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LM5156H-Q1: Power management forum

takahiro.yoshida02
Prodigy 20 points
Part Number: LM5156H-Q1
Other Parts Discussed in Thread: LM5156H

Hi Team,

would you share your mailing list for sending email？

due to our company's information security policy,  I would like to ask you refrin from the publishing my question.

Best regarfs.

  • 0
    TI__Genius 16535 points

    Hello takahiro-san,

    Thanks for using the e2e forum.

    May I please ask you to follow these steps:

    - Register properly on the forum. No "??" entries, please.

    - Post your question including all possible information (VINmin, VINmax, VOUT, IOUT, etc.) as detailed as possible.

    - In that post, mention that there may be additional information required which you cannot share publicly (e.g. schematics). 

    - We can then start a protected, private chat from within that thread.

    I am closing this thread now, because when you register with a proper name, this thread here will be obsolete anyway.

    Thanks and regards

    Applications Support Team

  • 0
    Prodigy 20 points

    Hello,

    Thank you for your reply,

    I think, the forum NO. became properly. so, please keep this thread. I will add the information in this thread.

     

    The schematics is boost converter.

    -Vin max; 16V, Vin min; 8V, Vout ; 25V

     then, we have 2 spec. of Iout , spec. 1 is Iout =0.7A, spec. 2 is Iout =0.05A.

    -switching freaquency is 2MHz

    -Qg of extarnal FET is 17nC

    -Inductor  spec. 1 is 10μH, spec. 2 is 33μH

    then ,  my question is the possiblity whch we use VCC of LM5156H-Q1 for other schematics.

    Current amount of other schmatics is 0.2A.

    other schmatics is LDO regulator. we want to make 5V from VCC of LM5156H.  

    please give me the feedback to my question.

    Best regards.

  • +1 in reply to takahiro.yoshida02
    TI__Genius 16535 points

    Hello takahiro-san,

    I am sorry, but the internal regulator of our controllers / converters cannot be used to drive additional external circuitry. 

    The only reason why the VCC capacitor (and in case of synchronous converters also the bootstrap capacitor) is external, is because it would not fit into the package.
    This capacitor is purely meant as an energy storage for the gate driver. High current pulses are drawn from this capacitor to drive the gate of the FET.

    The internal regulator is dimensioned just to deliver enough current for the gate driver. 

    Especially in case of 2MHz switching frequency there will be a lot of energy drawn from that capacitor. 

    Only some configuration / mode pins of the same controller IC are allowed to be connected to the VCC pin (mainly to make sure that the voltage on these configuration pins will not be too high).

    In the opposite direction, when the input voltage is high and there will be a big voltage drop on the internal regulator, you can feed an external voltage into the VCC pin. This will disable the internal regulator and help to distribute the losses and thermal dissipation to an external device.

     Long story short: Please do not use the VCC pin to drive any additional external circuitry. 

    Best regards

    Harry