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UCC27211A: Maximum Duty Cycle

Jonathan Navor
Expert 7845 points
Part Number: UCC27211A
Other Parts Discussed in Thread: PMP21529, , UCC25800, PMP

Hi Team,

Good day! We need your help.

Kindy find below the customer problem and please advise.Thank you very much for your support

I had a look at the PMP21529 Test Report: 4-Switch Buck-Boost Bi-directional DC-DC Converter Reference Design.

https://www.ti.com/lit/ug/tidt046/tidt046.pdf

There you use the UCC27211A as a FET driver. For some cases in this report, the driver has to work at 100% duty cycle for the high side FET.

However, when I look into the datasheet of the UCC27211A I do not find anything regarding the maximum duty cycle of the half-bridge driver.

So my question is: which of your gate drivers support 100% duty cycle and what are their maximum switching frequencies?

I would need a half-bridge FET driver that allows 100% duty cycle and 500kHz switching frequency. If you could supply me with some part numbers that are available as well that would be great

 Could you provide the schematic used in the previously mentioned PMP21529 Test Report? Also, how do I find out the maximal switching frequency your half bridge gate drivers are capable of?
I'll happily come back if any more questions pop up. Thank you in advance for the support. 

Best regards,

Jonathan

  • 0
    TI__Mastermind 20950 points

    Hello Jonathan,

    For the driver operation itself, there is usually not any specific parameter that prevents the driver operating in a DC condition, or 100% duty cycle. There is however with a half bridge driver on the floating high side driver a major consideration on how the high side bias is generated. For most switching converters, a boot diode and bootstrap capacitor is used which operates by charging the bootstrap capacitor when the switch node switches to ground. This results in the bootstrap bias method not being capable of 100% duty cycle.

    To allow DC operation of the high side FET, as the 4 switch buck-boost requires (in theory) a dedicated floating high side bias is required. TI makes simple, small devices for this purpose, one of which is the UCC25800 and another is the SN650x family. This floating bias will allow half bridge drivers to operate the high side in a DC conditions.

    Regarding the switching frequency capability, this is usually not in the parameter table since there are a number of application level considerations, such as total gate drive losses (thermal) and minimum pulse requirements. In the UCC27211A datasheet in the typical curves (Figure 3) you can see that the driver was validation at a condition of at least 1 MHz. Most drivers will have curve data that shows operation at high frequency. The driver is likely capable of operating frequencies beyond what is shown in the curve, but you at least know there was thorough testing at the conditions shown in the curves.

    The schematic for the PMP design is on TI.com at the link below.

    PMP21529 reference design | TI.com

    Regards,