Re:

Hi Hirut,
I had this discussion with Bob Ross a few weeks ago. This is the
information that he gave me.

Use IBIS Version 3.2 and the [R Series] keyword to model internal
differential
resistor terminations for differential I/O models. That means that you
will
also need the [Series Pin Mapping] keyword to show the connection of [R
Series].

Here is the example that I created using Bob's advice, starting with the
[pin] Keyword and modeling the series resistor between pins 1 and 2:

[Pin] signal_name model_name R_pin L_pin C_pin
  1 PAD lvds_drv NA NA NA
  2 PADN lvds_drv NA NA NA
|
[Series Pin Mapping] pin_2 model_name function_table_group
1 2 rterm_100

|
[Diff_pin] inv_pin vdiff tdelay_typ tdelay_min
tdelay_max
|
   1 2 NA 0 0 0

[Model] rterm_100
C_comp 0.1pF 0.1pF 0.1pF

Model_type Series
|variable R(typ) R(min) R(max)
[R Series] 100 80 120

[Temperature Range] 50.00 125.00 0.00
[Voltage Range] 1.800 1.650 1.950

I have tried it out and the syntax is correct, but you will need to use
a simulator that can understand it. I think that there is a way to do it
with a dynamic clamp, but I think that there may be potential problems
with that. I say this because the voltage at the true and complement
pins are dependent on each other. With the dynamic clamp implementation
I do not believe that this is true.

Regards,
Peter

Hirut Asfaw wrote:
>
> Hi Folks,
> A question regarding *LVDS* I/Os with internal terminations between
> the diff pins.
> When characterizing the Series resistance between the diff pins,
> is the intention to capture the current prior to IBIS generation. Meaning,
> is this part of Spice set up before the IBIS model is generated? or can we
> just include this resistance (as a physical) model once the IBIS model is
> genrated?
>
> Thanks,
> Hirut
>
> Hirut Asfaw
> ASIC I/O Developement
> IBM Microelectronics Division
> External: (802) 769-0652 T/L: 6-0652
> hasf@us.ibm.com

-- 
Peter LaFlamme
Applied Micro Circuits Corp.
Staff System Applications Engineer
200 Minuteman Rd, 3rd Floor
Andover, MA 01810
978-247-8470 phone
978-623-0055 Fax