'm not expecting a complete design here, but a reference to a single chip power path controller (not a battery charging circuit) or an application note on automatic power path management will be appreciated.

  • 0
    TI__Genius 15780 points

    Hi Marius,

    I have moved your post to the power interface forum.

    Regards,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    TI__Mastermind 42795 points
    As a start, please have a look at TPS211x auto-switching pwr mux family. You may have to gang a couple of them together for 3 rails.
  • 0 in reply to Eric Wright
    Prodigy 210 points
    Hi Aleksandras,

    Thanks for your reply. This would be a good solution, but the input voltage range is too small. Another concern is the maximum current (2A max if I understand the datasheet correctly).
    Since my post, I found a product (not manufactured by TI) that can accomplish exactly what I need. The LTC4417 can manage three inputs and have a wide Vin. It does however require an almost ludicrous amount of external components (at least 19 on a quick first count) and is quite expensive (compared to the TPS211x range). This design was never intended for mass production so I am not too concerned about the price. I can probably cascade a few MOSFET circuits to accomplish the same thing (currently looking into this).