Bourns Adds ±3% Tolerance Options to AEC-Q200 CSS4C-1216 Shunts

Bourns has expanded its CSS4C-1216 series of automotive-grade current-sense resistors with new resistance values and tolerance options, including a ±3% tolerance offering. The parts carry AEC-Q200 qualification and target high-current circuits in battery-management systems, power modules, frequency converters, and industrial electronics.

The series handles up to 5 W at 100°C — the headline figure that determines where these shunts fit. Designers of BMS master controllers, traction inverters, and industrial frequency converters now have a validated component that keeps its electrical characteristics stable under elevated temperature and continuous load.

Why the construction matters

The CSS4C-1216 relies on three design choices that directly affect measurement accuracy. First, Bourns builds the element as an electron-beam welded metal strip, which the company says delivers excellent long-term stability in current-sensing applications. Second, the series specifies inductance below 2 nH, reducing measurement error in high-current circuits where parasitic inductance distorts fast current transients. Third, a four-terminal Kelvin configuration separates the current path from the sense leads, so voltage measurement excludes lead and termination resistance.

The Kelvin connection is the physics point that changes buying decisions here. In a conventional two-terminal shunt, the millivolt sense signal sits across the same contacts that carry tens of amps, so contact resistance — which drifts with temperature and aging — becomes part of the measurement. Four terminals route the sense lines directly to the resistive element, eliminating that error term and justifying the tighter ±3% tolerance option now available.

Qualified for the automotive environment

AEC-Q200 compliance anchors the series in automotive use, where OEMs require validated reliability data before a passive component enters a production design. Bourns states the parts maintain stable electrical characteristics while operating under elevated temperatures and continuous load — the two stress conditions that dominate underhood and battery-pack sensing applications.

The datasheet claims to keep separate from measured behavior: the 5 W, sub-2 nH, and long-term stability figures are vendor specifications, published without independent test conditions in the announcement. Buyers specifying the series should request the full AEC-Q200 qualification report and the stability drift data versus temperature from Bourns or its distributors before committing the part to a safety-relevant sensing function.

Where the series fits

Target applications named by Bourns include:

• Current sensing in high-current rails
• Battery-management systems
• Power modules
• Frequency converters
• General industrial electronics

The combination of 5 W power handling, sub-2 nH inductance, and Kelvin sensing positions the parts between small-format chip shunts and larger bolt-down assemblies — the middle ground where 48 V mild-hybrid systems, server power supplies, and industrial drives operate.

The CSS4C-1216 series is available now through Bourns' authorized distribution network. Full specifications and ordering information are published on the company's website.

The open question for design teams: does a ±3% tolerance option on an AEC-Q200 metal-strip shunt cover your BMS accuracy budget, or does your application still demand the 0.5%–1% class that precision foil and thinner-film alternatives provide at lower power ratings?