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LM2611: Condition for Hysteretic mode

Satoshi
Guru 19645 points
Part Number: LM2611

Please let me know about two points below for Hysteretic mode function;

①Condition of enter Hysteretic mode

　For example, inductor ripple current reached 0A, or reached minimum on time, etc.

②Spec for minimum on-time

Best regards,

Satoshi

  • 0
    TI__Expert 7925 points
    Hi Satoshi,

    1. The border for hysteretic mode is not specified. We can measure it, if you give us specific operating conditions.
    2 . There is no minimum duty cycle specified, only the maximum value (around 0.9).

    Best regards,
    Milos
  • 0 in reply to Milos
    Guru 19645 points
    Milos-san

    Thank you for reply,
    Please see operating condition below;
    ・5Vin ⇒ -5Vout / Iout: 175mA
    ・Inductor: 22μH ×2
    ・Cin and Cout: 22μF
    ・Ccuk: 1μF
    ・Cff: 1000pF

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Expert 7925 points
    Hi Satoshi-san,

    Under those conditions (Vin=5 V, Vout=-5 V), the regulator will go into pulse skipping mode for Iout<40 mA, at Iout=175 mA it will operate in regular PWM mode.

    Best regards,
    Milos
  • 0 in reply to Milos
    Guru 19645 points
    Milos-san

    Sorry for my reply delay,
    Please let me confirm about two points below;

    ①Is Iout<40mA mean that inductor current reached 0A?
    　(My calculate was also about 40mA by datasheet equation.)
    ②Is Hysteretic mode the same as pulse skipping mode?

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Expert 7925 points
    Hi Satoshi-san,

    1. Yes, the device transitions into pulse-skipping mode (instead of discontinuous conduction mode) when the inductor current reaches zero.
    2. In this case, yes. In general, hysteretic mode is not the same as pulse-skipping mode. Here, hysteretic mode means that the output voltage bounces between two set values, and the way it does that is by using pulse-skipping.

    Best regards,
    Milos
  • 0 in reply to Milos
    TI__Mastermind 20900 points

    Hi Satoshi-san,

    i am going to close this thread due to inactivity. Please post back if there is anything else, or open a new thread.

    regards,

    Julian