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Original question:

LM5170-Q1: LM5170-Q1: External gate driver(UCC27712DR)

UCC27712: Need high-side gate driver to provide short pulse, around 25-40 nanoseconds

Mitchel Szazynski
Prodigy 30 points
Part Number: UCC27712
Other Parts Discussed in Thread: UCC21520

Hello, I have identified the UCC27712 as a component which could satisfy my needs for a high-side driver, but wanted to confirm that I correctly interpret its specs.

I am using it to drive the SPW11N60C3 MOSFET, which has 300V coming from the power rail.

https://www.digikey.com/en/products/detail/rochester-electronics-llc/SPW11N60C3/12131755

I am not concerned about propagation delays in the system, but the critical factor is that I want fairly precise control over the actual "On-time" of the switch, which should be in the 25-40 nanosecond range.

The datasheet seems to indicate "minimum ON pulse that changes output state" that 25 nanoseconds is *normally* enough, with worst case being 45 nanoseconds. I don't know how likely or how often this "worst case" is to occur...but I wanted to just confirm that this would be an appropriate IC for my application?

  • 0
    TI__Guru**** 189401 points

    Hi, Mitchell,

    My colleague who supports this product is currently out of the office. He will return next week and will respond at that time. 

    Thank you for your patience. 

    Best regards,

    Don

  • 0 in reply to Don Dapkus
    Prodigy 30 points

    Any update on this?

  • 0 in reply to Mitchel Szazynski
    TI__Mastermind 23215 points

    Hello Mitchel,

    For the minimum input pulse width, I recommend working within the maximum spec of 45ns to accommodate part to part and temperature variance. 

    Can you comment on why the high side on time of 25-45ns is critical? Is this a minimum duty cycle target or some other operating condition?

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 30 points

    This is for an ultrasound pulser-receiver application, and shorter pulse widths will provide higher frequency response bandwidth. This may be good enough, but out of curiosity, is there a different chip you would recommend that could do smaller pulse widths? I had one lined up that would work up to several hundred volts, with pulse widths as low as perhaps 10 nanoseconds, but then I realized it was only a low-side driver. I've struggled to find a high-side driver with the right specs

  • 0 in reply to Mitchel Szazynski
    TI__Mastermind 23215 points

    Hello Mitchel,

    The requirement you have of a 300V bus makes it necessary to have a driver with a rating adequate to meet this which will put you in the 600V half bridge driver devices. There are 120V half bridge drivers with much better narrow pulse response but this would limit you to 100V or less high voltage inputs.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 30 points

    So the UCC277 is the best option for this voltage? And for clarity, it sounds like you think it's possible that this will work with a pulse shorter than 45 ns, but with the various tolerances in the part, it's difficult to be totally sure for anything <45 ns?

  • 0 in reply to Mitchel Szazynski
    TI__Mastermind 23215 points

    Hello Mitchel,

    A co worker reminded me that the TI isolated drivers can meet your voltage requirement and have good narrow pulse response. But the cost will be higher than the UCC27712. The UCC21520 is a device you should consider as I think it meets the pulse response and voltage requirements.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 30 points

    I appreciate the info. One (probably) final question: As I study the datasheet, I see that the output requires both a positive and a negative power supply which is distinct from the input power supply. I can't tell if these supplies on the output side need to be isolated supplies; If so, where should the ground be connected for each? There will be a +VDDB and a -VSSB, each of which must be referenced to its own ground. Can the ground to which +VDDB and -VSSB is referenced be connected to the input side ground? If not, where?

  • 0 in reply to Mitchel Szazynski
    TI__Mastermind 23215 points

    Hello Mitchel,

    I assume with your references to VDDB and VSSB you are looking at the isolated driver that was suggested.

    The isolated drivers are configured to allow for maximum flexibility for both output channels. If you want to operate, as a UCC27712 driver with the low side referenced to ground, you can tie VSSB to ground, and share the VDDB with VCCI if the bias is within the 18V rating of VCCI (control bias). 

    The other VDDA can be generated with a bootstrap supply if the switching allows for the switch node to switch to ground which allows the boot cap to charge. If not you would need an isolated bias for the floating high side drive.

    Regards,