• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 472 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

LM5007 - addtion of the capacitance at SD pin

Hirotaka Matsumoto
Guru 27585 points
Other Parts Discussed in Thread: LM5007

Hi all

Would you mind if we ask LM5007?

<Question>
Our customer would like to add capacitance at SD pin for the input voltage which is the extremely‎ gradual rise.
(We think that the start up of  the device will be unstable because of extremely‎ gradual rise.)
So, do you have the experience of addtion of the capacitance at SD pin?

And then, the data sheet shows that Remote Shutdown Thresholds are  0.45Vmin,0.7Vtyp and 1.1Vmax.
Our customer uses Ron resitance 15kohm.
In this case, how much will Remote Shutdown Hysteresis be?
(Our customer hope that it(Hysteresis) is less than 40mV.)

Kind regards,

Hirotaka Matsumoto

  • 0
    Guru 27585 points

    Hi team 

    LM5007 is the old device, but if you have some advice, could you let us know it?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Intellectual 2320 points
    Hello Matsumoto-san,

    Sorry for the late reply.

    What value of the capacitor does the customer plan to use in the schematic? Can you please share the schematic and the input and the output voltage requirements?

    Are you planning to use the RON/SD pin for delayed starting of the part? The capacitor, the RON resistor and the low internal impedance determines the delay time constant . With a capacitor there, you will end up adding a delay in the start-up time. The part will start up only when the RT/SD pin measures more than 0.7V typ. However, there may be unpredictability in the way the part responds during load and line transients in this case. There may be some chattering on the Vout as well. Also the slew rate of the VIN will also determine the delay injected with this circuit. However, the TON values will remain unchanged.

    The shutdown hysteresis is not dependent on the RON resistor value. It should remain the same irrespective of the RON value.

    Regards,
    Sourav
  • 0 in reply to Sourav.Sen
    Guru 27585 points

    Sourav san

    Thank you for your update!

    We appologize that we did not hear what value of the capacitor the customer plans to use in the schematic.
    And Vin is 24V, Vout may be 5V.
    We will check these after that, we will feed back.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Sourav.Sen
    Guru 27585 points

    Sourav san

    We update following information;
    -Vin : 24V
    -Vout : 5V or 12V(two type)
    -Capasitance : Undecided(TBD), but  from 1 uF to 100uF

    Kind regards,

    Hirotaka Matsumoto