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Original question:

UCC28730-Q1: Input voltage range

UCC28C41-Q1: Differences in UCC28C4X_ duty cycle and UVLO

Scarlett Cao
Expert 3360 points
Part Number: UCC28C41-Q1
Other Parts Discussed in Thread: UCC28C40-Q1, UCC28C41

Hi team,

I'd like to check my understanding about the difference between UCC28C41-Q1 and UCC28C40-Q1. UCC28C41-Q1 can only be operated with input from LV(12V battery as an example), while UCC28C40-Q1 works for HV application as well with a start-up circuit, is that right? Can you help me understand why 100% duty cycle is necessary for HV input? 

I've read  slyy164 UCC28C4X selection guide for automotive isolated DCDC auxiliary power application but not fully understand. Could you please explained more on the applications limitation of different UVLO combinations?

Thanks,

Scarlett

  • 0
    TI__Expert 7080 points

    Hi Cao,

    Both of UCC28C41 and 28C40 can support HV input applications.

    For duty cycle limitation . It only related to input voltage range , for narrow range input , the 50% max. duty cycle can meet output regulation and it can brings some benefits, such as no need slope compensation and reducing the risk of saturation of transformer . but for wide range input . 100% max. duty cycle is required.

    For UVLO , it only depends on how to power VDD , for example , 14.5V/9.0V UVLO means the controller will start operate only when VDD voltage up to 14.5V and will turn off at 9.0V . so for a 12V input application . you can't turn on the controller without a additional start up circuits. but for 8.4/7.6V system . 12V input is ok to power on the VDD.  In short. UVLO only related to how to power on/off the controller.

    Hope can answer your questions.