[SI-LIST] Re: Decoupling Using 3-Terminal Capacitor

Hello Tom,
Thanks for your valuable inputs. I thought about
connecting the 3-terminal caps in series or in
parallel.

Series and parallel arrangement is shown in the
attached text file.

Out of these two arrangements I think it is better to
have the series arrangement. COnnecting them in series
is like cascading filters. Further, the series
arrangement should offer higher reverse isolation than
the parallel arranagement. 

Sincerely

Himanshu Arora


--- Tom Dagostino <tom@xxxxxxxxxxxxx> wrote:
> You might want to think about parallel and series
> circuits.  In parallel
> circuits the total impedance is less than putting
> the same two impedances in
> series.  And, yes, yes, I know there are resonance
> issues that will make
> that not a general case.
> 
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of
> Himanshu Arora
> Sent: Tuesday, May 31, 2005 2:45 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Decoupling Using 3-Terminal
> Capacitor
> 
> 
> Hello,
> I am making a prototype PCB where in there are
> multiple VDDs.
> 
> The Power Supply filter network looks somewhat like
> the one shown in the figure attached in text file.
> Instead of 2 terminal caps I plan to use the
> 3-terminal cap. The 3-terminal caps are from Murata.
> 
> The reason of using 3-terminal caps against
> 2-terminal
> Multi-layer-ceramic caps is that they offer lower
> ESR
> at SRF, their lead inductance is lower and their SRF
> is higher for the comparable cermic cap in value and
> case size. The reason I am connecting the two
> 3-terminal caps in series is to offer a lower
> impedance across a wide range of frequencies.
> 
> I would like to have your views and inputs for the
> above arrangement. Thanks.
> 
> Sincerely
> 
> Himanshu
> 
> 
> 
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> 
> -- Attached file included as plaintext by Ecartis --
> -- File: 3tcap.txt
> -- Desc: 2302733855-3tcap.txt
> 
> 
>       VDD                     C1              C2
>                               ----            ----
> 
>
|--------Ferrite------------------------------------VDDA
>       |                       ----            ----
>       |                        |               |
>       |                        |               |
>       |                       GND             GND
>       |
>       |                       ----            ----
> 
>
|--------Ferrite------------------------------------VDDD
>       |                       ----            ----
>       |                        |               |
>       |                        |               |
>                               GND             GND
> 
> 
> C2 = 2200pF (NFM21CC222R1H3)
> C1 = 1uF    (NFM21PC105B1A3)
> 
>
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-- Attached file included as plaintext by Ecartis --
-- File: 3tcap.txt
-- Desc: 2302733855-3tcap.txt

SERIES ARRANGEMENT of C1 and C2

        VDD                     C1              C2
                                ----            ----
        |--------Ferrite------------------------------------VDDA
        |                       ----            ----
        |                        |               |
        |                        |               |
        |                       GND             GND
        |
        |                       ----            ----
        |--------Ferrite------------------------------------VDDD
        |                       ----            ----
        |                        |               |
        |                        |               |
                                GND             GND


C2 = 2200pF (NFM21CC222R1H3)
C1 = 1uF    (NFM21PC105B1A3)


********************************************************************
PARALLEL ARRANGEMENT of C1 and C2

                                                GND
                                                 |
                                                 |
                                                ----
                                         ---------------
                                        |       ----    |
                                        |               |
       VDD                              |        C2     |
                                        |       ----    |
        |--------Ferrite------------------------------------VDDA
        |                                       ----    
        |                                        |      
        |                                        |      
        |                                       GND
        |
                                                
        
                                                
                                                 
                                         
                                        

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