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LM5085: Question on "Functional Block Diagram"

Shotaro Sakai
Intellectual 2900 points
Part Number: LM5085

Hello team,

Can you tell me the how the red part work?

  1. What is purpose of OFF Time One-Shot?
  2. What is status of the SR flip flop when OC occurs?

Best regards,

Shotaro

  • 0
    TI__Expert 3766 points

    Hi Shotaro,

    The OFF Time One shot block modulates the duration of the off time delay for the PFET once OC is detected by the comparator.

    Depending on VIN, and FB which are inputs into the block, the off-time may vary to allow inductor current to decrease to a low level before the next on-time. 

    In general, when an OC event occurs, the SR latch will output an OFF signal through Q to the gate driver that is modulated by the OFF-time one shot block. See section 7.3.4 in the datasheet below.

    Regards,

    Henry

  • 0 in reply to Henry Kou
    TI__Intellectual 2900 points

    Hi Henry-san,

    Thank you for the reply. I understood the block purpose.

    In addition, do we have min/max value for 1.25V at Soft-Start and 1.6V at REGULATION COMPARTOR?

    Best regards,

    Shotaro Sakai

  • 0 in reply to Shotaro Sakai
    TI__Expert 3766 points

    Hi Shotaro,

    This is a very specific question where I have reached out to the product line. I will get back to you, thanks.

    Regards,

    Henry

  • 0 in reply to Henry Kou
    TI__Expert 3766 points

    Hi Shotaro,

    From the product line, the 1.25 Vref has a max and min as denoted in the datasheet. For the OVP measured with respect to Vref, the range is min 0.325V to max 0.360V with typ value of 0.350V.

    Regards,

    Henry