Evaluating SiC MOSFET products for power converters

Written by

Quest Semi

3 Nov 20266 min read

SiC MOSFET products for power converters need to match the converter’s voltage and thermal conditions, the required package, and the intended application—not just a headline current or resistance value. We outline a practical way to screen Quest Semi’s catalog, identify mismatches early, and check candidate details before making a design decision.

Explore Quest Semi’s SiC MOSFET range

Quest Semi’s catalog includes SiC MOSFET candidates at 650 V, 1200 V, and 1700 V, with different listed current, resistance, and package details. Start with those published attributes, then check each candidate’s datasheet against the converter’s requirements.

Our SiC MOSFET range is a starting point for comparing products. The listed products include 650 V options in TO-247 and TO-220F packages, a 1200 V TO-247-4L option, and a 1700 V TO-247 option. A package name or a headline electrical figure alone does not establish suitability: operating conditions and the full datasheet matter.

For example, QSJZ120N21, 115 A, 1200 V, 20 mΩ, TO-247-4L is our product. Its catalog name identifies a 1200 V rating, 115 A, 20 mΩ, and a TO-247-4L package. Treat these as screening details, not a complete design qualification. Confirm how the datasheet defines each rating and under what conditions it applies.

A second candidate is QSJJ170R800, 8.7 A, 1700 V, TO-247, also our product. The higher listed voltage rating does not automatically make it a substitute for a lower-voltage device: the listed current differs, and the required operating point, switching conditions, thermal path, and protection design still need review.

For a 650 V requirement, the catalog includes QSJW065R26, 99 A, 650 V, TO-247. Compare its published data with the actual converter conditions rather than assuming that a matching nominal voltage makes it a fit. The Quest Semi SiC devices catalog can help identify candidates; use the corresponding product information and datasheet to verify ratings and application fit.

Match voltage ratings to converter requirements

Choose a voltage class by comparing the device rating with the converter’s bus voltage and expected electrical stresses, then verify the operating limits and design margin in the datasheet. Nominal voltage alone is not a selection rule.

Start by documenting the maximum bus voltage across operating modes, including relevant transients and switching-node behavior. Then compare that requirement with the candidate’s rated voltage and the conditions attached to its datasheet specifications. The design must keep the device within applicable limits; the required margin depends on the converter topology, switching behavior, protection, and operating environment.

A 650 V candidate, for example, should not be selected merely because a system is commonly described as a “650 V design.” Establish the actual maximum voltage at the device terminals and the relevant transient conditions. Likewise, moving to a 1200 V or 1700 V rating is not automatically a complete solution: check current capability, losses, package, thermal conditions, and the device’s switching limits.

If a customer requests a specific combination such as 1700 V, 160 mΩ, and TO-247, verify all three requirements separately. A product that matches the requested voltage but not resistance or package is not an exact match. Do not present a nearby catalog candidate as equivalent; document the deviation and ask whether the requirement can change before shortlisting it.

Switching conditions also affect voltage stress and device losses. Gate-drive settings, parasitic inductance, layout, and protection choices are part of the evaluation, not details to postpone until after choosing a part. For broader design context, see our guide to SiC MOSFET trade-offs.

Check package and application fit

A package fits only when its footprint, terminals, insulation needs, assembly method, and thermal interface work with the converter layout and cooling arrangement. Confirm the exact package variant in the product information and datasheet before treating it as interchangeable.

A TO-247 listing and a TO-247-4L listing should not be assumed to have identical connections or layout requirements. Check the package drawing, pin arrangement, mounting dimensions, and required clearances against the PCB and mechanical design. If the existing footprint is for TO-220F, a TO-247 candidate may require a different board and thermal arrangement even when its voltage class appears appropriate.

The application determines which data deserves attention. For a converter with frequent switching, assess switching energy and test conditions alongside on-state resistance. For a design constrained by heat removal, check thermal resistance, mounting conditions, and the datasheet’s limits. Current ratings also depend on stated conditions; they do not independently tell you the current a device can carry in your assembled system.

A smaller physical package is not automatically a better fit if it conflicts with the required thermal path, isolation, assembly process, or mechanical clearances. Conversely, a familiar package should not outweigh an electrical mismatch. Compare the package drawing and assembly constraints with the real layout before advancing a candidate.

Use the SiC MOSFET datasheet checklist to organize that review. For reliability-related evaluation, IEC 63275-2:2022 specifies a test method for assessing changes in SiC MOSFET on-state voltage, on-state resistance, and reverse drain voltage due to body-diode operation. That standard describes a test method; it does not by itself establish a particular product’s performance or suitability.

Use the datasheet to shortlist SiC MOSFET products

A useful shortlist keeps only candidates whose documented voltage, electrical ratings, package, thermal conditions, and application requirements align with the converter specification. Record the evidence for each match and flag any unresolved mismatch.

Review the sic mosfet datasheet using this sequence:

1. Confirm the voltage rating and compare it with the system’s maximum operating voltage and relevant transient conditions.
2. Check on-state resistance and current ratings, including the datasheet conditions attached to those values.
3. Verify the package designation, package drawing, terminal configuration, and fit with the mechanical and PCB design.
4. Compare switching and gate-drive information with the converter’s switching frequency, control approach, and expected losses.
5. Assess thermal data against the actual mounting and cooling arrangement, not an assumed ideal condition.
6. Note protection requirements and confirm that the design can keep the device within its specified operating limits.
7. Record which requirements are met, which remain uncertain, and which are not met.

This method helps distinguish a near match from a true candidate. If a requested specification calls for 1700 V, 160 mΩ, and TO-247, a 1700 V device with a different listed resistance does not satisfy the full requirement simply because its voltage and package align. Ask the project owner whether the resistance requirement is fixed; if it is, keep searching rather than silently relaxing it.

When a catalog listing and a datasheet appear to describe a product differently, resolve the discrepancy before using the part in a design. Confirm that the document corresponds to the exact product identifier and package variant, and compare its ratings and test conditions with the project specification. A device name is a useful search key, not a replacement for this check.

The shortlist should make any compromise visible: a different voltage class, package, or resistance is a specification deviation, not an equivalent choice. Have a qualified power-electronics professional review the device and protection design for the specific converter before committing to a selection.

Recommended next steps

A short, documented comparison turns a broad catalog search into a practical decision by linking each candidate to a requirement and its supporting datasheet evidence.

1. Write down the converter’s bus range, maximum device-terminal voltage, transient conditions, and required design margin.
2. Record required resistance, current, package, cooling arrangement, and application conditions as separate pass-or-fail criteria.
3. Compare catalog candidates against those criteria and remove any part with a hard voltage or package mismatch.
4. Open the product information and datasheet for each remaining candidate, then verify rating definitions, test conditions, package drawings, switching data, and thermal limits.
5. Document unresolved differences and obtain design review before selecting a device.