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UCC28730-Q1: Switching stop circuit

tateo yamashiro
Guru 10890 points
Part Number: UCC28730-Q1
Other Parts Discussed in Thread: UCC28730, UCC27532-Q1, UCC27531-Q1, UCC27531

Hi,

We got a question from the customer about UCC28730-Q1.
Could you help us?

[Question]
They are considering the switching stop circuit. They need the fast wake-up from stop switching to re-start switching. Therefore they need that not the IC is shutdown but the IC is wake-up and disable the pulse. Is there any recommended solution?
For this requirement, they are considering the pull-down circuit on DRV. Are there any concerns about this usage?

Best Regards,
tateo

  • 0
    TI__Expert 6080 points
    Hello Tateo,

    I see a problem with this application when the DRV is pulled LOW that does not mean that the IC is disabled because DRV will still demand 29mA from VDD and once CVDD is depleted the controller will shut down.
    Have the customer thought about this problem?

    Kind Regards,
    Sonal
  • 0 in reply to Sonal Singh
    Guru 10890 points

    Hi, Sorry for the delayed reply.
    They realized the problem because of your help. Now they want to consider some option. So please let us confirm one thing. If they use the circuit which the DRV is pulled low while the IC is switching, is there any possibility to cause damage to the IC?

    Best Regards,
    tateo

  • 0 in reply to tateo yamashiro
    TI__Expert 6080 points
    Tateo,

    They will not damage the controller if they pull DRV LOW.

    Sonal
  • 0 in reply to Sonal Singh
    Guru 10890 points

    Hi, It has been long time since we last contacted each other.
    They are considering using gate driver which has EN function for ON/OFF control. If they use VDD for Vcc of gate driver, they should consider both the start-up current of IC and gate driver is not over Ihv. Is this my understanding correct? If there are the recommended parts of gate driver, please let me know.

    Best Regards,
    tateo

  • 0 in reply to tateo yamashiro
    TI__Expert 6080 points

    Hello Tateo,

    I do not see any issue with this application. One of the things to see is; the source current of UCC28730 is 35mA and the driver only requires 300uA to startup.

    I would like to point out that the VDD max for UCC28730 is 38V however for the driver is only 35V.

    The other driver that you can have a look at is UCC27532-Q1, this driver has the exact same features but gives you a bit of flexibility over temp.

    I hope this answers your question.

    Regards,

    Sonal

  • 0 in reply to Sonal Singh
    Guru 10890 points

    Hi, Thank you for your reply.
    They are concerned about the startup operation. If the start-up current of gate driver is bigger than Ihv, Ihv can't charge the VDD capacitor. For example, if the Iddoff(300uA max) of UCC27531-Q1 flow through from Ihv, the Ihv(100uA min) can't charge the VDD capacitor. Is this my understanding correct?

    Best Regards,
    tateo

  • 0 in reply to tateo yamashiro
    TI__Expert 6080 points
    Hello Tateo,

    I think there are two possible solutions to this issue:
    1. The solution would be either to disconnect the VDD supply to the UCC27531 during start-up – i.e. a series switch between the UCC28730 -VDD
    and AUX diode connection and the UCC27531-VDD. The tricky part will be controlling this switch.
    2. The other options would be to find a GATE DRIVER with lower current, or to use a simple passive drive boost stage – a simple NPN/PNP is a
    common method and can provide significantly more gate drive.

    Regards,
    Sonal