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TPS28226: Have a question if TPS28226 can achieve 90% duty cycle at 100kHz

Charles McCallum
Intellectual 2620 points
Part Number: TPS28226
Other Parts Discussed in Thread: SN6501

Can this part achieve a 90% duty cycle at 100kHz?

  • 0
    TI__Genius 12990 points
    Hi Charles,

    Thanks for reaching out about TPS28226. I have reached out to the appropriate engineer with this device to answer your questions asap.
    Can you tell me what FET your using?

    thanks,
  • 0 in reply to Jeffrey Mueller
    TI__Genius 13445 points

    Hi Charles,

    My name is Mamadou Diallo, I am an applications engineer and I will help address your inquiry.

    To clarify, do you mean 95% duty cycle on the upper FET?

    TPS28226 uses a bootstrap capacitor between BOOT pin and Phase pin to provide bias to the upper gate. This boot cap is initially pre-charged during the first ON-time of the upper FET(while lower FET is OFF). When the lower FET turns ON, the boot cap uses this time interval to replenish (through low impedance path to ground) in order to provide bias again for the upper FET on the next cycle. As you may imagine, this operation is limited by duty therefore too high duty cycle on the upper FET will cause the boot cap to run out of charge leading to the upper gate voltage falling below threshold and turn-off the upper FET. On the other hand, too long time ON time of lower FET will overcharge the boot cap.

    For high duty cycle, a common work around is to use the driver with SN6501(commerical grade if not automotive) (www.ti.com/.../sn6501.pdf) as shown on the block diagram below.

    What application and End Equipment is this for? 

    Please let us know if you further questions or press the button if this helped address your inquiry.

    Thanks.

    Regards,

    -Mamadou