[SI-LIST] Re: Transmission line capacitance
- From: steve weir <weirsi@xxxxxxxxxx>
- To: rahul kumar <rahul05kumar@xxxxxxxxx>
- Date: Sun, 25 Oct 2009 08:47:28 -0700
If you want to know how much charge is pulled from the PDN each cycle
you can lump the capacitances. If you want to know how your signal is
going to behave, you need to know what your Tr/Tf look like. A lossless
Tx line includes the energy storage, not the energy loss.
Steve.
rahul kumar wrote:
> Hello all,
> Thanks for the reply, i understood it. One more related point to clearify .
>
> I am doing IO driver simulation running at frerquency less that 250
> Mhz . Capacitive load at farend is given equal to 4pF along with
> txline of 3cm. (Z0 = 50, Co = 1.5pF / Cm , Td = 60pS / cm )
>
> 1. Can i take equivalent capacitance to 4pF + (1.5pF *3) = 8.5pF for
> my first order IO calculations. ( Transitions ) .
>
> 2. I am taking ELDO ( simulator ) lossless txline model which takes Z0
> and Td as parameter. By doing this can i assume safely that i have
> taken account of Transmission line capacitance of 4.5pF.
> Or do i need to take lossy transmission line model and ask for more
> parameters.
>
> Thanks for the help.
> Rahul
>
>
>
>
>
> <rtatikola@xxxxxxxxx> wrote:
>
>> Rahul,
>>
>> Definitely not frequency dependent. The units show that it is dependent on
>> the length of the transmission line and calculation is based on
>> cross-section (2D approximation).
>>
>> Ramani
>>
>> On Sat, Oct 24, 2009 at 5:34 AM, rahul kumar <rahul05kumar@xxxxxxxxx> wrote:
>>
>>
>>> Hello all,
>>> I have seen in standards quoting transmission line capacitance equal to
>>> 1.5pF per cm . How this number is calculated?
>>> Is this value frequency dependent? transition dependent ?
>>>
>>> Kindly help.
>>> Suggest link to know more information about the same.
>>>
>>> Thanks
>>>
>>>
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