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LM2696EVAL: Powering Raspberry Pi

Pol Francesch
Prodigy 40 points

Part Number: LM2696EVAL

Hello,

I recently asked a question about a different buck converter to power my raspberry pi, however I have realized that the maximum input current for the Raspberry Pi is 2.5A(I doubt it will use this much but just in case), and the buck converter I was previously looking at can only function up to 1.5A.

Hence I was wanting to use the LM2696EVAL board to power a Raspberry Pi at 5V and optimally 1.5A but at a maximum 2.5A, using a 12VDC power supply. First and foremost I want to make sure that this board can handle this. Secondly I would like to know how I could go about adjusting the Vout of this board so it is 5V.

Thank you very much in advance,

Pol.

  • 0
    TI__Prodigy 580 points

    Hi Pol,

    These are fairly common questions that an engineer runs into quite often. To help out more, I will take a minute to go ahead and give you a quick insight into the best ways to find these answers in the future.  The "Technical Documents" page for the part will have all of your needs: http://www.ti.com/product/LM2696/technicaldocuments 

    1) The first place to start is always the Data Sheet. The specifications at the top of the data sheet show that your needs will be met by this converter. 

    (The full spec table that is lower in the data sheet can provide you more info if you need to look for any other ratings)

    2) The next step, since you are using the EVM, is to look at the User Guide. This is where you will find the EVM schematic. 

    If you were not using the EVM, the "Applications Section" of the data sheet would be the next spot to look. 

    A resistor divider is used on the output to set Vout. In this case, RFB1 and RFB2.

    3) The next step is to find the equations from the Data Sheet or User Guide for the resistor divider.

    4) Last, changing the resistors will be the same process as the other board. But be sure to check the BOM in the User Guide to ensure you get the right size footprint for the resistors.In this case it is 0805.

    Thanks,

    Alec Heierman

    TI Applications Engineer

  • 0 in reply to Alec_Heierman
    Prodigy 40 points
    Hello Alec,
    Thank you very much for that reply. I simply wanted to double check so that I do not purchase the incorrect parts as I have had a tendency to do this in the past.
    Would it be fair to use the 1.255V as the internal reference voltage? I know it mentions that this is typical, but I'm not certain what "typical" actually refers to.
    Thank you again,
    Pol.
  • 0 in reply to Pol Francesch
    TI__Prodigy 580 points
    "Typical" refers to the fact that the actual value will fall in a range. The range can be found in the "Electrical Characteristics" table in the Data Sheet. For your use, using the typical value is the best way to calculate the resistor values.

    Thanks,
    Alec Heierman
    TI Applications Engineer