STMicroelectronics
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When an IC is no longer available, most people start by asking:
“What is the replacement part?”
This guide walks you through a practical five-step process for replacing a discontinued IC.
You may not need to redesign your product right away just because an IC is obsolete.
There are four common paths:
| Product has a short remaining life and genuine stock is available | Source and qualify the original part |
| A validated pin-compatible alternative exists | Use a drop-in replacement after testing |
| A functional alternative exists but needs PCB or firmware changes | Perform a controlled redesign |
| The device is highly specialized, custom, or unavailable | Consider functional-block redesign, emulation, or system retirement |
Don’t rush into a redesign just because the original part is obsolete. Also, avoid making a big Last-Time Buy just because redesigning seems hard.
Before searching for alternatives, confirm that the original component is actually discontinued and identify its complete ordering code.
Do not rely on a partial part number.
For example, a suffix can change the package, tape-and-reel format, temperature range, lead finish, memory setup, or automotive qualification. These differences can make a part that looks similar actually unsuitable.
Make a one-page summary of the original device before you ask suppliers or engineers to look at alternatives.
Use the following questions to decide whether to source the original part or replace it.
Require lot-specific photos, package confirmation, date-code information, condition confirmation, and inspection or testing appropriate to the application. For high-risk parts, use quarantine and incoming inspection before production release.
A pin-compatible alternative can save time on redesign, but being pin-compatible does not always mean it is safe to use as a direct replacement.
If the replacement needs different pull-up resistors, compensation capacitors, boot settings, or firmware changes, it is not a true drop-in replacement. It might still work well, but you should treat it as a design change.
A careful redesign should include an engineering review, a PCB update, a firmware review, sample testing, a compliance check, and procurement approval.
Some obsolete ASICs, legacy processors, custom interface devices, and mixed-signal ICs have no practical off-the-shelf replacement.
This option has the greatest impact on engineering, but it can also provide the best long-term supply stability for critical systems.
Just looking at the first page of a datasheet is not enough.
Build a side-by-side comparison table for the original part and each candidate.
| Package | Body size, pitch, pin 1 position, exposed pad | Prevents PCB and assembly mismatch |
| Pinout | Every pin function, no-connect pins, test pins | A matching package can still have a different pin map |
| Power | Supply range, sequencing, quiescent current | Prevents startup or power-rail failures |
| Inputs/outputs | Logic thresholds, drive strength, pull-ups | Prevents communication or control errors |
| Timing | Clock limits, propagation delay, reset timing | Critical for digital and interface ICs |
| Analog behavior | Offset, gain, noise, bandwidth, stability | Critical for op-amps, ADCs, regulators, sensors |
| Thermal | Power dissipation, thermal resistance, derating | Prevents field failures at high load |
| Protection | ESD, reverse polarity, fault behavior | May affect robustness and certification |
| Firmware | Registers, boot mode, drivers, calibration | Determines whether software changes are required |
| Qualification | Temperature grade, AEC status, reliability data | Required for regulated or harsh environments |
For power ICs, review the recommended external circuit, layout guidance, compensation network, switching frequency, thermal pad, and protection behavior.
For microcontrollers and programmable devices, review flash size, RAM, peripherals, boot mode, clock source, debug interface, pin multiplexing, and firmware migration effort.
For analog parts, compare how they work at the actual operating voltage and temperature, not just at typical room temperature.
Even if an alternative is technically perfect, it is not a good choice if it is almost obsolete, hard to obtain, available from only one source, or not offered in the package you need.
At this stage, engineering and procurement teams need to work closely together.
Engineering should not approve a part just because it fits electrically, and procurement should not approve a part just because it is available right now.
The replacement you choose should work technically and be reliable to source.
Make sure the replacement passes all the tests required for your product’s risk level.
For critical products, add reliability, environmental, EMC, software regression, and customer approval steps as needed.
For automotive applications, matching the package and electrical parameters is not sufficient.
Any alternative part still needs to be checked against your product’s engineering, customer, and quality requirements.
| Hardware engineer | Electrical comparison, circuit impact, test definition |
| Firmware engineer | Register, boot, driver, and software compatibility |
| Procurement | Availability, lead time, supplier options, price, MOQ |
| Supply-chain manager | Lifecycle monitoring, risk score, continuity plan |
| Quality team | Traceability, inspection plan, incoming controls |
| Program manager | Timeline, cost, customer impact, approval gates |
Replacement projects often fail when only one team handles everything.
A buyer might find stock that engineering cannot approve, or an engineer might pick a good alternative that procurement cannot get reliably. The replacement plan needs to bring both sides together.
This approach changes an urgent sourcing problem into a well-managed project.
Welllinkchips supports sourcing of obsolete, hard-to-find, and long-lead electronic components.
A clear request makes it easier to decide if you need qualified original stock, a practical alternative, or a long-term redesign.
No. Some manufacturers provide a recommended successor, but many obsolete ICs have no drop-in replacement. Every candidate must be checked for compatibility with the package, pinout, electrical, functional, firmware, and qualification requirements.
No. Pin compatibility only confirms part of the requirement. The candidate should still be reviewed and tested in the real circuit and operating environment.
It depends on remaining product life, demand, redesign cost, inventory risk, and the availability of a validated alternative. Often the right strategy combines short-term qualified inventory with a long-term redesign.
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