Existing-design power-device selection
How to Select an Infineon Power Device for an Existing Design
To select an Infineon power device for an existing design, first classify the request as a no-change replacement, controlled alternate or redesign. Then compare the exact ordering codes at the real voltage, current, temperature, switching, drive, package, cooling and protection conditions. Keep the candidate on hold until missing limits are measured and the intended hardware passes defined acceptance tests.
A lower on-resistance or matching voltage rating earns a place on the shortlist. It does not establish a drop-in replacement.
Mounted power MOSFET and surrounding PCB constraints
© Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons).
Start with the permitted change boundary
What kind of replacement is your project actually allowing?
Use the narrowest path that matches the approved project scope. The same candidate can be acceptable as part of a redesign and unacceptable as a drop-in replacement.
| Project condition | Recommended path | Evidence required | Stop boundary |
|---|---|---|---|
| No design changes | Evaluate a drop-in candidate. | Exact pinout and drawings, normalized electrical comparison, unchanged drive/cooling evidence and board-level validation. | Stop if any PCB, driver, firmware, cooling or assembly change is required. |
| Specific changes are allowed | Document a controlled alternate. | List every permitted change, responsible owner, affected revision and test result for the exact configuration. | Hold if the approved BOM cannot identify the device and required changes together. |
| Architecture can change | Run a redesign study. | Re-evaluate device technology, topology, gate drive, layout, cooling, protection and qualification. | Do not describe the result as a drop-in or unrestricted alternate. |
| Change scope is not agreed | Freeze the sourcing decision. | A shared constraint list approved by engineering, quality and purchasing. | Do not order the candidate as an equivalent while the boundary remains unclear. |
Swipe the table horizontally on smaller screens. The complete decision rules remain visible without an interactive selector.
01 / Freeze the baseline
Which existing-design constraints must the candidate survive?
Give engineering and purchasing the same starting document: the original manufacturer part number, full ordering code, circuit revision and allowed changes. A family name or package-top marking alone is not enough.
Which voltage and current stresses must be captured?
Record maximum supply or DC-link voltage, ripple, measured overshoot, reverse voltage, current RMS, peak current and overload duration. Include regeneration, startup and shutdown where relevant. There is no universal voltage-margin percentage that replaces this analysis.
How is the existing device switched?
Identify high-side or low-side duty, hard or soft switching, switching-frequency range, dead time and reverse-current path. An inrush limiter operating in its linear region needs a different safe-operating-area (SOA) review from a fully enhanced switch.
What must be recorded about the driver and protection?
Capture actual gate-voltage range, source/sink capability, separate turn-on/off resistance, isolation, Miller clamp and negative bias if used. Record overcurrent or desaturation thresholds, blanking time and the complete fault-response delay.
Which mechanical and thermal constraints are fixed?
Fix the land pattern, pin order, package height, electrical tab connection, heatsink interface, airflow and insulation arrangement. State maximum ambient or coolant temperature and the intended junction-temperature limit.
Which assembly and mission-profile conditions matter?
Include soldering process, moisture handling, mounting torque where specified, vibration and the real load cycle. A product that delivers brief peaks is not equivalent to one running at peak load continuously.
Which qualification and release limits must be defined?
List required automotive or industrial qualifications, customer approvals, safety/EMC requirements and the remaining production lifetime. Define acceptance criteria before comparing sample results.
02 / Shortlist by circuit function
Which Infineon family should you investigate?
Use the existing topology to narrow the search. These are starting points, not fixed voltage or frequency boundaries and not a substitute for the exact device datasheet.
| Family / device type | Useful starting point | What can stop a substitution? |
|---|---|---|
| OptiMOS / StrongIRFET | Silicon MOSFET stages in DC/DC converters, battery systems and motor drives. | Hot on-resistance, gate charge, diode commutation, avalanche conditions and package current path. |
| CoolMOS | High-voltage silicon superjunction MOSFETs in suitable AC/DC and DC/DC stages. | Output-capacitance behavior, reverse recovery, hard/soft-switching conditions and existing gate tuning. |
| CoolSiC | High-voltage switching where a SiC MOSFET's loss profile may improve the system. | Gate-voltage limits, fast-edge layout, protection response, insulation stress and thermal integration. |
| CoolGaN | Compact, high-frequency converters within the chosen device's voltage and power range. | Device architecture, drive interface, reverse conduction, package and loop inductance. |
| IGBT discretes / modules | Inverters and drives whose current, frequency and load profile fit an IGBT solution. | Turn-off loss, companion diode, desaturation settings, short-circuit conditions and module mounting. |
| Power diodes | Rectification, freewheeling and commutation paths. | Forward loss, reverse recovery or capacitive charge, surge duty and thermal coupling to the switch. |
Swipe horizontally on smaller screens, or focus the table and use the arrow keys.
Start from Infineon's MOSFET portfolio and official selection tools. Family positioning helps you search; it does not approve an alternate.
03 / Compare like with like
How should you compare two devices at the real operating point?
Use one row per parameter and separate columns for the original device, candidate, test conditions and pass/fail evidence. Leave missing evidence visibly unresolved.
How do limits, guarantees and typical curves differ?
Absolute maximum ratings are boundaries, not recommended operating conditions. Compare guaranteed limits with guaranteed limits; typical curves help estimation but do not establish production worst-case margins. Record the datasheet revision for each part.
Which datasheet conditions must match?
Check gate voltage, junction temperature, current, bus voltage, gate resistance and the diode or test circuit. Comparing one device's 25°C resistance with another's hot value, or switching energies measured under different commutation conditions, can reverse the ranking.
Why are current rating and total gate charge insufficient?
Continuous current capability depends on the specified cooling conditions. Gate threshold marks the onset of conduction at a small test current; it is not the recommended gate-on voltage. Check the Miller region, nonlinear output capacitance and reverse-current behavior, not just total Qg.
How do you estimate MOSFET conduction loss?
IRMS is the device-current RMS over the whole switching period; do not multiply by duty again. Use the relevant gate bias and hot resistance. For an IGBT, average vCE(t)iC(t) over the full period.
How do you estimate switching loss?
Use energies representative of the actual switching event. Check what recovery or capacitive loss is already included. Avoid double-counting; soft switching and changing load conditions need their own analysis.
When is the simple temperature estimate valid?
This estimate assumes the datasheet's junction-to-case heat path and a known case temperature. Tc is not ambient temperature. Use transient thermal impedance and the full cooling network for pulsed or load-cycling operation.
For current-rating, SOA and switching pitfalls, see Infineon's Designing with power MOSFETs application note.
Documented design case / Infineon application note
What does Infineon’s 300 W SMPS case show about load profile?
Historical reference design, Revision 1.1, October 20, 2015. Not a YURUNOX test or a current product-availability claim.
Infineon's wide-range SMPS application note distinguishes these two output ratings in Table 1. Its PFC loss study uses a 65 kHz switching frequency, a 380 V bus and a 70°C maximum ambient assumption.
Section 3.2 finds an approximately 75 mΩ loss optimum under its stated full-load conditions. The design instead selects a 190 mΩ device for a non-continuous profile alternating between full and low load with 50% full-load duty. It says continuous full-load operation needs lower resistance with the proposed heatsink.
The selection lesson: ask what the power label means, how long the peak lasts and which cooling assumptions support it. That 50% describes the load profile, not the transistor's PWM duty cycle.
Read the original application note: Table 1 and Section 3.2.
04 / Check the physical and electrical interfaces
Why can a matching package still fail the substitution?
Assorted power MOSFET package formatsPhoto: Mister rf / Wikimedia Commons, CC BY-SA 4.0.
Verify every terminal and heat-transfer surface
Compare the dimensioned drawings, not photographs. Confirm drain/source or collector/emitter assignment, exposed-pad potential, lead pitch, tolerances and land pattern. An electrically live tab, changed isolation arrangement or different mounting stack can invalidate an otherwise promising replacement.
Recheck the gate loop as a circuit
The same driver supply does not guarantee the same gate waveform. Driver impedance, source inductance, gate resistance and device capacitances interact. Review overshoot, unintended turn-on, switching speed and driver heating across the required operating range.
QDPAK: cooling and gate return change together
Infineon's CoolMOS QDPAK brief describes a top-side-cooled SMD package with a separate Kelvin source connection. That source-sense terminal lets the driver return avoid sharing the main power-source connection. The cooling surface also changes how the heatsink interfaces with the assembly.
Practical implication: compare the gate-return routing and thermal stack, not just the MOSFET die. This is a package-architecture example, not proof of compatibility with an existing board. See the QDPAK product brief.
Illustrative engineering situations / Not customer results
Which requests require a hold, controlled change or redesign?
The situations below are hypothetical. They show the questions a useful selection review should resolve, without implying that an untested candidate has passed.
“Can we buy a lower-resistance part?”
Starting point: a fixed 10 V driver and an existing 60 V MOSFET. The team has no captured worst-case regenerative voltage or switching overshoot.
Review: establish actual voltage stress and required margin first, then compare hot resistance, gate loading, diode behavior and the copper heat path.
Decision: hold the replacement. The original 60 V label does not demonstrate that either part is adequately rated for this 48 V system.
“Can SiC solve the thermal problem?”
Starting point: a silicon MOSFET stage is close to its thermal limit, but the PCB and controller were tuned around that device.
Review: separate conduction, switching and diode losses. Check the SiC candidate's specified drive, gate transients, commutation and EMI behavior.
Decision: treat it as a controlled-change or redesign study if the driver, protection or layout must change. A cooler simulation is not drop-in approval.
“The new IGBT module has the same rating.”
Starting point: purchasing finds a newer module generation with the same nominal voltage/current class and similar outline.
Review: compare the diode, switching energies, gate conditions, fault response, terminals and thermal cycling against the mission profile.
Decision: release only the tested module, drive settings and mounting configuration. A matching module rating does not preserve the old protection margin automatically.
05 / Turn a shortlist into evidence
What must simulation and hardware testing prove before release?
Keep the model version, topology, gate settings, parasitic assumptions and thermal boundary conditions with the result. Otherwise, a convincing efficiency number is difficult to review or reproduce.
What can Infineon’s official tools establish?
Infineon's finders help filter products and locate models or evaluation boards. IPOSIM supports power-loss and thermal studies for supported high-power devices and topologies, including steady-state, load-cycle and parameter-sweep analysis.
Use those results to rank candidates and identify sensitive assumptions. Check tool coverage for the exact device; do not assume every product or topology is represented.
What still needs the real board?
A model does not establish your assembled board's gate ringing, isolation stress, false turn-on, EMI, solder quality or full fault response. Recheck the accepted candidate at the relevant operating corners and with production-representative hardware.
High-voltage and fault testing belongs to qualified personnel using an approved laboratory safety plan and suitable measurement equipment.
| Review layer | Evidence to collect | Release question |
|---|---|---|
| Electrical / dynamic | Drain or collector stress, gate waveform, overshoot, current sharing, reverse commutation, dead time and startup/shutdown behavior. | Are limits and operating margins maintained across the required range? |
| Thermal / mission profile | Loss comparison, case or board temperature, justified junction-temperature estimate and transient/load-cycle analysis. | Does the unchanged or revised cooling path meet the defined duty? |
| SOA / protection | Linear-mode or pulsed SOA where relevant; fault detection and turn-off timing; device-specific avalanche or short-circuit conditions. | Does protection act within the device's supported conditions? |
| System / production | EMC and safety impact, control stability, mechanical fit, assembly checks and any customer-required qualification. | Is the exact production configuration ready for controlled release? |
Swipe horizontally on smaller screens. The test plan must reflect the product's actual hazards and qualification requirements.
06 / Close the approval loop
How should engineering, quality and purchasing approve the part?
Marked Infineon power MOSFET installed on a power-supply board© Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons).
What must engineering release?
Record the full ordering code, approved BOM and PCB revision, any gate-resistor or firmware changes, temperature/load limits, test evidence and sign-off. If two candidates require different drive settings, they are not interchangeable under one unrestricted BOM line.
What supply evidence should purchasing and quality require?
Agree the source/channel requirements, packaging, traceability records, incoming inspection and pre-shipment evidence. Confirm quantity and delivery terms separately. A certificate or sample shipment does not demonstrate electrical compatibility; a passing bench test does not establish the supply chain's provenance.
How should lifecycle be checked for the exact ordering code?
Review relevant product change notifications and any discontinuation notices. Check whether the exact device appears in the applicable longevity-program table and read its conditions. Infineon states that these plans can change, so a family label is not a blanket supply guarantee.
Make the next conversation specific
What should you send when requesting an Infineon alternative?
Give your sourcing partner enough context to distinguish an exact-part request from an engineering alternate search.
YURUNOX is an electronic-component sourcing partner. Bring the original ordering code, approved alternatives and evidence requirements to the purchasing discussion. Suitability and final release remain with your responsible engineering and quality teams.
Power-device review brief
Original manufacturer part number / full ordering code: Candidate ordering code, if any: Board, schematic and firmware revision: Application, topology and switching role: Bus range, measured transients and current profile: Gate drive, frequency, dead time and protection: Package, pinout, cooling and temperature limits: Allowed changes / fixed constraints: Qualification and acceptance criteria: Required source, packaging and traceability evidence: Quantity, delivery target and production lifetime: Engineering approval status / outstanding evidence:
Primary references
Which Infineon sources support this selection process?
- Infineon: 300 W general-purpose wide-range SMPS application note. Table 1 and Section 3.2; Revision 1.1, 2015.
- Infineon: Designing with power MOSFETs. Rating conditions, SOA and switching considerations.
- Infineon: CoolMOS QDPAK package brief. Top-side cooling and Kelvin source architecture.
- Infineon: Finder and selection tools. Official product, model and design-resource starting points.
- Infineon: IPOSIM. Supported loss, thermal and load-cycle analysis.
- Infineon: Product change notification and product longevity program. Change management and availability conditions.
This is a selection and sourcing guide, not approval of a specific replacement. Use current documentation for the exact ordering code. Infineon product and family names belong to their respective owner. The public design case and attributed photographs do not imply endorsement by Infineon or the photographers. For production, self-host optimized WebP copies of licensed images in the WordPress media library and retain the adjacent attribution.