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Max Power of TTL ICs

  1. Oct 25, 2006 #1
    Say I needed 6 D Flip-Flops and wanted to calculate the maximum power dissipated by them. I have 2 Flip-Flops on each IC giving a total of 3 ICs.

    I'd look in the data books and find Vcc max and Icc max and multiply to find the power...

    My Question: would I use Vcc * Icc for every FLIP-FLOP or would I use Vcc * Icc for every IC???
  2. jcsd
  3. Oct 26, 2006 #2
    good morning :

    i think if u want the over all power disepated on ur 3 ics
    ur calculatino would be = Vcc * Icc

    if u want the power which is absorbed by flip flops
    using the data sheet for it >> u can get it >>
    or at least u could find V & I for it

    i hope that i helped u
  4. Oct 26, 2006 #3
    yes, thank you bell12.

    I needed to know that Vcc * Icc gives you the ICs power dis.
  5. Oct 27, 2006 #4


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    I know you said "by" the ics and not "into" the ICs. But if you really meant that you want Vcc max * Icc max then Icc max will depend on both the Iq max of the IC and its loading.

    To understand what I mean consider a flip-flop driving high level to a resistor. The current to create a voltage is going to be much different when the resistor is 1ohm compared to 1Mohm. The power this resistor is burning comes from the Vdd pin of your flip-flop. This current is not spent in the IC but it does travel through the IC so the power source and package of the IC needs to be able to deal with that as well.

    Side Note:
    If the flip-flop is driving a gate you can probably ignore loading power but if you are using one of the ultra low power gates (with Icc=1uA max) then even then it could be a significant extra load depending on your application. i.e. battery shelf life of a product with a really small (low current density) battery.
    Last edited: Oct 27, 2006
  6. Oct 27, 2006 #5


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    Staff: Mentor

    If you want to calculate the power output of a FF, you would look at the Iout @ Vo numbers in the datasheet.
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