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[ LMG3410 ] Low Fs Operation and UVLO Behavior

Kenichiro
Mastermind 9165 points

[ LMG3410 ] Low Fs Operation and UVLO Behavior

Hi,

My customer has been studying GaN solution, e.g. LMG3410 for their AC servo motor application. Can you help me to answer some queries from them?

<Q1: Low Fs Operation>:

As my understanding, in general, GaN can offer more benefit on high speed opeartion such as MHz. However, my customer would like to use this with switching frequency as low as 7KHz range. Are there any negative point and/or drawback expected?

<Q2: VDD Supply Current For Low Fs>:

Do you have a graph which express VDD supply current down to few KHz? Fig. 5 in the datasheet show down to 10KHz.
(It's already close to 1mA, quite small, though.)

<Q3: UVLO Behavior>:

According to datasheet, UVLO is triggered with supply voltage lower than 8.6V (min). Do you have any data which show until how much low voltage can LMG3410 maintain its operation correctly?

Thank you for your support in advance.
Regards,
Ken

 

  • 0
    TI__Prodigy 230 points

    Hi, Ken

    Here are the answers for your questions.

    <Q1: Low Fs Operation>:

    There should not be any problem for GaN to work with low switching frequency. But, could you let me know why the custom need GaN for such low switching frequency operation and why Si is not good enough?

    <Q2: VDD Supply Current For Low Fs>:

    We don’t have a graph which expresses VDD supply current down to few kHz currently. But, I can give you the estimation based on our testing results. Without switching, the supply current will be 0.6mA, while the supply current is around 1A with 10 kHz switching frequency. The best estimation for fsw kHz below 10 kHz will be 0.6mA + (1-0.6mA)*fsw kHz/10kHz = 0.6mA + fsw * 0.04mA, e.g. 0.8mA for 5 kHz switching frequency.

    <Q3: UVLO Behavior>:

    Answer: Since the UVLO varies from 8.6V - 9.4V, the minimal VDD supply voltage for normal operation will be 9.5V as it shown on the datasheet.

    Regards,
    Ted

  • 0 in reply to Ted(Runruo) Chen
    Mastermind 9165 points

    Hi Ted,

    Thank you for your reply!

    With regards to Q1, yes, it's still challenge for my customer (for me, too!) whether GaN can gives benefit compare with Si FET. According to customer calculation, their system cannot be supported by Si FET(IPM) from current capability aspect. But it's not understandable for me yet. I'm keep checking and come back to you, once it's clarified.

    Thanks,
    Ken