A System and Method to Determine Soak Time

In a competitive engineering business world, there is a constant demand to meet stringent emissions and on board diagnostic (OBD) regulations in a cost-effective manner. Engineers are tasked with the responsibility to innovate and design solutions around cost-cutting measures that involve reducing bill of material costs on the printed circuit board (PCB). Varied features in commercial application specific integrated circuits (ASIC) devices makes it more challenging to create consistent engineering design methods to provide critical inputs for controls and diagnostic strategies. In addition, continuous evolution of the emissions and OBD regulations in the different markets make it challenging for ASIC design manufacturers to evolve their hardware designs quickly. One such input is soak time. Soak time is typically defined as the amount of time the engine has been turned off. Emission controls and OBD algorithms use soak time to enable cold and hot start processing strategies. There are many methods and patents that describe how soak time can be measured. Typically time is measured from the registers of an ASIC power supply hardware through a low power counter. However, some commercial ASIC’s do not provide the capability of reading time from the registers of a power supply. This may be due to an error in the silicon preventing the registers from being read. The proposal described here lays out an algorithm that leverages existing features in an ASIC to calculate soak time in the event time cannot be measured. Engineering tradeoffs will be discussed, coupled with downstream controls and diagnostic input strategy changes that would be required to accommodate this method of calculation. An example of a customer application with supporting data for a diagnostic function will be provided to show evidence of technical feasibility.