Littelfuse Unveils Compact 3 kA TVS Diode for DC-Powered and PoE Systems

A persistent challenge in circuit protection is designing power-dense and miniaturized electronic systems. High-power systems, particularly those with DC power buses and Power over Ethernet (PoE) functionality, require robust surge protection that can handle significant transient currents without consuming excessive board space. To address this need, Littelfuse has introduced its DFNAK3 series of 3 kA transient voltage suppression (TVS) diodes that combine a high-surge rating with a compact surface-mount form factor.

The DFNAK3 series packs 3 kA of surge protection into a small package, saving PCB space compared to standard TVS options. Image used courtesy of Littelfuse

DFNAK3 Series TVS Diodes

Littelfuse has designed the DFNAK3 series to provide overvoltage protection by diverting high-current transients away from sensitive downstream components. A key performance metric for these devices is the peak pulse current rating, and the DFNAK3 series is rated at 3 kA on an 8/20 µs pulse waveform, a standard test for lightning-induced surges. This level of protection is often associated with larger, axial-leaded components or other bulkier surface-mount packages, which can be a significant constraint in space-limited designs.

A primary technical innovation of the DFNAK3 is its physical packaging. The diode is offered in a dual flat no-lead (DFN) package, which is considerably smaller than typical alternatives. According to Littelfuse, this new package has a 70% smaller footprint and is 70% lower in height than standard overcoated components. This enables engineers to implement high-power surge protection in high-density PCB layouts without compromising performance. 

Chart showing the electrical characteristics of the five models that make up the DFNAK3 series. Image used courtesy of Littelfuse

High-Surge Current Protection

The DFNAK3 series’ performance is characterized by its clamping voltage and breakdown voltage. The clamping voltage is the voltage across the diode while it is conducting the transient current, and a lower value indicates better protection for the circuits it is safeguarding. The DFNAK3 series is engineered to offer a low clamping voltage, helping to ensure that voltage spikes are suppressed effectively and to protect sensitive integrated circuits and microcontrollers.

The diodes are also designed with a breakdown voltage that is above the reverse standoff voltage, which is a necessary characteristic for reliable protection in DC power and PoE applications. Additionally, the internal construction of the DFNAK3 utilizes a glass-passivated chip junction and is lead-free and halogen-free for reliability and compliance with environmental standards. The DFNAK3 series is also engineered to meet the stringent requirements of IEC 61000-4-5 Level 4, a standard for surge immunity that is critical for equipment operating in harsh electrical environments.

The DFNAK3 series features a compact, high-power design suitable for PoE systems, DC bus protection, and DC power supplies. Image used courtesy of Adobe Stock

Surface Mount Surge Protection

The technical characteristics of the Littelfuse DFNAK3 series make it suitable for a variety of demanding applications where both robust surge protection and compact size are crucial. The diodes can be used for DC bus protection in systems such as small cells, remote radio units, and baseband units. The series’ high-surge rating and low clamping voltage are also well-suited for safeguarding DC power supplies in AI infrastructure, data centers, and other ICT equipment. The diodes are also a practical choice for PoE systems and industrial DC power supplies that operate in environments prone to voltage transients.