AK3-A Axial Leaded TVS Diodes

Introduction

Littelfuse AK3-A is a family of axial-leaded transient-voltage-suppression (TVS) diodes designed for severe surge-test environments on AC and DC lines. The series is technically notable for combining a 3 kA current rating with low clamping characteristics, sharp breakdown behavior, and low slope resistance in a glass-passivated junction construction. These characteristics position the devices as an alternative to traditional MOV-based approaches where controlled surge response is important.

What it does

AK3-A devices limit transient overvoltage events on power or line interfaces by entering breakdown at a defined voltage range and diverting surge current. The family covers reverse standoff voltages from 430 V to 860 V, with maximum breakdown voltages spanning 499 V to 998 V.

The diodes are intended for demanding AC and DC line-protection duties and provide ultra-low clamping characteristics compared with traditional MOV solutions. Their specified maximum reverse leakage current is 10 μA, measured with a 10 mA test current, while the maximum temperature coefficient is 0.1%/°C.

For larger protection requirements, devices may be connected in series and/or parallel to increase the supported surge-current capability. The series also includes stated ESD protection ratings of 15 kV for air discharge and 8 kV for contact discharge under IEC 61000-4-2.

Applications

Potential uses that follow from the stated line-surge protection role include:

• AC line transient protection circuits
• DC power-line surge protection
• Equipment intended for severe surge-test environments
• High-voltage interfaces requiring 430 V to 860 V reverse standoff options
• Protection assemblies using series or parallel TVS-device arrangements for increased surge-current handling

Design considerations

AK3-A parts use an axial-leaded package, which can suit through-hole-oriented protection layouts and allow straightforward series or parallel connections. The devices support both reflow and wave soldering, providing flexibility for manufacturing processes.

Voltage selection should account for the device’s reverse standoff and breakdown ranges in relation to the normal line voltage and the required protection threshold. Designers should also consider the 3 kA current rating, the stated low-clamping behavior, and the operating junction-temperature range of -55°C to +125°C when evaluating surge-protection arrangements. Storage temperature is specified from -55°C to +150°C.

The series is RoHS compliant and lead-free. It is also recognized under UL 497B as an isolated loop circuit protector.

Availability and further information

The source/distributor link on this page provides further product information for the Littelfuse AK3-A axial-leaded TVS diode family.