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LM2650 SD, SLEEPLOGIC Pin Configration?

m.k
Intellectual 2650 points
Other Parts Discussed in Thread: LM2650

Hi SimpleSwitcher expart,
   I have post this question in Non-Isolated DCDC Forum yesterday.
   Let me post  again in SimpleSwitcher Forum.
----
 Customer pulldown SLEEPLOGIC Pin with 10Kohm to GND.
Is this OK?
I think these logic pins pullup with current source internally.
I would like to confirm the LM2650  Logic Pin Input cofigulation.
How is the internal pullup current or resistor?

Please advice me.
Matsuro/JPIC

  • 0
    TI__Intellectual 1775 points

    Hi Matsuro-san,

    You are correct, there is an internal pull-up current source. We are looking into the strength of that pull-up but in general, we advise the user to use a 0ohm pull-down resistor if possible.

    Is there a reason for the customer wanting resistance between this pin and GND?

    Best Regards,

    Florent Boico

  • 0 in reply to Florent Boico
    TI__Intellectual 2650 points

    Hi Florent,
       
          Thanks you for your responce.

          The reason I asked is ;
    SLEEP LOGIC Pin looks "Forced Sleep Mode" , "Forced PWM Mode", Sleep-PWM Mode"  to me.
    But LM2650 D/S does not mention about SLEEP Pin cofigration except VILmax, VIHmin.
    My understanding
    SLEEP Pin = Low    then     "Forced Sleep Mode"
    SLEEP Pin = High    then     "Forced PWM Mode"
    SLEEP Pin = Open    then    "Sleep-PWM Mode" (light load:Sleep, heavy load:PWM)
    I thougt if the simple internally pullup current makes Pin high(PWM Mode) when Open.

    So,  I wonder that SLEEP Pin input configuration may distinguish these 3-Mode somehow.

    Maybe the designer issue.
    If you know some, please share me.
    Thanks,
    matsuro/JPIC

  • 0 in reply to m.k
    TI__Intellectual 1775 points
    Actually, it's a little more complicated as the part is designed to have the ability to alternate between light load and PWM operation if the pin is left floating so there are a few interactions with internal signals at this node.

    Depending on the conditions, it looks like the pin can be internally pulled-up or pulled-down. That's why we would recommend the pin be firmly pulled down or pulled up externally to avoid any confusion in operation mode (with a 3rd option being of course, leaving the pin fully floating).

    Best Regards,
    Florent
  • 0 in reply to Florent Boico
    TI__Intellectual 2650 points
    Hi Florent,
    I understood and agree with you.

    Thank you very much,
    matsuro/JPIC