[Sorry, resend] Hi, Arpad, Thank you for your fruitful comments. Current mode current stealing is widely employed in clock gen. technology for Intel, such as CK409, CK410 etc.. We performed the simulation works by using SPECCTRAQuest and Hspice as well. The models are all in IBIS file format in v3.2. These two famous simulation tools presented almost the same results. The most interesting is the discrepancy qualitatively between simulation and measurement and/or prediction theoretically. Theoretically, the parallel termination resistors shall be placed close to the driver as possible for current mode current stealing technology and close to the end of receiver for voltage mode to eliminate the reflection. However, the simulation results did not indicate this trend for current mode current stealing buffer. That is said, we also need to place the termination resistor close to the end of receiver to get good signal integrity. Obviously, this is not meeting the trend of measurement and theoretical prediction. As I said in the previous message, this trend can be exactly predicted if we create an equivalent buffer model in spice format. We are unable to ensure the root cause of this discrepancy. It may be the limitation of IBIS v3.2 as Lynne said, or the solver=A1=A6s issue. For us, we can only get the model from chip vendor. We hope we can make some modifications on IBIS files and/or simulation set-up to obtain accurate simulation results on this issue. Thanks for any Guru can share his/her experience. Best Regards, Sogo Hsu, Ph. D. Simulation center/PCEG/Foxconn Electronic --- In si-list@xxxxxxxxxxxxxxx, "Muranyi, Arpad" <arpad.muranyi@xxxx> wrote: > Sogo, > > I am not sure what "current mode current stealing" is, but > to respond to the rest of your question I would like to say > that there must be another reason that makes your IBIS > simulation different from SPICE or measured. > > In terms of the IV curve of a device or its simulation there > is really no such thing as current or voltage mode. The shape > of the IV curve determines it all. If your IV curve is a > horizontal line, you have an ideal current source. If your > IV curve is a vertical line, you have an ideal voltage source. > If your IV curve is a diagonal line of some slope, you have > a linear resistor, and finally if you have a curved IV curve > you have a (non linear) diode, transistor or some sort of a > device. There are no ifs and buts about this. You tool may > select current as a known and voltage as the unknown, or vice > versa, but the model is still the same IV curve. > > If there are discrepancies between your SPICE and IBIS models > that means that either the IV curves are not the same, or there > are perhaps other elements (or behaviors) in the SPICE model > which are not described by the IV and Vt curves of your IBIS > model. If there are features in the buffer which are fancy > (dynamic) effects that IBIS 3.2 cannot describe with its > relatively simple IV and Vt curve approach, you may need > to resort to *-AMS as your modeling language as Lynne > suggested. But this would not fall into the definition > of "current mode" vs. "voltage mode". > > I hope this helps, > > Arpad Muranyi > Intel Corporation > =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D =3D3D=3D3D=3D > =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D =3D3D=3D3D=3D > =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D > > > -----Original Message----- > From: si-list-bounce@xxxx > [mailto:si-list-bounce@xxxx]On Behalf Of Sogo Hsu > Sent: Wednesday, February 25, 2004 12:11 AM > To: si-list@xxxx > Subject: [SI-LIST] Current mode current stealing simulation by IBIS file > > > Hi, Gurus, > > A question regarding current mode current stealing circuit=3D20 > simulation confused me for a long time. The simulation results=3D20 > totally different from the measured as well. To understand the cause=3D20 > of discrepancy, I tried to set up two kinds of circuit, one is=3D20 > voltage mode and the other one is current mode. In general, IBIS=3D20 > file describe the v/t curves of I/O cell with test feature. We can=3D20 > easily generate the same v/t curve for these two. However, the Spice=3D20 > simulation indicated the results are totally different if the whole=3D20 > link is under considered. The behavior of current mode spice model=3D20 > is similar with the measured. In my opinion, this phenomenon can be=3D20 > analog to TE and TM mode. Therefore, the refection condition is=3D20 > definitely different even they have owned same v/t curve in IBIS=3D20 > file. My question is, how we overcome this issue if we only use IBIS=3D20 > file for simulation. In general, we can only get IBIS files from=3D20 > vendors.=3D20 > Can any expert on this topic share the experience to me? Thank you=3D20 > in advance. > > Best regards, > > Sogo Hsu, Ph. D. > Simulation center/PCEG/Foxconn Electronic > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxx with 'help' in the Subject field > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: =3D20 > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > =3D20 > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxx with 'help' in the Subject field > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu