• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 77 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LM53625-Q1: SYNC input- conflicting DS entries

Mark Pieper
Expert 4430 points
Part Number: LM53625-Q1

Hi,

There is an apparent contradiction in the DS. Can you clarify which of these is correct?

8.3.6: The device remains in FPWM mode and operates in CCM for light loads when synchronization input is provided.

8.4.1: The SYNC input is ignored during PFM operation.

Thanks,

Mark

  • 0
    TI__Genius 10655 points

    Hi Mark,

    There is no contradiction here, both statements are correct.

    FPWM stands for Forced Pulse Width Modulation meaning the part will regulate the output by switching at a fixed frequency and varying the duty cycle or pulse width.

    PFM stands for Pulse Frequency Modulation where the part regulates the output by switching at a constant on-time and varying the frequency. 

    Regards,

    Harrison Overturf

  • 0 in reply to Harrison Overturf
    TI__Expert 4430 points

    Hi,

    The contradiction is that if the sync signal causes the device to stay in FPWM mode down to light load, the device will never enter into PFM mode. If the device enters into PFM mode and the sync signal is ignored, then it is not staying in FPWM mode down to light load. These two descriptions are contradictory.

    - Mark

  • +1 in reply to Mark Pieper
    TI__Expert 4430 points

    I've verified that the DS 8.4.1 third paragraph last sentence is incorrect and should be removed. As stated in 8.3.6: "The device remains in FPWM mode and operates in CCM for light loads when synchronization input is provided." Therefore, when a SYNC clock is applied, the device never enters into PFM mode and stays in FPWM mode down to very light load. Also note that per 8.4.3, when VIN falls and the device is operating in dropout mode the sync signal is ignored.