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Power consumption of a PCB

Discussion in 'General Electronics Discussion' started by andrewm37, Sep 28, 2012.

  1. andrewm37

    andrewm37

    4
    0
    Sep 28, 2012
    Hy!

    I designed a PCB and now I would like to determine the current consumption and the power dissipation. I know that there is there factors that define these things: static, dynamic, switching. Static is quite easy for example I have a MOSFEt and a do this : Ps= IDss*V
    Dynamic is when I Pd=Cpd*V^2*fout , and I have problem with the switching one:
    The equation states this: Ps= CL*V^2*fout. Where CL is the load capacitance. I have 2 0.1u, 1 10u and 1 10p cap connected to my P-mos to reduce inrush. What i did is that I added these caps as paralell ( ~10.2u) and substituted it back to the equation as CL. My V is 5Volt and fout is ~ 25 Mhz (1/ton). This gave me a huge dissipation : 6375 W :eek:, I am sure I miscalculated something. Any suggestion. This is the P-mos datasheet:
    http://www.vishay.com/docs/72024/72024.pdf
    And this is where I got the info how to calculate power consumtion:
    http://www.ti.com/lit/an/scaa035b/scaa035b.pdf
     
  2. davenn

    davenn Moderator

    13,249
    1,746
    Sep 5, 2009
    Hi Andrew
    Welcome to the forums

    your capacitance is going to be 10.10001uF .... for practical purposes the 10pF is so small in value it doesnt really add anything significant to the overall capacitance
    its only 0.00001 uF

    can you not just do some basic current measurements ?

    Dave
     
  3. andrewm37

    andrewm37

    4
    0
    Sep 28, 2012
    How do you mean that?
     
  4. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Like this, the 'lamp' represents your circuit...

    [​IMG]
     
  5. andrewm37

    andrewm37

    4
    0
    Sep 28, 2012
    Yes, but I would like to measure it in theory chip by chip.
     
  6. wingnut

    wingnut

    233
    8
    Aug 9, 2012
    Have you tried a simulator like LTspice?
     
  7. andrewm37

    andrewm37

    4
    0
    Sep 28, 2012
    Yes but not for measuring power. According to the datasheet the power can be calculated if you know certain parameters like Cin Cload Cpd Icc Fout and of course the supply voltage.
    But I'm stuck where I wrote that in my original thread.
     
  8. wingnut

    wingnut

    233
    8
    Aug 9, 2012
    Your maths is correct to get 6375W, so there must be something wrong with your data or equation for Ps surely?
     
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