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LMG1205: Question for the number of MOS could be drived.

qianru shi
Prodigy 30 points
Part Number: LMG1205

Hi teams,

When I use this driver, I wonder how to evaluate its driving ability? If I use three MOS in parallel (low-side gate), whether LMG1205 have enough power to drive them?

  • +1
    TI__Intellectual 2100 points

    Hi Qianru,

    Thank you for reaching out! I'm going to link to another E2E post that helps evaluate the minimum drive current needed for an application: Link to post.

    This calculator tool will allow you to input the circuit information to determine the minimum drive current needed for your application. Since you plan on driving 3 MOS in parallel, you would input 3 for the # of FETs driven by one output.

    Please feel free to reach out if you have any questions over the tool or any other questions over LMG1205!

    Best,

    Alex Weaver

  • 0 in reply to Alex Weaver
    Prodigy 30 points

    Hi Alex,

    Thanks for your reply!

    When I use this calculator tool, I found the rise time in the datasheet of LMG1205 is shown in this table:

    I chose 7ns and the result is around 13A, is that satisified the design requirement of LMG1205? (I think the current limit is 10A or others?).

    Looking forward to your reply, thanks a lot!

    Best,

    Qianru

  • 0 in reply to qianru shi
    TI__Intellectual 2100 points

    Hi Qianru,

    No problem! Could you share the switching frequency that you are expecting for this application? Also, is the 7ns rise and fall time needed?

    6A is actually the max current rating supported by our half-bridge gate driver portfolio. LMG1205 is rated for 1.2A/5A source/sink current capability. Depending on the switching frequency, you may be able to extend the rise/fall time which will reduce the current requirements. Choosing low Qg FETs will also help minimize the drive current. Lastly, if the fast rise/fall time is needed and the FETs cannot be changed, you will likely need to reduce the number of switches being driven by each output of the driver.

    Please help confirm the switching frequency of the application and let me know if there's any other questions I can help answer!

    Best,

    Alex Weaver

  • 0 in reply to Alex Weaver
    Prodigy 30 points

    Hi Alex,

    The swithing frequency is around 1MHz. I chose 7ns cause the datasheet of LMG1205 shows, is that could be changed? (How?)

    The Qg of FETs is around 30nC with Vgs=5.5V, which is higher than 1.2A: 

    If I write the correct parameters in this table, LMG1205 will not be able to use. Is there any other Driver with the same size could be suggested?

    Thanks,

    Qianru

  • 0 in reply to qianru shi
    TI__Intellectual 2100 points

    Hi Qianru,

    It looks like the closest fit for this project in a similar sized package is TPS51604. This half-bridge driver has a 2mm x 2mm sized package (compared to 1.8mm x 1.8mm) and looks like it can support currents well above the needed threshold:

    One parameter to consider is the extended rise time of 30ns (typ). We have other drivers with shorter rise/fall times and higher drive strength capability such as UCC27211A, but these drivers will have larger sized packages.

    Please let me know if you are still unsure which device would be best, or if there's any other clarifying information I can help provide.

    Best,

    Alex Weaver

  • 0 in reply to Alex Weaver
    Prodigy 30 points

    Hi Alex,

    Thanks a lot for your suggestion, it's very useful !

    Best wishes,

    Qianru