How do you enhance your circuit design reliability?

Redundancy doesn't always mean higher reliability! It always depends on the failure mode you want to protect against. Example: 2 switches in parallel Failure mode "switch is shorted" => you have doubled the probability of an error! Failure mode "switch is broken open" => the second switch still can keep the system functional. Before implementing redundancy think about the probabilities of different error modes. Redundancy can REDUCE system availability!

Most companies won't spend the time/money for this unless it's going into a mission-critical application. The best bet is to have flexible FPGA-based implementations so that you can patch things in SW as you find issues.

You should also consider what I call cascaded failures. One common example is a power supply circuit where the electrolytic capacitors degrade over time, which then requires the driver diodes and/or FETs to pump more current into the circuit on each cycle to compensate. These parts eventually overheat due to the extra work and then end up failing, possibly damaging other components as they might fail shorted.

Reconfiguration (for instance using FPGAs) relies on non volatile memories. The cells of NVMs are very sensitive to radiation and to extreme heat (above 125°C). Radiation statistically erases singe cells. (consider multiple check sums to allow single bit error correction) High temperature typically reduces data retention time of the whole memory. (Rule of thumb: 6K temperature increase half the data retention time)

Some fault tolerance mechanisms are rather simple to implement and very effective. Understanding how an ESD discharge may impact your system and designing protective measures, such as diodes, to resist it is an example. When considering power supplies, a temperature de-rating, which reduces the delivered power if maximum temperature is achieved, it another type of fault tolerance mechanism which may prevent irreversible damage to the circuit.

In my experience, you spend lots of time guessing what might happen when your device is in the field. And you design test cases for the most obvious situations (ESD , over/under voltage). However, when it comes to the real world, it's all about design iterations. After you get a few thousand RMA's you realize you needed extra reverse current shunting, or that a gasket doesn't actually seal and you get egress at a certain location. What really helps is a very good sustaining engineering team, that has top-notch engineers and technicians that are capable of debugging what's happening and charting that data to find the corrective actions for the next revisions.

While designing a circuit we must look into key functional areas or where we could see more stress. We need to test the circuit at different elevated temperature to know when or what is going to fail . It can be noted from such DOEs which replicate field scenarios give the best reliability findings

Enhancing circuit design reliability involves rigorous testing, careful component selection, and consideration of potential failure points. Thoroughly simulate and test the circuit under various conditions to identify and address weaknesses. Choose components with proven reliability and adhere to specified operating conditions. Incorporate redundancy where critical, such as dual power supplies or backup circuits. Implement robust error-handling mechanisms and protection features to prevent damage from unexpected events. Additionally, follow best practices for layout and thermal management to ensure stable performance over time. Regularly update designs based on feedback and emerging technologies to stay current with industry standards.

Some companies still do not even simulate circuits. Today every circuit should be simulated for a few different reasons. One is to ensure you meet the requirements, another is for fault analysis and effect of component variance and another is so you have a quick basis for future designs that are similar but with new requirements. It can cut down on future design time significantly. This takes up front time commitment that management is sometimes unwilling to do but it is an investment in the future of the company. Design failure mode and effect analysis (DFMEA) Mean time before failure analysis (MTBF)

You can also increase reliability by making deliberate design choices which do not immediately impact performance but do impact long-term degradation. Deliberately limiting current peaks (e.g. on FET Drivers, on ESD discharges), among other choices, do result on a circuit that is more reliable than others.