Re: [SI-LIST] : Crow bar current (dc switching current) vs power

Vinu Arumugham (vinu@cisco.com)
Wed, 15 Jul 1998 12:33:15 -0700

Hi Elias,

We have seen significantly different levels of power rail noise when
devices from different vendors were dropped into the same circuit. In
this case, the device was a lightly loaded (~80 ohm per output) clock
driver. The most likely cause for the higher noise level with some of
those devices, is their higher crowbar current. Such parts therefore
increase the demands on the high-frequency power distribution system.

Thanks,
Vinu

Elias Lozano wrote:

> Hi everyone:
>
> I have a question and I would like to get some answers from the
> experience of so many of you.
> If the I/O's have some crow bar current (when N and P are momentarily
> on) what is the problem in terms
> Of Noise or Power? Has anyone measured this effect?
>
> Here are the questions:
>
> 1) Will crow bar current make your chip noisier and by how much?
> 2) Will crow bar be more a problem with power dissipation of the
> chip?
>
> Please let me know what anyone thinks
>
> Thanks
>
> Elias