switching capacitance

[abir]

Posted on June 08, 2010 at 10:50

switching capacitance

[chikos332]

Posted on May 17, 2011 at 13:54

Hi again,

I don't know if it is interesting for you, but you may use the values given in table 16 in the STM32 datasheet

http://www.st.com/stonline/products/literature/ds/14611.pdf

... you may use the input current instead of the voltage and the capacitance ... Also in Table 10 you may find the value of the power dissipation at 85°C and 105°C ... Cheers.

[chikos332]

Posted on May 17, 2011 at 13:54

Hi Abir,

I don't have an answer but I am interested to know: Is it possible/feasible to measure this kind of parameters (switching capacitance/dynamic power ...) for complex components like microcontrollers ? I thought it was reserved for analog components or for components having simple architectures (STM32 has internal power controllers, PLLs, multiple pins types, multiple power modes ...). I'd be thankful if you clarify this point for me :) Cheers.

[abir]

Posted on May 17, 2011 at 13:54

hi,

You mean that i should compute the power P=U*I? Concerning table10, i don't know if they talk about Pstatique, Pindependent from frequency or else? Cheers

[chikos332]

Posted on May 17, 2011 at 13:54

There is one question you should ask yourself: Why do you need such computation ? In which way do you intend using the obtained result ? (I presume it is for an educational work)

You should be aware that power consumption depends on really MANY parameters: voltage, temperature, package type, boot mode, CPU frequency, number and types of peripherals in use, IOs configuration, memories, external devices, run/stop modes ... and even the software that is running on the microcontroller... So I don't advise you to use formulas like P=X*y*Z in these cases it seems to me really obolete, you may just consider some typical cases/some limited configurations... It is more appropriate to perform measures on the chip to have concrete results and make some statistics or something like that... But If you really need using formulas, in Table 14 and 15 you have input current dependent on Frequency so it may be useful for you (P=V*I) to compute static power for each range of frequency (instead of dynamic power)... But again, I don't think it would be a good idea for your work ... you may use the values but not the formula... I hope these advises may help you... Don't hesitate to ask more questions, there should be someone on the forum who have more accurate or better ideas :) Cheers.