[SI-LIST] Re: resend - Specctraquest model: mounted inductance
- From: Larry Smith <Larry.Smith@xxxxxxx>
- To: si-list@xxxxxxxxxxxxx, bart.bouma@xxxxxxxxx
- Date: Tue, 3 Jun 2003 09:22:04 -0700 (PDT)
Bart - Are you looking for the mounting inductance associated with a
decoupling capacitor to be used in the Spectra Quest Power Integrity
tool? SQPI has a fast henry type of EM solver that will estimate the
loop inductance for the Vdd/Gnd terminals. Or, you can do as we do and
measure the loop inductance on an existing product or test board and
insert the inductance manually.
I must confess, I don't really know what to do with 3 terminal
capacitors for the decoupling application. Where do you attach the 3
terminals? Two of the terminals will be Vdd and Gnd, but where does
the third terminal attach to the system? The mounting inductance
for your 3 terminal device will be highly dependent on where the
current is flowing (current and return current).
Does power flow through the 3 terminal device? For example, do you
hook it to Vdd, Gnd and Vdd2? Is Vdd2 a separate power plane in the
PCB stackup? A 3 terminal capacitor used in this way may be very
useful for a sensitive PLL or similar low power application. But the
power consumer will be downstream of the relatively high series
impedance of the 3 terminal device. It may be possible to meet a
target impedance of several ohms using the 3 terminal device, but it
will be very difficult to build a 1 mOhm power distribution system
up to the 100 MHz range using 3 terminal capacitors.
regards,
Larry Smith
Sun Microsystems
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> Subject: [SI-LIST] resend - Specctraquest model: mounted inductance
> From: "Bart Bouma" <bart.bouma@xxxxxxxxx>
> Date: Tue, 3 Jun 2003 08:34:54 +0200
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> Hi all,
> I'm resending this post on Specctraquest mounted inductance. Until now no
> reactions received on this topic.
> Is there no one on the si-list who can help a vendor to generate
> Specctraquest models?
> I read so often that models are not available from vendors, now is your
> chance!
> But I need some help. Please!
>
> Bart
> www.yageo.com
> ================ original post ========================================
>
> Hi all,
>
> I am starting to develop Specctraquest models for three-terminal
> capacitors, e.g. a feedthru capacitor.
> Does anybody know how to extract, or how to determine, the mounted
> inductance of such a three-terminal capacitor?
> Maybe someone already did this?
>
> For a two terminal device the loop-inductance can be determined quite
> easily, but for a three terminal capacitor I could not find a single
> reference.
> Of course it all depends on substrate thickness, vias and layout, but is
> there a general method how to calculate the mounted inductance or
> loop-inductance for such a device?
> Any information is welcome!
>
> regards,
> Bart Bouma
> www.yageo.com
>
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