[SI-LIST] Re: IO Power Dissipation in SoC
- From: David Utah <telegrapher9@xxxxxxxxx>
- To: Ajay.Dhingra@xxxxxxxxxxx
- Date: Fri, 1 Aug 2014 10:23:28 -0600
When charging/discharging a capacitive load the energy dissipated is
voltage squared times the load capacitance (plus the driver C). Note that
energy is dissipated both on charging and discharging the capacitance and
that's why the 1/2 in the equation you cite, goes away.
W = (V^2)C
For a resistively terminated load use (V^2)/Rload + (V^2)Cdriver
Dave Cuthbert, NARTE Certified EMC Engineer
Consultant for analog, instrumentation, power conversion, EMC
On Fri, Aug 1, 2014 at 3:10 AM, Ajay Dhingra <Ajay.Dhingra@xxxxxxxxxxx>
wrote:
> Hi All
> I was wondering if someone can put a thought on how to calculate power
> dissipation in the I/Os(Buffer Drivers) of an SoC. Will it be
>
> Buffer I/O Supply Voltage(VCCQ) * I/O Current
>
> Where I/O Current is as per the drive capability of driver(drive strength).
>
> OR it will be
>
> =1/2 *{CVF}* V
>
> Where C is the load cap
> V is the I/O voltage amplitude
> F is the toggle frequency of I/O.
>
>
> OR
>
> Both the proposals are wrong. Kindly educate me.
>
> Point to note: in first proposal current is independent of Load whereas in
> second current depends on Load Cap.
>
> Thanks
> Ajay Dhingra
>
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