Littelfuse Brings 30 kW SMT TVS Diodes for Avionics and eVTOL

High-power transient voltage suppression has long meant bulky axial components and manual board assembly. Littelfuse is changing that with two surface-mount TVS diode series: the SM15KPA-HR/HRA and SM30KPA-HR/HRA that deliver up to 30 kW of peak pulse dissipation in a compact SPD4-1 package while meeting the lightning surge demands of DO-160 Waveform 5A Level 5.

The bidirectional TVS (top) provides symmetrical clamping for AC or differential signals, while unidirectional devices (bottom) offer polarity-specific protection suitable for DC applications. Image used courtesy of Littelfuse

DO-160 Level 5: What the Spec Actually Demands

Lightning-induced transients are among the most severe electrical threats in airborne systems. RTCA DO-160 defines the environmental test conditions for airborne equipment, and its Section 22 covers lightning-induced transient susceptibility.

Level 5 is the most stringent tier, specifying peak pulse currents that can reach hundreds of amperes depending on the waveform. TVS diodes deployed on I/O lines, power buses, and communication interfaces in aircraft must clamp these events fast enough to protect downstream ICs without failing themselves.

Circuit Diagram showing how a TVS diverts transient current to the ground. Image used courtesy of RS Components

Both new series address this with a sub-picosecond response time and rated peak pulse dissipation on the 10/1000 μs waveform. These diodes also offer low incremental surge resistance and superior clamping capability. The 30 kW rating of the SM30KPA family gives design engineers headroom even in high-exposure installations where induced current can be substantial.

Four Variants, Two Key Differences

The series comes in two power tiers and two screening levels. The SM15KPA series handles 15 kW peak pulse power with a reverse standoff voltage range of 20 V to 400 V. The SM30KPA doubles the power rating and starts at a 28 V standoff floor. Both offer unidirectional and bidirectional polarity options to cover DC power rails and AC signal lines alike.

Unidirectional and bidirectional curves. Image used courtesy of Littelfuse

Each power level comes in two variants: HR and HRA.

Both variants undergo 100% surge testing, high-temperature storage, temperature cycling, X-ray inspection, and high-temperature reverse-bias (HTRB) testing, followed by full electrical characterization, as per MIL-STD-750.

The HR version adds Group B testing, an enhanced set of mechanical and environmental checks that provide additional qualification margin for the most demanding aerospace and defense programs.

The series also carries a 30 kV ESD rating per IEC 61000-4-2, which covers data line protection against electrostatic discharge, relevant for communication and sensor interfaces exposed during ground handling or maintenance.

Traditional high-power TVS devices for avionics typically come in axial leaded packages. These require through-hole mounting, which complicates automated assembly and adds weight, both of which matter in aerospace design. The SPD4-1 surface-mount package supports standard pick-and-place assembly, letting engineers slot the devices into modern SMT production lines without a separate manual step.

The package also handles high-temperature reflow at 245°C for up to 10 seconds, compatible with lead-free solder processes. Operating junction temperature spans -55°C to 150°C, and the devices carry matte-tin, RoHS-compliant construction with whisker testing per JEDEC JESD201A.

Additional information is available on the SM15KPA-HR/HRA and SM30KPA-HR/HRA TVS Diode Series product pages.

Looking Forward

As eVTOL certification programs advance through regulatory review and next-generation avionics push for denser, lighter assemblies, the pressure on protection components to do more in less space will only grow. DO-160 Level 5 compliance is already a hard requirement in many airborne designs, and that bar is unlikely to drop. What's changing is the expectation for form factor. Axial components are increasingly out of step with modern SMT production lines.

Devices that close that gap without compromising surge handling or screening rigor will become the default choice as the aerospace supply chain modernizes. Littelfuse's move into high-power SMT TVS territory positions it early in that transition.