PTVS Models Meet High Surge Current Protection Requirements in Smallest DFN Package

Measuring just 8mm x 6mm with a minimal height of 2.5mm, the Bourns PTVS1 and PTVS2 models allow designers the option of placing circuit protection on the back side of the PCB – a huge advantage compared to legacy PTVS solutions.

 

Image used courtesy of Bodo’s Power Systems [PDF]

 

Designed to provide enhanced protection against a wide range of ESD, lightning and induced switching transient threats, Bourns’ PTVS devices are excellent circuit protection solutions particularly well-suited for highly exposed applications such as PoE and telecom baseband units (BBUs) and remote radio units (RRUs). Rated for handling 1 kA or 2 kA 8/20μs surge current (IEC 61000-4- 5) with each current rating offered in eight voltages from 22V to 86V, designers can select the precise protection strategy for their applications. Although their small size might suggest these are crowbar technology, they’re actually bidirectional voltage clamping devices. These new PTVS products are at home on either AC or DC lines delivering power or control signals.

The applications that can benefit from highly reliable, compact surge protection also include:

• 28 VAC control lines used in residential, commercial, and industrial HVAC systems.
• PoE for kiosks, security cameras, and other remote systems.
• Nominal 48 VDC systems in server applications, remote Wi-Fi, 5G radio systems, and industrial charging systems.
• 24 VDC industrial controls where failures can lead to expensive downtime.

Many PTVS devices are known to exhibit a “fold-back” voltage characteristic where the voltage across the device drops with increasing current that can allow power to flow from the power supply to the protection component.

Bourns engineers used silicon design modeling to create a highly controlled fold-back feature that results in ultra-low peak clamping voltages that avoid follow-on currents. Peak clamping voltages are maintained above the minimum rated breakdown voltage and, at most, just a few volts above the maximum rated breakdown voltage.

Low clamping voltage means the circuit designer can minimize the voltage ratings required for downstream components and still maintain healthy design margins. This may allow for lower cost components downstream.

The optimized fold-back feature helps ensure uniform breakdown that minimizes “current crowding” during the surge event. Such current crowding reduces the active area of silicon handling the surge power. Minimizing this effect has another benefit – the smaller silicon die required translates into the small area footprint of the package.

Qualified to JEDEC standards, the key design specifications for Bourns’ industry-first DFN packaged PTVS1 and PTVS2 products are highlighted below:

 

PTVS1 - PTVS2	Rated Voltage	Breakdown Voltage		Peak Clamping Voltage
		Minimum	Maximum
PTVSx-022C-H	22	24	27	28
PTVSx-026C-H	26	28	32	30
PTVSx-029C-H	29	32	35	34
PTVSx-043C-H	43	48	53	56
PTVSx-058C-H	58	64	70	67
PTVSx-066C-H	66	72	80	86
PTVSx-076C-H	76	85	95	91
PTVSx-086C-H	86	96	105	99

 

 

This article originally appeared in Bodo’s Power Systems [PDF] magazine.