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LM5170: Disable diode emulation mode

Koji Ikeda
Expert 6295 points
Part Number: LM5170

Hello support team,

Can LM5170 disable diode emulation mode? If yes, please explain how to disable it.

Thanks,

Koji Ikeda

  • 0
    TI__Guru* 78080 points

    Hello Ikeda-san,

    The LM5170's diode emulation is always activated.  In order to disable it, you need to introduce a dc bias signal to the current sense. Could you tell which mode do  you need to "disable" the DEM,  in buck, or boost, or both? 

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    TI__Expert 6295 points

    Yuohao-san,

    Thank you for your support.

    Customer has concern in load transient at Buck CV mode. If diode emulation might have pulse skipping at very light load, this might cause poor load response. Do you have any way to improve it?

    Thanks,

    Koji Ikeda

  • +1 in reply to Koji Ikeda
    TI__Guru* 78080 points

    Hi Ikeda-san,

    Yes there is a way to work around.  That is to introduce a offset voltage to the current sense signal.   A simple way is to place a few kOhm resistor from CSB pin to GND, which forms a resistor divider with the CSB pin series resistor (1~2 Ohm) and introduces a dc bias by slightly pulling down the CSB pin voltage. 

    Hope this clarifies.

    Thanks,

    Youhao