There are many reasons for shortages in the supply chain—too much demand and too little capacity, wafer shortages, global instability, weather events, and more.
For years, we've all known that implementing solutions with a minimum number of parts using highly reliable integrated circuits is the best design approach. Often ICs are used to implement functions such as ramp generators, differential amplifiers, oscillators, switches, or gate drivers. However, if it takes you more than 99 weeks to get your hands on an amazing proprietary IC, you may regret your decision. You can use discrete components and have an alternate source for less complex circuit functions. That way, if a supplier decides to stop producing components such as MMBT3604, 1N4148, or MMBT3906, there are plenty of other suppliers to choose from, and you can continue to produce. In addition, if you need a specific component in your design, you can use discrete components for that as well. At the same time, with integrated circuits, it is often the case that certain functional decisions have already been made for you and you cannot change them.
Of course, Specific Integrated Circuits meet part count and cost criteria, but perhaps a new design could include a dual layout to hedge against shortages that limit production. In this case, only one layout on the printed circuit board is populated and the other is not. If a component is out of stock, only the alternate layout is populated. This method is more expensive, but it's cheaper than not shipping for two years.
Electronic components suppliers have to figure out how to make their supply chains more robust, and customers seem to force them to fix the problem through supply chain meetings, surveys, and scorecards. The problem will be solved, but it will take time. Wafer fab facilities are expensive and take time to build.
Another challenge is that many suppliers are not committed to customer orders. When you've waited the initial 22 weeks for delivery and then realize the backlog is gone and the lead time suddenly becomes 99 weeks, that means the supplier sold your part to a more favored customer.
Imagine a proprietary integrated circuit that must be used is suddenly "End of life".
Figure 1. Example of a relay driver design where the part became EOL.
Figure 1 is a practical example of this problem. It shows a relay driver for an HVAC 75mA contactor. A single component was inserted into production to provide multiple types of protection; no external parts were required, yet it suddenly end of life.
Solution: Utilize Discrete Values
What to do now? Maybe change the design to use the discrete component that should have been used in the first place. How about 2N7002? Lots of people do it. How about adding some 1N4148 or 1N4004 and TVS components to provide protection. These discrete components are very familiar and well-tested discrete components.
Figure 2. Redesigned circuit design in Figure 1 using discretes.
Figure 2 shows the discrete design." Q1" is a 2N7002. "D1" and the anti-EMF diode for the relay coil can be a 1N4148 or 1N4004, and "D2" can be a BZT52B9V1-G, P4SMA9.1, or similar component." R1" can be about 100K ohms and "R2" can be 100 ohms depending on the logic switching signal applied to the "R2" input, which is only used to protect the gate of the 2N7002.
So when Specific ICs are in short supply, it may be a good idea to consider a discrete component to prevent "semiconductorization".
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