[SI-LIST] : Adding inductors to ground?

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From: Chris Bobek (cbobek@cadence.com)
Date: Wed Mar 01 2000 - 14:14:49 PST


Hi,

I came across a schematic that shows the PLL ground of an IC connected
to ground through an inductor. The Vcc pin of the device is connected
to a bunch of caps and an inductor to Vcc.

I understand and have used an inductor (or a resistor) with a bunch of
decoupling caps on Vcc for applications like this. But, I've always
tied the Gnd pin(s) directly to ground. It doesn't make any sense to me
why you would want to add inductance in the path of any ground. It
seems you would just add switching noise to your device.

Can somebody explain whether this is common practice, or whether it was
a poor design (sorry I don't have more information on the particular
device).

Thanks,

Chris

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