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Layout example of dual-footprint TPS7A02 SOT-23 and X2SON packages (Source: Texas Instruments)
Reducing supply chain risk is typically a low priority when starting a new project. Device procurement often takes a back seat to goals such as the implementation of a new feature, improving circuit accuracy, precision, or increasing battery life.
But with some creativity and forward thinking, minimizing supply chain risk is possible during device selection, and when working on schematics and layout before generating a final bill of materials (BOM). By selecting components in packages that work in a dual-footprint layout, you can add more flexibility to the supply chain and reduce risk by increasing the number of devices that can be used in a given circuit design.
Selecting a dual-footprint device
While this concept applies to many different types of devices and device packages, in this article I will explore the dual-footprint concept leveraging a low-dropout linear regulator (LDO) in small-outline transistor (SOT-23) and extra-small outline no-lead (X2SON) packages. Because the X2SON is small enough to fit inside the SOT-23 footprint, you can double the number of components supported by the same printed circuit board (PCB) layout without increasing the design’s physical size.
Multiple other packages could work in a dual layout without taking up more board space. However, if there is plenty of space on the PCB, it is always possible to put the two footprints side-by-side rather than placing them on top of each other.
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