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LM5175: LM5175 schematic review

Dexter Choi
Expert 2795 points
Part Number: LM5175
Other Parts Discussed in Thread: LM5176

Dear Sir,

could you help review our schematic for attached file.

please let me know that your advisement.

please refer below spec.

Input : DC12V ~ 30Vdc

Output: 14.6Vdc, 20A(max)

 Drive by Charger_Circuit.pdf

  • 0
    TI__Mastermind 21720 points

    Hello Dexter,

    Thanks for reaching out with you question and using TI products. For this application I suggest using the LM5176. This is the newer generation of the LM5175 and will work in this application better. The devices are pin to pin compatible the RT pin resistor will need to change to match the LM5176 datasheet.

    Can you please provide the saturation current of the inductor?

    Please take a look at the reference design below that uses the LM5176

    Garrett

  • 0 in reply to Garrett Roecker
    Expert 2795 points

    Dear Garrett,

    Unfortunately design is fixed so we can change LM5176.

    saturation current is 43A.

    please refer to below datasheet of the inductor.

    SRP2313AA_ind.pdf

  • 0 in reply to Dexter Choi
    TI__Mastermind 21720 points

    Hi Dexter,

    The LM5175 quick-start calculator can be used to double check the values of the design.

    http://www.ti.com/tool/lm5175quickstart-calc

    The one thing I notice is the inductor has a saturation current of 42A. When the current sense resistor is 2mOhm the limited peak current is going to be 80A. I suggest selecting an inductor with a higher saturation current of switching to the LM5176 which has a lower peak current limit boost mode than the LM5175.

    Since the output current is high for this design I suggest adding a place holder for another MOSFET on the high-side boost MOSFET.  This will help with conduction losses.

    It looks like you are using this in a charging application. I suggest keeping the LM5175 out of hiccup current limit mode by changing the MODE pin to be tied to VCC. This will disable hiccup current limit protection.

    Please let me know if you have any questions.

    Thanks

    Garrett