What Is EOL? Dealing With NRND and Obsolete Parts
Whether a design can be produced for years depends not only on good engineering but also on the lifecycle of the parts it uses. A component that's abundant today can go out of production within a few years and force you into a mandatory redesign. In this article we cover the concepts of EOL, NRND and obsolete, and how to manage this risk.
Lifecycle states
Components pass through different states over their production lifecycle:
| State | Meaning |
|---|---|
| Active | In active production, recommended for new designs |
| NRND | Not Recommended for New Designs; still produced but with an uncertain future |
| EOL | End of production announced; the last-buy period has begun |
| Obsolete | No longer produced; found only from remaining stock |
Why is EOL risky?
A part going out of production can suddenly become unavailable; as remaining stock runs out, prices spike and counterfeit risk rises. Worst of all, a critical part becoming obsolete can require redesigning the entire product — a loss of both cost and time. That's why EOL is one of a design's hidden but most expensive risks.
EOL notice and last-time buy
When manufacturers discontinue a part, they usually publish a notice (PCN/PDN – Product/Process Change Notification). This notice includes the last-order and last-delivery dates. A bulk purchase made during this window is called a last-time buy (LTB): it's the final chance to calculate and stock your remaining need in advance.
How do you manage the risk?
- Early detection: flag NRND/EOL parts in the design from the start; avoid surprises.
- Multi-source selection: where possible, prefer parts available from multiple manufacturers with a second source.
- Equivalent plan: identify an alternative for critical parts in advance.
- BOM scanning: regularly check your bill of materials for lifecycle status.
On PartAndStock, you can upload your bill of materials to the BOM tool to see risky items in bulk, and plan an alternative for each with the cross-reference tool.
Frequently asked questions
Can I keep using an NRND part?
It can be used in your current production, but it's not recommended for new designs because it may go EOL soon. Plan its alternative where possible.
How do I determine the last-time buy (LTB) quantity?
You estimate your total expected need over the product's remaining production life and add a safety margin; you balance excess-stock cost against the risk of running out.
Does an obsolete part always have an equivalent?
Not always. Some old parts may not have an exact equivalent; in that case a circuit redesign may be needed. That's why managing the risk early matters.
Conclusion
EOL risk, left unmanaged, is one of the most expensive surprises; but with early detection, multi-source selection and a ready equivalent plan, it can be brought largely under control. To see your design's lifecycle health, start with the BOM tool.