1. Define What the Purchase Must Cover

Start with the product or service obligation the component must support. A lifetime buy may cover the remaining production programme, repair needs for an installed base, or a transition until a replacement is qualified. These are different demand streams. Define which belong in the purchase and when each ends, rather than assuming that a product's sales forecast captures all future component consumption.

Distinguish the planning decision from the manufacturer's last-time-buy status. TI describes last time buy as a product undergoing discontinuation. NXP distinguishes an EOL ordering window from the subsequent no-longer-manufactured status. Analog Devices identifies separate final ordering and shipment dates in its discontinuance information. These sources establish lifecycle boundaries; none supplies your company's required purchase quantity.

Use the complete ordering code, package and applicable revision. Record the formal notice and affected-model list, then confirm that your specific orderable item is included. A family-level lifecycle label is a starting point, not proof that every suffix shares the same deadline or replacement. This guide concerns quantity planning; the individual notice determines the applicable purchasing window.

  • Name the products, repairs and approved transition covered by the purchase.
  • Set a dated coverage period and a responsible demand owner.
  • Match the exact ordering code to the manufacturer's current notice.

2. Build Demand and Inventory Inputs

Convert expected finished-product builds into component units using the approved bill of materials. Add separately justified service consumption and any documented process allowance. Avoid counting a spare twice, such as once within repair demand and again within a blanket safety factor. Every additional allowance needs an explanation, an owner and the period it protects.

For uncertain demand, keep lower, working and higher scenarios visible instead of hiding uncertainty inside one precise-looking number. Consider approved programme changes, the timing of a qualified replacement and customer support obligations. State which assumptions would change the result. Do not apply a universal buffer percentage or turn an unconfirmed sales opportunity into committed production demand.

Count only stock usable for the specified requirement. Separate quarantine, damaged packing, engineering-only samples, inventory reserved for other programmes and material awaiting acceptance. Confirm the available quantity and supporting records with the inventory owner. For inbound supply, record the exact item, committed quantity and arrival expectation; exclude duplicated, conditional or unallocated offers. Availability must align with when the demand occurs.

  • Use component units throughout, with clearly defined forecast periods.
  • Reconcile physical stock, reservations and accepted inbound commitments.
  • Show uncertainty and exclusions as separate planning fields.

3. Calculate and Test the Net Requirement

Use this working framework: net planning quantity = maximum of zero and [coverage demand + justified safety allowance − verified usable inventory − confirmed available inbound supply]. It is an ICULTRA planning aid, not a manufacturer formula or a supply assurance. Calculate every term for the same exact part, unit of measure and coverage period. Keep the supporting demand and inventory worksheets with the result.

If the result is negative, the arithmetic quantity is zero; review assumptions rather than creating a negative purchase. Next apply only confirmed minimum-order, lot-size or packaging constraints. Record any required rounding and the extra inventory it creates. Do not invent a minimum order or automatically round to a convenient reel size when the supplier has not confirmed that condition.

A total quantity also needs a time check. Map scheduled receipts and expected consumption to find a shortfall before inbound material arrives. If delivery is uncertain, show that dependency instead of silently treating the stock as available today. Review the demand scenarios with engineering, purchasing and finance before choosing an approved quantity.

Assess storage independently of the equation. Ask the quality team to review manufacturer packaging, moisture-handling and applicable storage or drying guidance for the specific device and intended holding period. A quantity calculation cannot establish shelf life, solderability or future usability. If those constraints are unresolved, record them as conditions to resolve before commitment.

4. Document the Decision and Source the Exact Item

Keep an approval record with the forecast version, coverage dates, inventory reconciliation, uncertainty assumptions and final quantity. Attach the exact discontinuance notice and its revision. Analog Devices' lifecycle guidance identifies affected models, final order and shipment dates, and replacement information as notice fields. Record those separately from your internal calculation; a revised notice may change the purchasing opportunity without changing consumption.

Ask the manufacturer or its authorized channels about the applicable order conditions and availability before relying on a proposed purchase. If other sourcing routes require review, define the acceptable condition, traceability documents and inspection scope with your quality team. A listing or inquiry response does not reserve stock, establish authenticity or prove that the full calculated quantity is orderable.

Send the exact part number, documented net requirement, required arrival schedule and available notice through ICULTRA's sourcing inquiry route. State which facts are confirmed and which need investigation. A sourcing review can assess a defined request; it does not replace your lifetime-buy approval, engineering qualification or supplier-specific written offer.

Sources and further reading

Manufacturer documents support the technical guidance above. They do not confirm our stock, authorisation or the condition of any offered lot.