Littelfuse has announced the AK-FL Series FlatSuppressX TVS Diodes, axial-leaded transient voltage suppression diodes designed to protect high-voltage DC aviation power systems from transient overvoltage events while delivering a flat, low, and stable clamping voltage.
As aviation and eVTOL platforms adopt higher-voltage 270-800V DC power architectures, engineers face a critical design challenge: selecting transient protection that limits clamping voltage tightly enough to prevent latch-up in Solid-State Power Controller (SSPC) modules and other high-voltage semiconductor devices, without compromising surge robustness. Using Littelfuse proprietary FlatSuppressX technology, the AK-FL TVS diodes leverage an advanced foldback/snapback I-V characteristic to maintain a near-constant, low clamping voltage during fast transients and high-energy surge events – helping designers protect sensitive power electronics while meeting the demands of modern aviation power distribution.
Unlike conventional TVS devices, which can exhibit higher and less predictable clamping voltages as surge current increases, FlatSuppressX devices tightly control transient response while avoiding latch-up risk. This approach gives engineers greater flexibility to select lower voltage-rated semiconductors in high-voltage power circuits, improving design efficiency without sacrificing protection.
“The key advantage of FlatSuppressX technology is its ability to deliver a stable, low clamping voltage even under extremely high-energy surge conditions,” said Charlie Cai, Director of Product Management, Protection Business, Littelfuse. “For aviation applications, that means engineers can better protect SSPC modules and other sensitive semiconductor devices from latch-up, while meeting the reliability demands of DO-160 and MIL-STD-750 environments.”
The AK-FL Series is available in three current ratings (6, 8kA, and 10kA @ 8/20µs), offering scalable surge protection options for different aviation power system requirements. Each device is up-screened per MIL-STD-750 test methods to provide the high reliability required for avionics applications. The AK-FL Series is the first FlatSuppressX TVS diode designed for aviation and eVTOL power protection, extending the proven FlatSuppressX platform beyond automotive systems into high-voltage avionics applications.
Key features and benefits
- FlatSuppressX technology: advanced foldback I-V characteristic maintains a flat, stable, and low clamping voltage, helping avoid latch-up risk in high-voltage circuits
- High surge capability: 6, 8, and 10kA (8/20µs) surge current ratings across the series
- High-reliability screening: 100% screened per MIL-STD-750 methods, including vision inspection, surge test, temperature cycling, and HTRB
- RTCA DO-160 compliance: supports avionics environmental qualification requirements
- Design flexibility: enables use of lower voltage-rated semiconductors in high-voltage power circuits, improving cost efficiency
The devices are optimised for protecting DC power rails and other vulnerable circuits in high-voltage aviation power systems, particularly where sensitive semiconductor devices require precise clamping control. The axial-leaded package is halogen-free, RoHS-compliant, and Pb-free E4 terminated, and supports both reflow and wave soldering.
Target markets and applications
- Aerospace and defence 270 V–800 V DC aviation power trains
- Solid-State Power Controller (SSPC) circuits
- eVTOL and next-generation aircraft electrical systems
- DC power rail protection in high-reliability avionics
By combining high-reliability screening with a flat, low clamping voltage, the AK-FL TVS diodes help engineers design more robust and reliable protection for next-generation aviation power electronics.
