Re: [IBIS-Users] Modeling Diff Buffers

Hi Anguraj,

You can refer the 4.2 specification document.

http://www.vhdl.org/pub/ibis/ver4.2/ver4_2.pdf          - page 42


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_Kothandapani-b05108 <b05108@freescale.com> 
2007-02-07 06:09 PM

To
Sudarshan Honnudike <sudarshan.honnudike@nxp.com>
cc
ibis-users@eda.org
owner-ibis-users@eda.org
Subject
Re: [IBIS-Users] Modeling Diff Buffers
Classification







Hi Sudharshan,

Thanks a lot for your response!

1 & 2) I tried searching for the keywords in cook book but in vain.Could 
you help me point to the docs/pdfs where I can get all these special 
keywords.

3)  I followed sec 4.7 of IBIS cook book to generate the C-Comp for 
drivers
1. Vary P,V (voltage input to data in), T 
2.  Find the max and min and add them to tables
3. Avg becomes the typ for C-comp

Should I change this methodology?

Once again thanks for your inputs!

Thanks,
Anguraj

Sudarshan Honnudike wrote:

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 
cc

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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