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LMG3410-HB-EVM: LMG341* Daughter Boards and Motherboards

Sam Ref
Expert 1610 points
Part Number: LMG3410-HB-EVM
Other Parts Discussed in Thread: LMG3410R070, LMG3410R050, DRV421, INA253EVM

Hello

LMG3410R050 and LMG3410R070 have different resistances and hence, I guess, allow different currents.  My questions are;

·        The daughter boards of these Power switches both have a rating of 8Amp. In that case what is the difference between the two daughter boards? Response time of the power switch? If not what is the difference?

·        Is the 8Amp limit arises from the daughter board or the inductors of the mother board?

·        If it is motherboard limitation and we do not use this mother board what is the current limit of each of these 2 daughter boards then?

·        It is said that the motherboard measures the GaN switching....please explain to us what does measuring switching mean? Is it measuring the time of the switching, the voltage during switching, the current during switching ....etc ?

·        The motherboard does not seem to be useful if we want to test closed-loop performance of the daughter board......do you have a product or reference design that we can use if want to test closed loop performance?

·        If we want to use the daughter boards alone....do you have any product or reference design to measure the currents and/or the voltages (AC side and/or DC side of the leg)?

Regards

Sam

 

  • 0
    TI__Expert 3225 points

    Hello Sam, 

    Thanks for asking. Here are my answers:

    1. The devices are rated higher than that, typically at 12A. The limitation regarding 8A is because of the connection pins on the daughterboard PCB. They are rated at 8A and we have to rated it at 8A in this case.

    2. It is not motherboard limitation.

    3. The "measuring switching" means we have switching node test point on the motherboard that you can easily probe on. You can look into the switching node voltage waveform on the motherboard.

    4. Currently we have a lot of reference design with close loop operation, such as PFC, inverter, and DC/DC converters. Please look into ti.com/gan. For this daughterboard and motherboard design, they are mainly for switching performance evaluation so we do not have a close loop function on it.

    5. Most of our reference designs use the daughtercard that we have here. For sure you can purchase the daughtercard alone online.

    Thanks and regards,

    Lixing

  • 0 in reply to Lixing Fu
    Expert 1610 points

    Dear Lixing

    Thanks for your respone.

    Can you please give us a specific design reference or a specific product that we can purchase to measure DC/AC currents and voltages of the abovementioned daughter board. Will appreciate it if you are specific.

    Regards

    Sam Refaat

  • 0 in reply to Sam Ref
    TI__Expert 3225 points

    Dear Sam,

    Please see below for the specific evaluation module (EVM) that you can purchase.

    http://www.ti.com/tool/LMG3410-HB-EVM

    http://www.ti.com/tool/lmg34xx-bb-evm

    We do have a lot more reference designs online with design info and test result available for your reference. 

    http://www.ti.com/power-management/gallium-nitride/reference-designs.html#search?famid=3321

    Please let me know if there is anything that I can help!

    Thanks and regards,

    Lixing

  • 0 in reply to Lixing Fu
    Expert 1610 points

    Dear Lixing

    Thank you for your reply.

    Unfortunately, your response does not address our question. We are not asking about LMG EVMs.

    Kindly look again at our question.

    Regards

    Sam

  • 0 in reply to Sam Ref
    TI__Genius 13641 points
    Hello Sam,

    Thanks for clarifying.

    We do not have a reference design for measuring the current.

    All the test equipment we use are listed in section 3.1 of the user guide: www.ti.com/.../snou140a.pdf

    For the scope probe we typically use 1GHz Passive Voltage Probe – Tektronix TPP1000.

    Hope that helps.

    Thanks!
  • 0 in reply to Masoud Beheshti61
    Expert 1610 points

    Dear Masoud & Lixing

    Thanks for your responses.

    Our purpose of measuring current and voltage is using them in real-time for control system....not for off-line proving/testing.

    We understand that we should be able to extract circuits from a number of TI reference designs that measure current and/or voltage.

    However, we were hoping to find a specific reference design or specific product that is specifically optimized to measure current/voltage for that specific daughter board. It only makes sense that this measurement reference design (or product) exists as that daughter board must have been tested in a closed loop.

    Regards

    Sam

  • 0 in reply to Sam Ref
    Expert 1610 points
    Dear Lixing & Masoud
    We found two EVMs that we think can help us testing these daughter boards (LMG3411-18) in closed loop. These are;
    • DRV421 EVM allow us measure the current of the Daughter board and hence create a closed current loop current. If we are correct about this EVM we would need 3 of these modules....correct?
    • INA253EVM.

    Please let us know if you think if these are appropriate choices.

    Regards
    Sam
  • 0 in reply to Sam Ref
    TI__Intellectual 805 points
    Hi Sam,
    Yes, any current sensor would work for closed loop control but what matters is the measurement location such as floating node or negative rail return, as well as bandwidth required.
    - DRV421 is a magnetic flux sensor which provides isolation, therefore you could measure switch node voltage or high bus voltage with this sensor.
    - INA253EVM can be used to measure low side GAN's current or negative rail current as it is basically sensing the voltage across an internal shunt resistance .
    If you will do a average current mode control with lower bandwidth, I would suggest you to look into reference designs which are using Hall-effect current sensors such as
    www.ti.com/.../PMP20873
    www.ti.com/.../TIDM-1007
    These are closed loop AC/DC power factor correction converters. The design files and schematics are available in the links above.
    Hope this answers your question.
    Regards,
    Serkan