Functional modelling is the activity of defining a device in terms of its function or behaviour rather than specifying a device model name for which a model exists. Functional modelling has a number of uses. Here are two examples:
System level simulation.
You are investigating the viability or characteristics of a complete system before actually considering its implementation detail. Your system may consist of a number of interconnected blocks each with an easily defined function.
Device model implementation.
Functional models can be used to actually create device models. Suppose you wish to use an op-amp for which no model is available. The only characteristic that affects the performance of your circuit is its gain bandwidth product. So instead of creating a detailed model you simply use a differential voltage amplifier with the appropriate GBW.
Pulsonix provides functional modelling at both the schematic and simulator levels. The schematic provides a convenient user interface to the functional devices provided by the simulator. This is accessed via the Digital Generic and Analog Behavioural pop-up toolbars.
The simulator provides three devices that can be defined in a completely arbitrary manner. These are:
Arbitrary non-linear source or “B” device
Analog non-linear device. Can express single voltage or current in terms of any number of circuit voltages and currents including its own output.
S-domain Transfer Function Block
Linear block with single input and output each of which may be single ended or differential, voltage or current. Specified in terms of its S-domain or Laplace transfer function.
Arbitrary Logic Block
Digital device. Implements any digital device, combinational, synchronous or asynchronous using a descriptive language.
In addition, the simulator also provides a generic digital to analog converter and a generic analog to digital converter for converting between the analog and digital domains.
Use the Simulator’s Device Reference Manual pages accessed from the Simulator Command Shell menus to find out more detail about these functional blocks.
Much of the functionality of the above mentioned simulator devices is supported by the schematic editor with a convenient user interface. For details, refer to the device section below.
Functional Devices Provided in Pulsonix Schematics
Non-Linear Transfer Function
Based on the arbitrary non-linear source. This will choose a schematic symbol with your specified inputs and outputs. You enter the equation to relate them.
Laplace Transfer Function
Based on the S-domain transfer function block. This will choose a schematic symbol with specified input and output. You enter an S-domain transfer function.
Arbitrary non-linear passive devices
Non-linear passive components based on non-linear source. You enter component value in terms of its voltage (R and C) or current (L).
Arbitrary Non-Linear Capacitor
Generic ADCs and DACs
Generic ADC and DAC with user specified resolution, range, offset and timings.
Generic digital devices
Generic digital devices. All have user specified data path sizes and timings.