• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 387 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM76003-Q1: 9-36V input, 12V output, when the input is lower than 12V, how does the device work?

Sherry Liang
Genius 10255 points
Part Number: LM76003-Q1

Dear team,

The input voltage is 9V-36V, and the nominal voltage is 24V. The expected output is 12V. When the input is lower than 12V, in my understanding the high side mosfet will be always on, right? At this time, the duty cycle will keep the largest value, and the output is a little smaller than the input, right? Is there any risk when doing this?

Thanks & Best Regards,

Sherry

  • 0
    TI__Expert 6245 points

    Hello Sherry,

    Yes, when input falls below the output’s setting, duty factor goes to its maximum value and frequency drops to allow this maximum duty factor to be very high. All safety features remain active and the part will resume normal regulation once input rises. There are two things to consider when operating the part in this mode:

    1. Since duty factor is at its maximum value, load transient performance is poor – it is as though there were no chip, just an inductor.

    2. If input voltage rises suddenly, the output will follow unless this rise is fast enough to operate the part in current limit. Since there is a large current present while output voltage is rising, there is overshoot once the parts starts regulating. This transient will look like a load step from near current limit to what ever DC load is on the output.

    Regards, Robert