Venu, I am sorry, but I am not sure what to say now, because I don't understand what you are referring to as "pre-drivers section delay". Please clarify. Thanks, Arpad ================================================== ________________________________ From: Ummalaneni, Venu Babu (Venu) [mailto:venubabu@agere.com] Sent: Thursday, February 09, 2006 9:32 PM To: Muranyi, Arpad; ibis-users@eda.org; ibis@eda.org Cc: Kotikalapudi, Shiva Kumar (Shiva) Subject: RE: [IBIS-Users] RE: [IBIS] To capture the delay variation with change in IO voltage Arpad, I have tried with the 'scal' parameters that you have mentioned. Still correlation has not improved. I hope the pre-driver section delay, that influenced by IO voltage, may not scale by this option. I think "non-scalable pre-driver section delay" is one of the main causes for the mismatch in delay of IBIS vs spice models during IO voltage noise simulation. Please let me know your views. Thanks, Venu -----Original Message----- From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Muranyi, Arpad Sent: Wednesday, February 08, 2006 11:10 PM To: ibis-users@eda.org; ibis@eda.org Subject: RE: [IBIS-Users] RE: [IBIS] To capture the delay variation with change in IO voltage Venu, I just remembered something that I forgot to mention in my previous reply. This is not an IBIS parameter, but HSPICE does have something in the B-element which tries to imitate the gate modulation effect. Look at the last two items on this list: B_IO nd_pu nd_pd nd_out nd_in nd_en V_out_of_in [nd_pc nd_gc] + file='file_name' model='model_name' + [typ={typ|min|max|fast|slow}] [power={on|off}] + [buffer={3|input_output}] + [xv_pu=state_pu] [xv_pd=state_pd] + [interpol={1|2}] + [ramp_fwf={2|1|0}] [ramp_rwf={2|1|0}] + [fwf_tune=fwf_tune_value] [rwf_tune=rwf_tune_value] + [nowarn] + [c_com_pu=c_com_pu_value] + [c_com_pd=c_com_pd_value] + [c_com_pc=c_com_pc_value] + [c_com_gc=c_com_gc_value] + [pu_scal=pu_scal_value] + [pd_scal=pd_scal_value] + [pc_scal=pc_scal_value] + [gc_scal=gc_scal_value] + [rwf_scal=rwf_scal_value] + [fwf_scal=fwf_scal_value] + [spu_scal=spu_scal_value] + [spd_scal=spd_scal_value] They are scaling coefficients which scale the IV curves based on the change in the supply voltage. They are not documented too well in the HSPICE manuals, but as far as I remember they will do the following: If you have a value of 1, the IV curve will be scaled by the same percentage as the supply deviates from the value given by the IBIS model. For example, a 5V buffer getting 4.5 volts means a 10% change down, so the IV curve will be reduced by 10%. If you give 0.5 for these parameters, the same 10% change in the supply will result in 5% change in the IV curve. A zero will result in no change in the IV curves, a 2 will result a 20% change, and so on... As far as I remember, negative values will also work reversing the relationship (lower supplies will increase the IV curves). I hope this helps. Arpad =============================================================== ________________________________ From: Ummalaneni, Venu Babu (Venu) [mailto:venubabu@agere.com] Sent: Wednesday, February 08, 2006 1:51 AM To: Muranyi, Arpad Cc: Kotikalapudi, Shiva Kumar (Shiva); Patel, Nirav (Nirav) Subject: RE: [IBIS-Users] RE: [IBIS] To capture the delay variation with change in IO voltage Arpad, It is good to know that IBIS forum is actively working on these features. Thank you very much for the very detailed response and pointers. Best Regards, Venu -----Original Message----- From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Muranyi, Arpad Sent: Tuesday, February 07, 2006 11:16 PM To: ibis-users@eda.org; ibis@eda.org Subject: RE: [IBIS-Users] RE: [IBIS] To capture the delay variation with change in IO voltage Venu, The IBIS model will only partially for the Vcc variations. Here is how: If you lower the supply voltage, the origin of the pullup IV curve will go down to that lower voltage. So the pullup will pull up to a lower voltage. However, in real transistor circuits, this lower supply voltage would also reduce the IV curve size, because the Vgs voltage is smaller than at the normal supply voltage. This effect is usually called the "gate modulation effect" and is not reproduced by IBIS simulators to my knowledge. We are working on BIRD98 to describe this effect for IBIS models. http://www.vhdl.org/pub/ibis/birds/bird98.txt There may be two reasons for being interested in supply voltage variations. 1) Static DC characteristics of the buffer, i.e. how much will its strength change if we change the supply voltage. If you need this, you can generate several IV curves at different supply voltages and make a [Model] for each set. You can then use the [Model Selector] keyword to allow the tool to select the one you want to simulate with. 2) Dynamic noise simulations, i.e. you want to find out how the buffer will "degrade" its switching performance when there is noise in the supply voltage during its switching. This is a more difficult task, and IBIS is not doing too well on it. We have BIRD95 and BIRD98 as Lynne mentioned it already to solve this deficiency in the IBIS world. However, as usual, if you write your own models in the *-AMS languages, you can describe these behaviors to your heart's content without having to wait for BIRD95 and BIRD98. I hope this will shed some light on your questions. Arpad ========================================================= |------------------------------------------------------------------ |For help or to subscribe/unsubscribe, email majordomo@eda.org |with just the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or email a written request to ibis-request@eda.org. | |IBIS reflector archives exist under: | | http://www.eda.org/pub/ibis/email_archive/ Recent | http://www.eda.org/pub/ibis/users_archive/ Recent | http://www.eda.org/pub/ibis/email/ E-mail since 1993Received on Fri Feb 10 08:36:49 2006
This archive was generated by hypermail 2.1.8 : Fri Feb 10 2006 - 08:38:39 PST