• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 3 answers
  • Subscribers 65 subscribers
  • Views 668 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

LM5117

LM5117: In my design I am using EPC2020 eGaN as a power switch with LM5117 synchronous buck controller IC . So to drive these GaNFET I want to connect external gate driver LMG1205 to LM5117 synchronous buck controller IC. what is proper way to do this? Act

SUDHANSHU TELRADHE
Intellectual 300 points
Other Parts Discussed in Thread: LMG1205, LMG1210, LM5117, LM5141

  • 0
    TI__Expert 3225 points
    Hello,

    I think you can just connect the PWM output (HO and LO) to the PWM input of LMG1205. Currently we also have an updated part which is LMG1210. It has better performance and delay match. You can take a look as well.

    Thanks and regards,
    Lixing
  • 0
    TI__Genius 12990 points

    Hi Sudhanshu,

    thanks for your question on LMG1205!

    LM5117 has internal high-side and low-side drivers to drive the HO and LO outputs. This requires an external bootstrap. Using LMG1205 is not needed. However you can connect the two due to LMG1205's high impedance 200kohm input resistor that limits the current in this pin. If you want to connect the LMG1205 to the output of LM5117 you can connect HO on LM5117 to HI on LMG1205 (likewise connect LO on LM5117 to LI on LMG1205). LM5117's PGND pin would need to be shared with LMG1205 VSS so a levelshifter is not needed. LI and HI on LMG1205 can go up to 14V. Make sure LMG1205 is close to the EPC2020 to reduce loop inductance. Example layout for LMG1205 can be found in section 10.2 of the LMG1205 datasheet.

    let me know if this answers your question or you have any more questions,

    thanks,

  • 0 in reply to Lixing Fu
    Intellectual 300 points

    Hello Lixing,

    Thank you for suggestion we will go with LMG1210. output voltage of HO pin of LM5117 will be more than input voltage range of LMG1205 HI pin because of bootstrap concept. Thus I did SW pin of LM5117 to ground. Is this proper way? (attached schematic)

  • 0 in reply to Jeffrey Mueller
    Intellectual 300 points
    Hi Jeff,
    Thank you for reply.
    So according to your suggestion I will kept HB pin of LM5117 open(i.e remove bootstrap capacitor) and SW pin of LM5117 I will connect as per application diagram given in datasheet of LM5117. Is this proper way?
  • 0 in reply to SUDHANSHU TELRADHE
    TI__Genius 12990 points

    Hi Sudhanshu,

    You can remove the bootstrap on LM5117 however you will need a supply for the high-side driver. You can connect VCC to HB for this supply and SW would be connected to VSS like you said. Does this make sense?

    Thanks,

  • 0 in reply to SUDHANSHU TELRADHE
    TI__Guru 73752 points
    Hi Sudhanshu,

    You can also consider the LM5141 current-mode controller as it has a 5V gate drive amplitude that's more suited to EPC GaN FETs. Use a switching diode instead of a Schottky for the boot diode to reduce the possibility of the boot rail overcharging due to negative SW voltage.

    Grounding SW of the LM5117 has the disadvantage that adaptive gate drive timing is impaired and also zero-cross current detection for pre-bias startup and diode emulation mode.

    Regards,
    Tim