[SI-LIST] Re: Has the performance of the PDN in the receiver little effect on the SSN?
- From: steve weir <weirsi@xxxxxxxxxx>
- To: xuzhengrong <Zhengrong.Xu@xxxxxxxxxx>
- Date: Wed, 09 Jul 2008 03:27:41 -0700
Xuzhengrong, if the receiving device doesn't have many drivers
switching, then as long as the receiver reference is bypassed to signal
return image plane ( usually Vss ), then the receiver tracks the
arriving signal. The problems arise when there is lots of switching
current from active outputs in the receiver package. That impresses
noise in the interconnect between the die and any image plane on the PCB
that serves as the signal return.
Steve.
xuzhengrong wrote:
> Hi all,
>
> As we know, SSN arises from PDN noise and crosstalk. Here I just talk about
> the effect of PDN noise.
>
> In some SSN simulation, I find that the PDN in the driver side plays the
> dominant effect on SSN and the PDN in the receiver side plays little effect.
>
> My explanation is as follows.
>
> The following picture is a simple topology consisting of IBIS buffer models.
>
>
> We know that large current will be pulled up or pulled down when a large
> number of IOs switch simultaneous
> and generate large PDN noise which aggresses quiet pin or stable level
> through the path of PDN.
>
> However, the level changes only by C_comp charging or discharging in the
> input buffer (clamp diodes also play a little effect on the waveform)
> instead of pulling up current or pull-down from PDN like the output buffer.
> Maybe there are also some noise in the node of nd_pc and nd_pc in the
> receiver, but the noise hardly aggress signals in the receiver.
>
> Therefore the performance of the PDN in the receiver has little effect on
> the SSN.
>
> And I just learn from books that SSO(simultaneous switching output noise )
> is SSN and haven't seen the knowledge about the SSN in the receiver yet.
>
> Is there any problem in my explanation? Can I make a conclusion that the
> performance of the PDN in the receiver has little effect on the SSN?
>
> Appreciate any idea on it.
>
>
> output buffer
> input buffer
> --- ------------------------------------------------------
> ----------------------------------
> | nd_pu nd_pc |
> | nd_pc |
> | ___|___ ___|___ |
> | ___|___ |
> | ---|__PU__| |__PC__| C_comp | ____
> __________ ____ | C_comp |__PC__| |
> | ____| |________|_____________|_| pkg |___{ Tline
> }_| pkg |__|______________| |
> | nd_in | ___| __ ___|___ __|__ | |____|
> {_________} |____| | __|__ ___|___ |
> | ---|__PD__| |__GC__| ____ |
> | ____ |__GC__| |
> | | | _|_
> | | _|_
> | |
> | nd_pu nd_gc = |
> | = nd_gc |
> ------ ----------------------------------------------------
> -----------------------------------
>
>
> Best Regards,
> Zhengrong
>
>
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