Re: [IBIS-Users] Modeling Diff Buffers

Hi Anguraj,

I asked similar questions sometime back, but even I didnt get the answers. 
I will try to answer to your first 2 questions
based on my experience.

1. Vdiff value can also be specified under [Receiver Thresholds] keyword. 
So if you have, say 2 speed modes of operation
you need to have two [Model]'s for those 2 modes. As these two modes will 
have separate [Receiver Thresholds] section
you can define 2 separate Vdiff under these 2 modes. The corresponding 
parameter to define Vdiff under [Receiver Thresholds] keyword is

Vdiff_ac =

2. Similarly Common mode range can be specified under [Receiver 
Thresholds] keyword. The parameters corresponds to common mode
range under  [Receiver Thresholds] is

Vcross_low =
Vcross_high = 

For the third question , what i can suggest you is, to check the value 
what you are getting with the datasheet. That should confirm the 
correctness.
Normally we vary the process corner and voltage applied to get the typ, 
min and max values of C_comp.

Let me know if you find these answers helpful.

Best Regards,

Sudarshan HN
NXP Semiconductors/CTO /PLT
C-4, Manyata Tech Park, Nagawara
Bangalore-560 045 , India. 
Ph:+91-80-40267073 
Fax: +91-80-4026 7855
seri:sudarsha@inpsblr
E-mail: sudarshan.honnudike@nxp.com








Anguraj K <b05108@freescale.com> 
Sent by:
owner-ibis-users@server.eda.org
2007-02-02 04:00 PM

To
ibis-users@server.eda.org
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Subject
[IBIS-Users] Modeling Diff Buffers
Classification








Hi Experts,
Could you please answer my below questions?

1. If vdiff value varies for diff pins (due to diff modes of operation, 
namely speed), How do I define that in IBIS models.
Through [Diff Pin] keyword, we can pass only one value to vdiff.

2. How to define common mode value in the diff signals? (I believe there 
are other IBIS users who raised the same question some time earlier)

3. When measuring C-Comp for drivers,
I see three main variables on which die cap depends on.
1. Freq of operation
2. Data value (0 to vdd) to be sent
3. Process corners

I vary these three variables and finding the max and min value for 
C_comp. Is that right?
But,  I usually see very huge die-cap for the drivers(unrealistic)






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