Bourns Introduces New High Current, Shielded Power Inductors
The miniature AEC-Q200 compliant components feature high rated current, low magnetic field radiation, and a wide operating temperature range.
Released last Monday, Bourns’ fresh inductors exploit the company’s newly-developed molding process with metal alloy powder cores. Additionally, flat wire construction serves to reduce the units’ DC resistance (DCR) as compared to other similar-sized devices.
The offerings are divided into five separate series, each with seven or eight members whose inductances range from 0.24 to 4.7 uH. The space-saving devices all feature low profiles of either 0.8 or 1.0 mm in height, with board space requirements of 2 x 1.6 mm, 2.5 x 2 mm, or 3.2 x 2.5 mm.
Bourns' new inductors. Image [modified] used courtesy of Bourns
Below, as we’ve done with several of our latest pieces covering new industry products, we’ll take a look at the engineering concepts underlying these new inductors, rather than provide a full specification overview. Those interested in such specifications are referred to the series’ separate datasheets: SRP2010TMA, SRP2012TMA, SRP2510TMA, SRP2512TMA and SRP3212A.
Magnetic Field Radiation
The AC voltage imposed on an inductor causes it to behave like an antenna, generating electric and magnetic fields that are a potent source of electromagnetic interference (EMI), which can be devastating to the operation of adjacent circuitry.
Shielding, such as that provided by Bourns’ new inductors, can reduce or eliminate this hazard. Typically, shielding brings with it the drawback of added size and weight, so the designer must carefully consider just how much is required in each unique application, taking into account costs and benefits.
In dealing with EMI, engineers can optionally utilize EMI filters to block the passage of these deleterious emissions. In their basic form, EMI filters are inductor/capacitor (LC) filters, whose resonant frequencies coincide with the parasitic signals they are designed to block.
Members of Bourns’ new inductor series not only produce less EMI, but they also offer inductance values that correspond to those required by EMI filters in many application ranges.
Flat Wire Construction for Low DCR
DCR stands for DC resistance, and for inductors, the lower the better—the “perfect” inductor has no DCR at all.
Cross section of a flat wire (left) vs. that of a round wire. Image [modified] used courtesy of Mouser/Bourns
In the illustration above, both wires feature the same cross sectional area, and will thus offer the same DCR. But the flat wire offers far more surface area.
Due to the skin effect, traveling electrons tend to move more through the surface than through the whole cross section. As such, inductors fashioned with flat wire conductors, such as Bourns’ new devices, present a higher inductance for the same DCR.
The inductance specified in an inductor’s datasheet is the inductive value measured at zero current.
However, the current passing through an inductor will rise during operation of a typical power circuit. Saturation current is the DC current at which that inductance drops to a certain percentage below the initial value.
Members of Bourns’ new series of inductors feature saturation currents ranging from 2.65 to 9.1 A.
Bourns’ new offerings are compliant with AEC-Q200. AEC stands for the Automotive Electronics Council, which was established in the 1990s by Chrysler, Ford, and GM for the purpose of “establishing common part-qualification and quality-system standards,” per the council’s site.
The body now includes a number of domestic and international players, and its standards are both extensive and of vital importance to any original equipment manufacturer (OEM) designing for the automotive environment.
AEC-Q200 specifically covers passive components, a broad category whose members range from inductors and resistors to capacitors, thermistors, varistors, resonators, crystals, and transformers. The standard comprises numerous tests, including those for flame retardance and voltage surges.
These devices will find general use in EMI filtering, and are also applicable to wearables, hard disk drives (HDD), solid state drives (SSD), smartphones, and LCD displays.
The fresh inductors are RoHS-compliant and halogen-free.
Four of the five new series operate over a temperature range of -55 to +105 °C, with the SRP3212A series specified at -40 to 150 °C.