---------- X-Sun-Data-Type: text X-Sun-Data-Description: text X-Sun-Data-Name: text X-Sun-Charset: us-ascii X-Sun-Content-Lines: 58 Hi, I guess, this is what the spec says about how to place data. MIN means minimum capacitance (not the fastest waveform), etc. It is up to the simulator to know how to use the data. For example, if you specify parameter FAST in a simulator, it will take the value MIN for C_comp. Simulator's manuals should mention this. Nikolai Bannnov Avanti Corporation :-) From owner-ibis@server.eda.org Tue Feb 15 15:18 PST 2000 :-) From: "Steve Constable" :-) To: :-) Subject: C_comp confusion :-) Date: Tue, 15 Feb 2000 17:30:27 -0500 :-) MIME-Version: 1.0 :-) X-Priority: 3 :-) X-MSMail-Priority: Normal :-) X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6600 :-) :-) I'm confused about C_comp. All of the data tables in an IBIS file are ordered as TYP, MIN then MAX. :-) But it looks like C_comp is ordered as TYP, MAX then MIN....that's were the confusion is. :-) The reason I think C_comp is ordered differently is that the MAX should have the smallest capacitance associated with it _not_ the greatest. In the example below (taken from the 21152_aa.ibs model from Intel), the C_comp has a max value of 0.50pF, this will slow down the I/O buffer (compared to the TYP case of 0.40pF), this contradicts what the rest of the model is trying achieve when the simulator is referring to the MAX columns (i.e. MAXimize speed). :-) Likewise I think the C_comp_min should be 0.50pF NOT what the model indicates as 0.30pF. :-) And the C_comp_max should be 0.30pF NOT 0.50pF as the model indicates. :-) :-) Just in case I've not made myself all that clear....below I have added a line to the original C_comp line: :-) :-) | TYP MIN MAX :-) [Temperature Range] 25.00 100.00 0.000 :-) [Voltage Range] 3.30V 3.00V 3.60V :-) C_comp 0.40pF 0.30pF 0.50pF :-) | should be: C_comp 0.40pF 0.50pF 0.30pF :-) I.E swap the 0.30pF with the 0.50pF...... :-) :-) I've checked with several different models and they all seem to have C_comp as TYP,MAX,MIN :-) Even the IBIS spec has the MAX value as the largest and not the smallest capacitance...as below: :-) Vref = 0 |Timing specification test load voltage :-) | variable typ min max :-) C_comp 12.0pF 10.0pF 15.0pF :-) :-) :-) If that's the way the spec has it, then I guess everyone will follow the spec, but I'm still confused as to why the MAX parameter has the largest capacitance when the objective of using MAX is to get the fastest switching time possible..... :-) :-) Any ideas or suggestions....????? :-) :-) :-) Steve Constable :-) Tundra Semiconductor :-) :-) :-) :-) :-) ---------- X-Sun-Data-Type: html X-Sun-Encoding-Info: quoted-printable X-Sun-Content-Lines: 125

I'm confused about C_comp. All of the = data tables=20 in an IBIS file are ordered as TYP, MIN then MAX.

But it looks like C_comp is ordered as = TYP, MAX=20 then MIN....that's were the confusion is.

The reason I think C_comp is ordered = differently is=20 that the MAX should have the smallest capacitance associated with it = _not_ the=20 greatest. In the example below (taken from the 21152_aa.ibs model from = Intel),=20 the C_comp has a max value of 0.50pF, this will slow down the I/O = buffer=20 (compared to the TYP case of 0.40pF), this contradicts what the rest of = the=20 model is trying achieve when the simulator is referring to the MAX = columns=20 (i.e. MAXimize speed).

Likewise I think the C_comp_min should = be 0.50pF=20 NOT what the model indicates as 0.30pF.

And the C_comp_max should be 0.30pF NOT = 0.50pF as=20 the model indicates.

Just in case I've not made myself all = that=20 clear....below I have added a line to the original C_comp=20 line:

| &nb= sp; &nbs= p; =20 TYP =20 MIN = MAX

[Temperature=20 Range]      25.00    &n= bsp;    100.00      &nb= sp; 0.000
[Voltage=20 Range]           &= nbsp; 3.30V         3.0= 0V        3.60V
C_comp         &nbs= p;            = ; =20 0.40pF       0.30pF   &= nbsp;   0.50pF

| should be: C_comp 0.40pF &nbs= p; 0.50pF = ;=20 0.30pF

I.E=20 swap the 0.30pF with the 0.50pF......

I've checked with several different models and they all seem to = have=20 C_comp as TYP,MAX,MIN

Even the IBIS spec has the MAX value as the largest and not the = smallest=20 capacitance...as below:

Vref =3D=20 0            =       =20 |Timing specification test load voltage
|=20 variable     =20 typ           &nbs= p;=20 min           &nbs= p;=20 max
C_comp     =20 12.0pF      =20 10.0pF        15.0pF

If that's the way the spec has it, then I guess = everyone will=20 follow the spec, but I'm still confused as to why the MAX=20 parameter has the largest capacitance when the objective of using = MAX is to=20 get the fastest switching time possible.....

Any ideas = or=20 suggestions....?????

Steve=20 Constable

Tundra=20 Semiconductor

&nbs= p; = ;

=20