[IBIS-Users] BIRD95 modeling suggestion

Hi everyone,

From Friday's conf call, it seems that there will be a number of issues
surrounding BIRD95. I would like to draw attention to one issue with the
suggested model. The schematic includes resistances and partial inductances
for power and ground. There are a few issues with this methodology. First,
there is no mutual inductance between the two - this is required for the
partials to be meaningful. Then, what physical location is selected for the
measurement of VDDQ's current such that the inductances and resistance are
accurately modeled in the extraction?

Do we expect the IBIS model builders to include a distributed PDS network in
their extractions? The schematic shows L and R going into the devices as a
whole, but there is no PDS model shown between the on-die cap, the
pre-driver, nor the final driver. I suspect this will be the typical
simulation setup, where all components are directly connected to the same
power and ground nodes, without a distributed on-die PDS model.

I recommend that we remove the resistances and partial inductances from the
schematic. This will further enforce the concept that the IBIS device is a
"black box" - the actual, physical location of the power and ground
connections are then clearly defined. Their connections to the rest of the
system are then unambiguous, and interconnect modeling remains in the final
simulator's domain.

I've included the schematic below for reference. Best regards,

Sam

|--------------------------------------------------------------------------
(**)
| |
<---
|
___________________________________________________________|___VDDQ
| | | | | | |

| | | | | | |

| ----- | | | | |

| | E | | / | | |

| | S | ---------------- \ P_| --- PowerClamp |

| | R | | Pre-Driver | / || / \ |

| ----- | Circuit | \ ||__ --- |

| | | powered by | | | | |

| | | VDDQ | | | | | I_sig |

| ----- ---------------- | | | | -------> |

| | E | |
o-----o--|----o------------------- I/O
| | S | | | | | | |

| | | L | | | | / | | | |

|I_bypass| ----- I_pre| |I_term| \ N_| v --- GNDClamp |

| | | | | | / || I_cb / \ |

| v | v | v \ ||_ --- |

| ----- | | | | |

| ----- C_p+b | | | | |

|
|___________________|_________|_____|_______|_______________|____GND
| |

| |

|-------------------------------------------------------------------------|
 

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Received on Mon, 10 Jan 2005 10:04:37 -0800