AK3-FB Axial Leaded TVS Diodes

Introduction

Littelfuse AK3-FB is a family of axial-leaded transient-voltage-suppression (TVS) diodes for protecting AC and DC lines in severe surge-test environments. Using glass-passivated junction technology, the series is specified for 3 kA surge-current protection and is notable for its fast response and ultra-low clamping characteristics relative to metal oxide varistors.

What it does

AK3-FB devices are intended to suppress transient overvoltage events on AC or DC power lines. The diodes provide a low-impedance path during a surge, helping limit the voltage presented to downstream circuitry.

The series supports 3 kA current protection and includes stated ESD protection levels of 15 kV air discharge and 8 kV contact discharge under IEC 61000-4-2. It also identifies IEC 61000-4-4 electrical fast transient (EFT) protection as an applicable standard.

For applications requiring greater surge-current capability, devices may be connected in series and/or parallel. The specified failure mode is a short circuit when exposed to voltage or current beyond the device’s rating.

Applications

• AC line transient suppression
• DC power-line surge protection
• Equipment intended for severe surge-test environments
• Input protection stages requiring ESD and EFT resilience
• Higher-current protection networks using series or parallel TVS arrangements

Design considerations

The AK3-FB series uses an axial-leaded package with silver terminal finish, which should be considered when planning board layout, lead forming, and assembly processes. The parts support both reflow and wave soldering, providing flexibility for compatible manufacturing flows.

Series or parallel connections can be used for higher surge-current protection solutions, but the electrical behavior and fault response of the complete arrangement should be evaluated at the system level. Designers should also account for the stated short-circuit failure mode under over-specified voltage or current conditions.

Availability and further information

The source/distributor link on this page provides further information on the Littelfuse AK3-FB axial-leaded TVS diode family. Refer to the available datasheet links on the page for detailed electrical ratings, selection guidance, and application-specific design information.