Subject: RE: On chip Active termination

From: "Peters, Stephen" <[email-masked]>
Date: Mon, 16 Apr 2001 09:56:19 -0700

Hi Prasad:

  If by 'controlled impedance' you mean builing termination resistors or
clamps on die then yes, IBIS does support this.  Simply include the on die
termination in the circuit when extracting the I/V data for the [Gnd Clamp]
or [PWR Clamp] curves.

  Also, everyone please note that for vendor specific tool questions you
should contact the vendor directly.  Per EIA policy, the ibis-users and ibis
reflectors are for IBIS related discussions only.

  Regards,
  Stephen Peters
  Intel Corp.
  Vice Chair, EIA/IBIS Open Forum

-----Original Message-----
From: Prasad Rau [mailto:[email-masked]]
Sent: Friday, April 13, 2001 5:58 PM
To: [email-masked]
Subject: On chip Active termination

Hi,

On our current design we support several standards using controlled
impedance. By using this scheme
we can mimic driver or receiver end terminations for standards like
SSTL,HSTLs
and GTL. The onchip termination is done using active devices as opposed to
passive
elements.  For example in the SSTL2 Class I the parallel termination is at
the receiver end.
Using the controlled impedance scheme we can eliminate the series & parallel
termination resistor son the board.
I have created seperate IBIS models for the output and the input. When I use
the output model
and drive the input model through a Tline using the HyperLynx tool I am not
seeing the right
levels at the receiver end. It is telling me that the termination at the
receiver is missing. I know
that the input IBIS model makes sense because if I look at the GND clamp
curve I observe ~ 0mA
current at 1.3V ( which is the valid voltage level with the output
tristated). The same driver model
if it drives a non controlled impedance receiver with the appropriate board
termination at the receiver
gives me the correct levels at the receiver.

 Is HyperLynx unable to recognize onchip termination input IBIS models ? Has
aynone
worked with controlled impedance and have suggestions in modelling them in
IBIS.

Appreciate your help in this regard.

Thanks in advance,

Regards,

Prasad Rau
Xilinx

---

From: Prasad Rau <[email-masked]>
Date: Mon, 16 Apr 2001 11:23:55 -0700

Hi Stephen,

Thanks for your feedback. My intention was to make sure I was not
making a modelling mistake before I questioned the tool. I should have
perhaps, framed my questions differently. My apologies to the IBIS
community.

Regards,

Prasad