# Circuit Simulation & Automated Electrical Stress Analysis

BQR’s electrical stress analysis software includes two modules: Rapid and Precise.

Rapid: Logical stress calculations for an incomplete design.

Precise: A unique circuit simulator for detailed stress analysis (Power, Voltage and Current) of a complete design.

### Rapid Stress Simulation

fiXtress Rapid performs automated calculation for incomplete design in the Schematics Phase, using logical calculations, enabling multiple engineers to work concurrently on a single design. This analysis helps select the appropriate component rating before the final BOM freeze.

The schematic design represented by the BOM and Netlist is used to calculate the Electrical stress of the components. The ground signals specification and ICD data are also needed to set power input constraints. These calculations use data from the Components Database, which includes the components’ electrical properties from the datasheet. The data is used to calculate DC operational parameters, such as power dissipation, voltage and current. Results are then provided to the Stress Derating Analysis module.

### Precise Stress Simulation

fiXtress Precise performs automated Stress Analysis for complete design in the verification (pre-layout) phase, using a circuit simulator. Accurate stress calculations are performed after the BOM freeze, providing actual operational parameters for all components in the circuit, such as power dissipation, voltage and current for a mixed signal, Analog, Digital, and RF including DC/DC power supplies.
fiXtress Precise uses State Vectors for analog circuits, and Bus-Simulation for digital circuits. The results serve as guidance for smart component placement based on component power dissipation.
The electrical stress calculation on all the design components using Kirchhoff loops and Fourier Analysis. The calculation includes tens of parameters according to the component type. The calculation will be performed only on the finished product design and will check the components stress against their maximum and derated ratings at the operating temperature and also adds thermal considerations to the layout phase.

Example:

Electrical parametric rules checks
The following type of error is very difficult to detect during integration and final tests, and even by a massive Root Cause Analysis (RCA).
Mostly the analyst will blame the software, since nothing is burned but the product is not functioning correctly.

Transistor Q1 provides digital input to pin 40 of U1. It should be above 2.3V for “1” logic, and below 1.0V for “0” logic.

But Q1 provide 1.052V, which U1 will, one time understand as “1” and one time as “0”, which will make the functioning not stable.

### fiXtress Generates Electrical Stress data for Thermal Analysis

One of the most important parameters for thermal analysis is the actual power dissipated in each component. This power is calculated automatically by fiXtress circuit simulator and can be provided to the thermal analysis tool. Usually, this parameter is unavailable to the thermal engineer and that is why he uses the maximum value of the components power from the datasheet. In this case, these results are the worst case and if we use them we will create over-design such as over-cooling or taking components with higher rating values (which may be desirable), but sometimes it increases the cost and the physical size of the product unnecessarily.

### fiXtress Generates Electrical Stress data for Reliability Physics (Physics of Failure) Predictions

The product Reliability is measured by the MTBF according to different standards or by the Failure Rate distribution in time using the Physics of Failures method. These calculations are strongly influenced by the stress of each component. In this case, fiXtress provides the exact stress and consequently the reliability calculation is more accurate.