[SI-LIST] Re: Chip capacitance effect for SSN simulation
- From: Cristian Gozzi <cristian.gozzi@xxxxxxxxx>
- To: Poorna Chander Ravva <poornachander.ravva@xxxxxxxxxxxxxxxxxxxx>
- Date: Sun, 16 Oct 2011 19:56:14 +0200
Hi folks
I'm realizing that there was some misunderstanding on description of my
system
attached 2 reference pictures about Probe Card system and PDN for this kind
of application
(Note: for those that wants to go deeply inside of this kind of system can
check my presentation at IEEE SWTW 2011:
http://www.swtest.org/swtw_library/2011proc/PDF/S08_03_Gozzi_SWTW2011.pdf )
For Main PCB and Interposer I'm using SIwave, while for needles I'm using
HFSS since is a pure 3D structure so I cannot do any simplification
so the only way to simulate the whole PDN system was to make a pin sub-group
of DDR pwr and simulate only 6 pwr needle with HFSS
(I selected only those pwr needles that are around my 10 DQ)
Finally I combined entire system in SPICE deck and simulate transient SSN
I always simulate in both frequency and time domain.
Question: where is the IBIS section where I can find out my pwr die
capacitance?
I only was aware of C_comp that should be the parasitic capacitance of out
buffer, isn't it?
Thanks
Cris
2011/10/16 Poorna Chander Ravva <poornachander.ravva@xxxxxxxxxxxxxxxxxxxx>
> Hi Cris,
> 1. As far as I know the IBIS model should include the one die capacitance
>
> 2. May be you can just confirm with the silicon vendor
>
> 3. Also the frequency range of the anti resonance for your PDN is
> important. If the resonance is generally around 1GHz range, then it might
> be contributed because of the lack of the on die capacitance.. if the
> resonance is much much lower in frequency it is contributed by either the
> lack of your package capacitance (since you did not include that anyway)
> and or board capacitance
>
> 4. Regarding the HFSS simulation: if you are generating your whole power
> delivery network model in HFSS it would be very difficult to solve. I
> would use tools like PowerSI or Ansoft SIwave to generate the PDN models
> and then incorporate the connector models from the HFSS into your final
> SSN SPICE simulation...
>
> Thanks,
> PoornaChander Ravva
>
>
> > Hi folks
> >
> > thanks for your feedback.
> > I had to reduce the number of power pins in HFSS simulation otherwise the
> > full 3D model with all power pins was to huge to simulate.
> >
> > So I reduced 46 pwr needles of I/O pwr to only 6 around of my total 10
> I/O
> > I'm simulating for SSN.
> >
> > Cheers
> > Cris
> > Inviati dal mio telefono Nokia
> > ----Messaggio Originale----
> > Da: Michael Greim
> > Inviati: 16/10/2011, 15:13
> > A: steve weir
> > Cc: si-list@xxxxxxxxxxxxx
> > Oggetto: [SI-LIST] Re: Chip capacitance effect for SSN simulation
> >
> >
> > Great points Steve (as always). Cristian, a simulation
> > is only as good as its ability to properly mirror the actual
> > correlated test setup. As you strip this that and the other
> > thing out, the sim and the hardware behavior will become very
> > different from one another. Set up some test cases with
> > your queries and see if the behaviors are convergent or
> > divergent.
> > Why did you "have to" reduce the number of power pins?
> >
> > Build up a better relationship with your vendor and tell them
> > what you are looking for and why and you might be quite
> > surprised what they give you. Perhaps even an RLC matrix
> > or two and with a story relating of other customers who have
> > run into similar issues.
> >
> > Check out my quote from Mr fleischmann below. Works
> > great for a number of things in real life and the simulated
> > behavior thereof including SI/PI sims.........
> >
> > -Michael.
> >
> > We will either find a way or make one -Hannibal
> >
> > In the middle of every difficulty lies opportunity -Al Einstein
> >
> > If you're not getting the results you want with the
> > current approach, move on and try something else. -A. Fleischmann
> >
> >
> > On Sun, Oct 16, 2011 at 5:39 AM, steve weir <weirsi@xxxxxxxxxx> wrote:
> >
> >> You need a model of the silicon that includes the on-die capacitance.
> >> You can try to obtain this, or if it is not available, then derive it
> >> from measurements. The complexity of the model that you construct
> >> depends on how much accuracy you need. You will still face the same
> >> challengess as others in the ATE business when dealing with the parallel
> >> bus structure of DRAM switching with very small rise and fall times, and
> >> the inductance of your probing interconnects.
> >>
> >> Steve.
> >>
> >> On 10/16/2011 2:25 AM, Cristian Gozzi wrote:
> >> > Hi SI members
> >> > I'm simulating DDR2 SSN for a Probe Card system
> >> >
> >> > for those that are not familiar with this application, Probe Card is
> >> an
> >> > hardware application to physical connect DIE pads/bumps at wafer level
> >> to
> >> > ATE system during Electric Wafer Sort
> >> > In my case Probe-Card is build by a vertical needles that touch DIE
> >> pads
> >> +
> >> > PCB
> >> >
> >> > During frequency domain analysis of my system, I got a strong PDN peak
> >> > impedance around 1GHz
> >> > This peak impedance was due to anti-resonance effect between PCB PDN
> >> system
> >> > and needle PWR parasitic effect
> >> >
> >> > so during time domain analysis I got a strong and unreasonable AC
> >> noises
> >> > also with only 2 switching DQ
> >> >
> >> > In my spice deck I only used IBIS model provided by silicon vendor and
> >> I
> >> > excluded RLC package effects, since my application is contacting
> >> directly
> >> > wafer.
> >> >
> >> > I think I should include chip power rail capacitance effect in order
> >> to
> >> > filter high freq noises.
> >> >
> >> > But my question is: which C and R value should I use?
> >> >
> >> > Is these value included in IBIS model?
> >> >
> >> > NOTE: consider that I had to reduce number of PWR needles used for
> >> HFSS
> >> > simulation, so I only selected those needles around my 8 DQ + 2 DQS
> >> >
> >> > So I think I should put a lower value of chip capacitance than total
> >> one
> >> >
> >> > Any comments from expert are more than welcome
> >> >
> >> > Thanks in advance
> >> >
> >> > Regards
> >> > Cris
> >> >
> >> >
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> >>
> >> --
> >> Steve Weir
> >> IPBLOX, LLC
> >> 150 N. Center St. #211
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> >>
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> >>
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> >
> >
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> >
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