Non-Invasive Stability Measurement (NISM) is an alternative to Bode Plots and provides a better indication of control loop stability as it is based on stability margin. Performing NISM allows designers to assess stability without breaking the control loop which has a number of benefits both in simulation and testing. NISM Implementation in PSpice is ideal for circuits where a Bode plot assessment is not feasible due to insufficient access to the feedback loop such as:
- Voltage references
- Fixed voltage LDOs
- Integrated POLs
Performing a non-invasive stability measurement in PSpice is also ideal for circuits where the feedback loop is difficult to access, such as:
- Circuits where the hardware is integration
- Circuits that would require modification like cutting a PCB trace
This video will discuss how to implement a Non-Invasive Stability Measurement (NISM) in PSpice, including:
- How to modify your circuit to perform a non-invasive stability measurement
- Which Power IC models to use in your simulations
- How to plot power supply impedance
- Importance of analyzing the QTG curve or group delay waveform
- Using NISM measurement macro
For more information, view the NISM Manual from Picotest and upgrade your PSpice license here to start performing non-invasive stability measurements in your SPICE simulations.
