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LM5148: Higher Current Capacity Battery Charging: LM5148 Design Modification

Amish Shirsat
Prodigy 30 points
Part Number: LM5148
Other Parts Discussed in Thread: LM5149, LM5116, PMP7282, PMP, LMG5200

Hi there!

For an input voltage range of 36–60V and an output value of 14V, 70A, I am designing a DC converter (Synchronous Buck). Operation of CCCV is necessary because it is used for battery charging. The LM5148 & LN5149 IC is what I found because there isn't a specific ASIC for this requirement. Therefore, I would like to change the design to meet my needs. Please let me know.


1) Is there CCCV support for LM5148/LM5149?

2) Considering its lower current capacity, is it possible to synchronize two ICs (converters) for dual phase operation, similar to what PMP7282 for LM5116 does?

3) In an effort to enhance the design, we were considering using GAN FETs. Can we and how can we do this?

4) In terms of size, thermal capacity, and current, what would the benefits of employing GAN be?

Thank You.

  • 0
    TI__Mastermind 40060 points

    Hello Amish,

    Please refer to the application note in link below.

    How to Design a Simple Constant Current/Constant Voltage Buck Converter (ti.com)

    Figure 1 shows a basic circuit you can use and implement with a controller implementation.

    seeing as the circuit in Fig 1 connects to the Feedback, using this in conjunction with the PMP complicates things.  Easier to use the LM5148/9 as this simply ties the COMP pins together.

    You can use GAN, but if the nominal voltage is 48V will need to look at the benefits GAN provide at this input voltage, results could be similar to Standard MOSFETs, unless you wish to switch at higher frequencies...  We have the LMG devices that can be used with our controllers.  Please refer to the EVM user guide of the LMG5200 for more details of how to configure the GAN devices.

    Using the LMG5200EVM-02 GaN Half-Bridge Power Stage EVM (ti.com)

    Hope this helps.

    David.

      

  • 0 in reply to David Baba
    Prodigy 30 points

    Hi, David I am grateful for your reply.

    1) The fact that the LM5148/49 lacks an inbuilt CC mode and so needs additional circuits clarifies any confusion regarding CC functioning.

    2)But since my second query remains unaddressed, will you kindly address my uncertainty about dual phase synchronization for increased current capacity?

    3) Since the maximum current in the LM5148/49 is said to be 20A, is it possible to increase current capacity by utilizing GAN since the current restriction is caused by the gate  sink/source current of the IC?

    4) Is there any way you could increase the converter's current capacity?

  • 0 in reply to Amish Shirsat
    TI__Mastermind 40060 points

    Hello Amish,

    Yes, making multiple phases increases current capability, as it minimizes the practical design for given current per phase and also in effect, distributes the heat across more MOSFETs.

    At the given input voltage levels, switching to GAN will not get you significantly more current capability to the extent of reducing the required number of phases, the differences are minimal.

    Yes, you can increase current capacity by increasing the number of phases and decreasing the current per phase.

    Hope this helps.

    David.