SIMPLIS Digital Devices

SIMPLIS has a comprehensive built-in library of digital models ranging from primitive gates to high-level macro models, such as a barrel shifter or multiplier. Using these digital models, a wide variety of digital circuits can be simulated. A typical application for these digital models is a digital control loop that controls a switch-mode power converter.

The video below is a demo of this circuit. A hierarchical example can be downloaded here: Digital_PWM.zip.

Note: Before downloading and unzipping the file, close any SIMetrix/SIMPLIS dialog boxes before simulating.

Regardless of the quantity of digital content, using SIMPLIS digital components is practical for virtual prototyping of mixed-mode analog and digital circuits in power conversion applications.

  • SIMPLIS allows designers of digitally controlled power supplies to effectively explore the interaction between increasingly complex digital control schemes and the resulting performance of the complete power supply system.
  • The SIMPLIS digital functions remove the need to build these functions up from the gate level, effectively reducing the circuit size and the complexity of the simulation.
  • SIMPLIS also improves the simulation speed of power supply systems with significant digital content describing supervisory and protection circuits.

The SIMPLIS Digital Library provides a variety of digital functions to simplify your simulation efforts. In addition to the basic logic gates that existed in early versions of SIMPLIS, the library now includes the following:

All of the above logic functions in the SIMPLIS digital library have these characteristics:

  • Inertial delay on inputs means that input glitches narrower than the specified delay are ignored rather than being propagated through the device.
  • Finite delay in all SIMPLIS digital devices eliminates problems associated with the ability of the classic SIMPLIS logic gate to instantaneously switch state with zero delay.

Simulation speed is improved 10 to 20 times for classic digital gate simulation compared to early versions of SIMPLIS. This improved speed in current SIMPLIS digital simulator allows the simulation of digital circuits to go faster and reduces the numerical complexity of the power supply simulation. For more information, see Maximizing Simulation Speed in Mixed-Mode Simulations.

Additionally, the digital clock frequency can now be much higher than the switching frequency of power supply. This allows SIMPLIS simulation times of power supplies with digital control schemes to be comparable to those with equivalent analog control circuits.

Most devices have the ability to use a Ground Ref pin. A Ground Ref pin is required whenever a digital device is connected to an analog component. For more information, see When is Ground Ref Required?

To understand how the SIMPLIS simulator arrives at the signal level of a circuit node that is connected to one or more digital devices, the user is suggested to read the Signal Level of a Node topic.

Starting with version 8.40, SIMPLIS supports the creation of user created DLL-defined Digital Devices written in C/C++.

  1. When is Ground Ref Required?
  2. Signal Level of a Node
  3. Maximizing Simulation Speed in Mixed-Mode Simulations
  4. SIMPLIS A to D / D to A
  5. SIMPLIS Counters
  6. SIMPLIS Discrete Time Filters
  7. SIMPLIS Flip-Flops
  8. Introduction to Digital Functions
  9. SIMPLIS Gates
  10. Introduction to SIMPLIS Registers
  11. Digital Sources
  12. DLL-defined Digital Devices
  13. Tri-State Buffers and Pull Up/Down Resistors