Littelfuse Adds Foldback TVS Diodes for Safer DC Line Protection

Littelfuse has introduced a new surface-mount TVS diode series designed to protect DC power lines in systems where reliability is critical. Called the 5.0SMDJ-FB, the series features a 5000 W peak pulse power rating and is built around Littelfuse’s foldback technology, an approach that helps reduce clamping voltage by up to 15% compared to traditional TVS designs.

That reduction is more than a spec sheet advantage. It directly benefits downstream components like next-gen DC/DC converters, which continue to shrink in size while becoming more vulnerable to overvoltage stress. These converters now show up everywhere, from power-over-Ethernet switches to data centre racks and industrial control cabinets, making protection performance even more important.

What's Foldback and Why Does It Matter?

In a typical surge event, most TVS diodes clamp the voltage at a fixed level. The foldback mechanism in this Littelfuse series takes a smarter approach. It allows the device to clamp high initially, absorbing the brunt of the surge, but then quickly drops the clamping voltage once the peak current has passed. The result? Less energy gets through to the load, and less stress is placed on sensitive circuitry.

Importantly, the series still maintains a breakdown voltage (V_BR) that's comfortably above the reverse standoff voltage (V_R), ensuring stability under normal operating conditions.

As Jenny Chen, Product Manager at Littelfuse, put it “The 5.0SMDJ-FB Series addresses a critical design challenge, how to safeguard increasingly sensitive DC/DC converters and other power supply components from destructive transient surges. This foldback approach gives engineers a meaningful performance boost without having to redesign boards or increase component count.”

Performance, Footprint and Compatibility

The 5.0SMDJ-FB is built in the familiar DO-214AB (SMC) package and is pin-to-pin compatible with Littelfuse’s legacy 5.0SMDJ series. This allows design engineers to swap in the new parts without changing PCB layout, a key benefit for existing designs looking for an upgrade in transient protection.

Depending on the model selected, the diodes offer reverse standoff voltages from 5 V up to 170 V, with peak pulse currents up to 73 A. They are rated for a 10/1000 µs waveform and are compliant with IEC 61000-4-2 and 61000-4-5 standards for ESD and surge protection.

Application Areas

The series is suited to a wide range of DC line protection use cases, including:

• Power over Ethernet (PoE) infrastructure
• Server and AI compute systems
• Telecom equipment
• Industrial DC distribution
• High-reliability ICT power supplies

As designs move toward higher efficiency and component density, transient events can no longer be treated as edge cases, they’re design-critical. Littelfuse’s foldback TVS diodes offer a compact, scalable way to help meet those protection goals.

The 5.0SMDJ-FB series is available now in tape and reel packaging (3,000 pcs), with samples available through Littelfuse’s authorised distribution partners.

Read the original announcement here.

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