Bourns has introduced the ACXX57SQ Series, a surface-mount air coil inductor line aimed at high-frequency television and radio receivers, radio transmitters, RF amplifiers, and tuning circuits.
The series targets designers needing high-Q inductance in a compact, pick-and-place-compatible package.
Key features and benefits
- Flat top and flat bottom construction for mechanical stability during automated pick-and-place assembly
- Typical Q value of 140 at a 50 MHz test frequency
- Tight inductance tolerance options of ±2% and ±5%
- Surface-mount termination for standard SMT lines
- RoHS compliant per Directive 2015/863 (Mar 31, 2015) and its annex
Technical highlights
The ACXX57SQ series spans an inductance range of 90 nH to 300 nH, with maximum DC resistance (DCR) ranging from 5.5 mΩ to 13.8 mΩ across the range. Minimum self-resonant frequency (SRF) runs from 0.72 GHz to 1.15 GHz, which matters directly for RF inductors used near their operating band — SRF sets the practical upper frequency limit before the component behaves capacitively rather than inductively.
Rated current is listed at 3.7 A to 5.7 A in the press release, while the Bourns RF inductors product page lists the current range for this series as 3.7 A to 5 A. This discrepancy could not be resolved because the series datasheet did not load during this review, so the current rating — and whether it is limited by DCR-driven temperature rise or by inductance roll-off — should be confirmed directly against the current datasheet before use. Operating temperature is specified from −25 °C to +125 °C. Package size, per the product page, spans 5.21 mm to 11.94 mm in length, 5.46 mm to 5.72 mm in width, and 5.69 mm in height across the inductance range.
| Parameter | Value | Notes |
|---|---|---|
| Inductance range | 90 – 300 nH | ±2%, ±5% tolerance |
| Q typ. | 140 | at 50 MHz |
| Min. SRF | 0.72 – 1.15 GHz | |
| Max. DCR | 5.5 – 13.8 mΩ | |
| Rated current | 3.7 – 5.7 A (press release) / 3.7 – 5 A (product page) | figures differ between sources |
| Operating temperature | −25 °C to +125 °C |
Typical applications
- High-frequency television and radio receivers — supported by the SRF range extending above 1 GHz
- Radio transmitters — supported by the high typical Q value and tight tolerance options
- RF amplifiers — supported by the low DCR figures at these inductance values
- Tuning applications — supported by the ±2% tolerance option, which limits circuit-to-circuit frequency drift
Application fit
The combination of sub-300 nH inductance, GHz-class SRF, and Q of 140 places this series in narrowband RF matching and tuning networks rather than power-conversion filtering, where higher inductance and current-handling parts are normally used. The ±2% tolerance option is the more relevant choice for tuned circuits where frequency accuracy compounds with other component tolerances; the ±5% option suits looser matching or amplifier bias networks.
Design-in notes for engineers
- Confirm the rated current figure against the current datasheet before locking a design, given the discrepancy between the press release and the product page
- Check DCR against the specific part number selected, since it varies by roughly 2.5:1 across the inductance range
- Verify SRF margin relative to the actual operating frequency, not just the nominal band, since board parasitics shift effective self-resonance
- Confirm land pattern and outline dimensions from the datasheet or outline drawing before layout, as only nominal package size was available from the product page at review time
Source
This article is based on the Bourns press release IC26127 (September 17, 2026) announcing the ACXX57SQ series, together with the Bourns RF inductors product page. The series datasheet could not be retrieved during this review; engineers should consult the current Bourns ACXX57SQ datasheet and documentation for final specification confirmation and design release.
References
- Bourns, “Bourns Releases New ACXX57SQ Series Air Coil Inductors” (Press Release IC26127), September 17, 2026 — https://www.bourns.com/docs/technical-documents/featured-product-bulletins/bourns_ic26127_acxx57sq_npr.pdf
- Bourns, “RF Inductors” product page — https://bourns.com/products/magnetic-products/rf-inductors
