Experimental Implementation of 8.9Kgate Stress Monitor in 28nm MCU Along with Safety Software Library for IoT Device Maintenance

The on-chip stress monitor was experimentally implemented in a 28 nm automotive micro-controller-unit (MCU) to demonstrate the contribution to long-term fatigue monitoring of the MCU as well as short-term anomaly finding of the system. The monitor comprises of 8.1 Kgate digital soft-macro including four stress counters driven by 0.8 Kgate two dedicated ring oscillators, which automatically convert environmental temperature and voltage stress into oscillation frequency according to Arrhenius and Eyring models. The monitor operates independently in the background of main operations. The safety software library was developed to extract beneficial information from the counters after every power-on reset, including stress age and temporal variations of thermal stress. The functions were confirmed by the MCU measurements. The library also proved to contribute to functional safety of main temperature sensor. Future usage picture of the monitor was discussed including IoT maintenance, system design feedback and used electronics recycling.