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Cadence IC5.1.41 Current probing

ag2888

Hi,

 I have a query wrt the probing currents in cadence.

To probe the current i click on the pin (device or Instance symbol) , which shows a circle around it. The problem that i am facing is that this works perfectly when my simulator is Spectre.

But when my simulator is hspice probing a device pin gives a warning :

 Element xpm1 in print, plot, probe or measure statements is invalid. Output is ignored.

And the currents are not plotted.

I am trying to probe the drain currents of PMOS in a simple current mirror circuit.

When i check the netlist created for hspice, there exists a definition for xpm1 and the probe statement for it is I1(xpm1). For the same simulation i am able to plot the transient node voltages as well current at the plus terminal of an ideal current source or a instance symbol pin.

 

Another difference that i noticed between the two input files (.scs and .ckt) is that:

In input.ckt (hspice) : the devices are defined as XPM or XNM instead of MPM or MNM

In input.scs (spectre) : the devices are defined as PM or NM.

The model files for both spectre and hspice contain the definition of mosfets as subckt.. 

 

Could anyone please suggest what could be the reason for this? 

  • Spectre doesn't use the initial character of the instance name to determine the type of the component; it simply uses the name of the thing instantiated and that can be a subckt, a veriloga model, a model or a built-in primitive - the syntax is the same. With HSPICE (like other SPICE simulators), the initial character determines whether it is a mosfet (M), a bipolar (Q), resistor (R) or subckt (X) amongst others. So it has to be netlisted differently for hspice than for spectre.

    That said, I'm not sure the syntax for measuring the terminal current for a subckt instance in HSPICE. Whatever it is, it's controlled via the termMapping in the hspiceD simulation information in the CDF for the component in question.

    You probably should talk to whoever provided the PDK; maybe something needs fixing?

    Regards,

    Andrew.

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