Bourns Says its New PTVS Are First Available in DFN Packages
The fresh power transient voltage suppressors (PTVS) measure only 8 x 6 x 2.5 mm while offering 1 and 2 kiloamp surge protection.
Looking to meet the growing demand for compact solutions in the handling of high-power 8/20 µs surges, Bourns yesterday introduced its new, surface-mounted PTVS1 and PTVS2 series of power transient voltage suppressors (PTVS), the first it says to be housed in DFN packages.
The result of that packaging is a footprint up to 50% smaller than those of competing devices, which are typically only offered in “bulky over-molded or through-hole packages,” said Jennifer Joseph, semiconductor product line manager at Bourns.
Bourns' PTVS1 and PTVS2 series. Image [modified] used courtesy of Bourns
In another first, the PTVS2 series is also the industry’s sole PTVS to sport surge handling capability at up to 2 kA, Bourns said, echoing a trend of ramping surge protection requirements in a wide swath of next-gen AC and DC line protection applications, the company noted.
A PTVS is a two-pole device connected across a line to protect that line against the short, powerful surges that are often the result of lightning strikes, inductive switching surges, or transient voltage surges.
Both the 1 kA PTVS1 and the 2 kA PTVS2 series feature members offering standoff voltages of 22, 26, 29, 43, 56, 66, 76, and 86 V.
But before we delve further into series specifics, let’s look at a few key specifications that are vital to an understanding of what these devices can do.
Standoff, Breakdown, and Clamping Voltage
Standoff Voltage
The standoff voltage is the maximum voltage that a transient voltage suppressor can be relied on to not disturb. For example, for protecting a device that receives a 5 V data signal, the suppressor’s standoff voltage must be greater than 5 V.
Breakdown Voltage
Breakdown voltage and clamping voltage are all too easily confused.
The breakdown voltage is always higher than the standoff voltage; it is the voltage across the PTVS that the device begins to notice as a serious threat, prompting it to turn on. Below this point, the PTVS will not affect the voltage across the diode, and the current across the diode is close to zero.
Clamping Voltage
Clamping voltage, somewhat higher than breakdown voltage, is the voltage level above which the PTVS literally “clamps down.” At this point, the PTVS will absorb the surge current. The PTVS will not allow the line to exceed the clamping voltage, unless the diode itself becomes incapacitated.
These specifications are fully spelled out for both the PTVS1 and the PTVS2 in their respective datasheets.
What is An 8/20 µs Surge?
An 8/20 µs surge reaches its peak current in 8 microseconds and winds down to 50% of that peak in 20 microseconds.
An 8/20 µs surge. Screenshot used courtesy of Bourns
This power profile is considered typical of a lightning strike, which is why it is widely accepted as an industry standard.
Important Considerations
These units are bidirectional. Their breakdown voltages are specified at the point at which the diodes conduct—10 mA. At a frequency of 10 kHz, members of the PTVS1 exhibit capacitances ranging from 0.5 to 2.0 nF, while capacitances for the PTVS2 units span between 1.0 and 4.0 nF.
Applications
The PTVS1 and PTVS2 series offer AC and DC line protection for exposed power over internet (PoE) ports. They are also applicable for high-power DC bus protection in use cases including 5G small cell, remote radio units (RRUs), and baseband units (BBUs) in wireless base stations.
Physical and Environmental Considerations
PTVS1 and PTVS2 units operate over a -55 to +125 ℃ temperature range, and are both RoHS-compliant and halogen-free. Series members also meet IEC 61000-4-5 8/20 μs current surge requirements.
