Subject: RE: [IBIS-Users] C-Comp
From: Birendra Rana (birendra.rana@wipro.com)
Date: Mon Jul 21 2003 - 02:40:25 PDT
Hi Anshuli,
The C_comp parameter is a bit confusing at first but I hope this
explanation will set it right :
The C_comp parameter tells the simulator what capacitance it should
expect when looking "into" the model. The tables in the IBIS model
wouldn't have that Info. To get the feel of the C_comp parameter try
simulating a I/O buffer IBIS model with a transmission line with a
termination resistor and a capacitive load. Take the IBIS model with
C_comp = 0 pF and other case with C_comp = some value. You will see the
difference in the waveforms as reflected output signal will encounter
this 'capacitance' of the buffer in the second case.
Hope this clears.
Birendra
-----Original Message-----
From: Anshuli Goel [mailto:anshuli@ti.com]
Sent: Monday, 21 July 2003 2:49 PM
To: Muranyi, Arpad; 'ibis-users@eda.org'
Subject: Re: [IBIS-Users] C-Comp
Arpad
As far as I understand the C_comp value is not taken into account for IV
curve calculation , it is only added in the calculation in VT curve , so
while calculating VT curve we already have capacitance , why do we need
to put C_Comp ??
Anshuli
"Muranyi, Arpad" wrote:
> That is because the IV curves do not exhibit any capacitive behavior,
> they are only DC. In order to put the capacitive effects into the
> IBIS model we need to add a capacitance to the IV curves.
>
> Arpad Muranyi
> Intel Corporation
> ===========================================================
>
> -----Original Message-----
> From: Anshuli Goel [mailto:anshuli@ti.com]
> Sent: Friday, July 18, 2003 6:16 AM
> To: 'ibis-users@eda.org'
> Subject: [IBIS-Users] C-Comp
>
> Hello Experts
>
> I have one naive question.
> While defining the C_Comp we say "C_comp defines the silicon die
> capacitance. This value should not include capacitance of
> the package.The C_comp capacitance must represent what you see when
> you look into the die at the die pad. This includes the die pad, metal
> connections on the die, the driver transistor's capacitance, the
> receiver (input)capacitance, everything that is on the die."
>
> But my understanding is that anyway the netlist is going to have
> driver transistors in it in case of buffers, why do we need to account
> for the capacitance for driver transistors ?? I can understand about
> the metal connection and bond pad capacitance ,but I am not able to
> understand the Transistors Capacitance part of it . Please clarify.
>
> Regards
> Anshuli
>
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