[SI-LIST] Re: Hidden noise margin problems

It takes lot of time and energy for semiconductor vendor to make sure that
ATE testing, IBIS modelling and datasheet remain consistent. As a customer,
one has to demand else there will be mismatch among all three.
regards,
Hiten


On 7/28/06, Lynne D. Green <lgreen22@xxxxxxxxxxxxxx> wrote:
>
> Hello, Tim,
>
> Normally, I would expect the Vih and Vil in the IBIS model to match the
> datasheet.
>
> Having a negative margin in the datasheet sounds like something that
> should
> be brought to the attention of the manufacturer, so they can fix the
> datasheet appropriately.  This could (probably will) also impact their
> in-house testing, etc.
>
> Best regards,
> Lynne
>
>
> "IBIS training when you need it, where you need it."
>
> Dr. Lynne Green
> Green Streak Programs
> http://www.greenstreakprograms.com
> 425-788-0412
> lgreen22@xxxxxxxxxxxxxx
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Nash, Tim J (EHCOE)
> Sent: Thursday, July 27, 2006 5:43 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Hidden noise margin problems
>
> SI Community,
> Is it common for the Vih and Vil on a datasheet to be specified under
> worst-case conditions (70/30% VDD w/ VDD @ min/max conditions), while the
> IBIS model for the part only specifies Vih and Vil at VDD @ nominal (even
> thought the model may have min and max VI and VT corners)?
>
> I've now found this to be the case on two completely different parts from
> completely different manufacturers.  What it seems to create is a
> worst-case
> simulation that appears to behave fine, but a worst-case noise margin
> calculation (based on the datasheet) that has little to even negative
> noise
> margin.
>
> Case in point:
>
> Driver has spec'd Voh = 2.4V and the receiver has a Vih = 0.7 * VDD = 0.7*
> 3.465V = 2.4255V
>
> -25.5 mV of noise margin
>
> However, the net simulates just fine across all corners (model Vih = 2.31)
>
>
> Is this a common problem?  I would think that Vih and Vil in the model
> should match that in the datasheet, especially if is dependant on the rail
> voltage of the part.
>
> Comments?
>
>
> Regards,
>
> Tim Nash
>
> __________________________________
> Timothy J. Nash, P.E.
> Honeywell, Inc.
> Defense & Space Electronic Systems
> 13350 U.S. Hwy 19 N
> M/S 105-4
> Clearwater, FL  33764-7290
> Office : 727-539-2437
> Fax     : 727-539-2183
> Email  :  tim.j.nash@xxxxxxxxxxxxx
>
>
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