[SI-LIST] Re: design of on-chip PDN

  • From: "Xu, Catherine (ICS)" <xu@xxxxxx>
  • To: steve weir <weirsi@xxxxxxxxxx>, Siming Pan <pansiming86@xxxxxxxxx>
  • Date: Mon, 1 Nov 2010 23:36:01 +0000

Hi, Siming,

Steve answered well. Using common power net in package design increase risk of:

1) conducted noise due to common impedance coupling - especially for blocks 
contain tens to a couple hundred kHz freq
2) increased coupling due to higher mutual inductance 
3) reduced controllability if all power net are tied together

Using dedicated power island with careful decoupling and PDN control is a much 
better design methodology.


Catherine Xu
__________________________________
Lead HW Design Engineer, Ph.D
HP ICS  CHIL - San Diego
__________________________________ 


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of steve weir
Sent: Monday, November 01, 2010 4:24 PM
To: Siming Pan
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: design of on-chip PDN

Common impedance.

Steve.
Siming Pan wrote:
> Hi All,
>    I have a basic question related to on-chip PDN design. Usually the supply
> voltages are designed to be isolated for core, SERDES
>
>  digital, analog, termination, etc. This design may isolate the SSN
> couplings among each net. However, usually large on-chip decoupling
>
>  capacitances are used for VDD core circuit. In the board design, we connect
> the power nets of VDD_core together with VDD_digital¡£
>
> Thus, switching noises generated from SERDES digital are suppressed by large
> on-chip decaps designed for core circuit. However,
>
> package inductances  still play a bad role here to block the conducted path
> between noise source formed by digital circuit and core
>
> capacitances. Then why not use one common power net as the supply power for
> all the IC circuits, so that large on-chip decaps can be
>
> shared, if the voltage levels are the same?
>
> Regards,
>
> Siming Pan
>
>
>   


-- 
Steve Weir
IPBLOX, LLC 
150 N. Center St. #211
Reno, NV  89501 
www.ipblox.com

(775) 299-4236 Business
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