In a normal operating lifetime for mission-critical applications such as automotive, one of the major reasons for failure is due to thermal overstress. With many of these mission-critical applications employing devices that drive actuators at high power, thus increasing the temperature, the stress of operating at a high temperature for prolonged periods can cause that device to fail well before its operating lifetime should allow.
Multiple challenges must be addressed for accurate thermal simulation for mission-critical applications, two of which are related to thermal shut-down circuitry: thermal sensor placement and the sensing delay. Within this scenario, the sensor is typically placed a distance away from the hot spot and thus provides an inaccurate reading of the actual temperature, therefore contributing to early failure.
The Cadence® Legato™ Reliability Solution takes a different approach for thermal analysis compared to the self-heating effect (SHE) approach built into some device models and other self-heating-based thermal simulation approaches, because self-heating doesn’t consider thermal interactions between devices. The solution’s electrothermal simulation provides multiple modes of simulation operation, including steady-state thermal analysis for reliability analysis, direct state for signoff dynamic thermal analysis, and co-simulation for fast, high-capacity dynamic thermal analysis. It considers all the power sources on a whole chip, including transistors, resistors, and other devices, thus enabling designers to simulate the effect of device self-heating and mutual heating effects on adjacent devices on the chip. And because the electrothermal simulation is integrated into Spectre® APS transient analysis, it allows designers to easily assess the effect of on-die temperature variation on circuit performance.