Subject: Re: [IBIS] IBIS generation w/ two power supplies
From: Wil Ngan (wngan@idt.com)
Date: Fri Apr 25 2003 - 09:54:57 PDT
Arpad,
I could set [Pullup reference] to 3.3v or 5v, but with what
parameter do I set the main power supply at 5v? (in both
case)
Wil
"Muranyi, Arpad" wrote:
> Wil,
>
> It sounds that your pullup's reference voltage is programmable,
> correct?
>
> In that case, you should use the model selector and make two
> models, on with [Pullup Reference] = 3.3 V, and the other with
> [Pullup Reference] = 5 V.
>
> Arpad Muranyi
> Intel Corporation
> =============================================================
>
> -----Original Message-----
> From: Wil Ngan [mailto:wngan@idt.com]
> Sent: Thursday, April 24, 2003 4:54 PM
> To: ibis@eda.org; ibis-users@eda.org; ibis-info@eda.org
> Subject: [IBIS] IBIS generation w/ two power supplies
>
> hi,
>
> I'm trying to generate an ibis file from a circuit with two power
> supplies, vcc and vccq. Vcc is fixed at 5v, while vccq is either 3.3 or
> 5v, depending on what we would like the output high to be. How do I
> going about doing this?
>
> In the past, I've used [Pullup reference], [Power clamp reference] to
> set vcc to 5v, vccq to 3.3v, respectively. However, I just realized
> that I cannot set vccq using [power clamp reference], since there's
> actually NO power clamp in my circuit. (The ckt only has ground clamp
> transistors, which protects the device from overly low input voltages,
> at same time, that same device works to protect high input voltages
> through breakdown.) I
> had been generating [Power clamp] current table while in fact there is
> no power clamp circuit. Not good. Furthermore, this causes [Pullup]
> current table to be wrong, since [Pullup]currents = I(pullup generated
> by hspice) - I(power clamp), so the numbers in my [Pullup] table are
> actually lower than they should be.
>
> So, going back to the original question, without using [Pullup
> reference] or
>
> [Power clamp reference], how should I go about in providing two power
> supplies to this circuit to generate ibis file?
>
> - Wil
> idt sram, 408/330-1623.
>
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