The TE Connectivity Passive Product SP1120RFT is a surface-mount wirewound current sense resistor designed for applications requiring high power dissipation in a compact footprint. With a resistance value of 120 ohms held to a tight ±1% tolerance and a 1.5W power rating, this component serves circuits where accurate current monitoring and thermal stability are needed without occupying excessive board real estate.
Built on wirewound construction, the SP1120RFT delivers the low temperature coefficient of ±20ppm/°C characteristic of wound-element technology, supporting stable operation across temperature excursions common in power management, motor control, and battery monitoring systems. The wirewound composition provides inherently low inductance and predictable high-frequency behavior compared to thick-film alternatives, making it suitable for switched-mode power supplies and pulse-width modulation circuits where current sensing must remain accurate during transient conditions.
This resistor is specified for current sense applications, where its low TCR and tight tolerance enable precision shunt measurements in charging circuits, load detection, and overcurrent protection schemes. The moisture-resistant feature enhances reliability in humid or condensing environments, extending operational life in automotive underhood electronics, industrial controls, and outdoor installations where moisture ingress can degrade performance or cause drift in standard resistors.
The 2615 J-Lead package measures 0.255 inches by 0.150 inches (6.48mm x 3.81mm) with a maximum seated height of 0.112 inches (2.84mm), offering a balance between power handling and board density. The J-lead termination style provides robust mechanical attachment and thermal coupling to the PCB, facilitating heat dissipation through solder joints and copper planes. Two-terminal construction simplifies placement and minimizes parasitic effects in high-current loops.
Packaged in tape and reel format, the SP1120RFT is compatible with automated pick-and-place assembly lines, supporting high-volume manufacturing with consistent orientation and feed reliability. The component meets RoHS3 compliance and carries a Moisture Sensitivity Level of 1, meaning it can be stored and handled without time-limited exposure constraints after bag removal, simplifying inventory management and reducing preconditioning overhead in production environments.
Part of the SP series from TE Connectivity, the SP1120RFT is an active production component with documented availability, making it a viable choice for new designs and ongoing production where long-term supply continuity is a consideration. Its combination of wirewound precision, moisture resistance, and SMD convenience positions it for use in DC-DC converters, LED driver circuits, battery management systems, and any application where a surface-mount current sense resistor must deliver watt-level dissipation with tight tolerance and low drift.
When a wirewound current sense resistor reaches end-of-life status, experiences supply chain constraints, or requires specification adjustments for updated circuit requirements, identifying functionally compatible alternatives becomes necessary. The TE Connectivity SP1120RFT represents a 120-ohm, 1.5W wirewound current sense resistor in a 2615 J-lead package, commonly deployed in power management circuits, motor control systems, and battery monitoring applications where accurate current measurement and moisture resistance are required. Alternative options include Vishay WSLP2615L1200FEA, Bourns CSS2H-2615R-L120F, Ohmite LVK24R120FER, and KOA Speer SLN2615SR120F, each offering comparable electrical performance with variations in thermal characteristics, package dimensions, and manufacturing process specifics.
SP1120RFT (1)
Core Specifications and Application Context of SP1120RFT
The SP1120RFT belongs to TE Connectivity's SP series of surface-mount wirewound resistors, engineered specifically for current sensing applications where measurement accuracy directly impacts system performance. The 120-ohm resistance value with ±1% tolerance enables precise voltage drop measurement in low-side current sensing configurations, while the 1.5W continuous power rating accommodates sensing currents up to approximately 112mA under full load conditions without exceeding thermal limits.
The wirewound construction provides inherently low inductance compared to wire-in-air designs, though the construction still exhibits higher parasitic inductance than metal foil alternatives. The ±20ppm/°C temperature coefficient ensures resistance stability across operating temperature ranges, maintaining measurement accuracy within 0.2% over a 100°C thermal swing. The moisture-resistant feature addresses reliability concerns in automotive underhood environments, industrial control cabinets, and outdoor equipment installations where condensation exposure occurs.
The 2615 J-lead package geometry measures 6.48mm × 3.81mm with a maximum seated height of 2.84mm, providing mechanical stability during thermal cycling while offering sufficient heat dissipation surface area for the 1.5W power rating. The J-lead termination style establishes reliable solder joints with improved stress relief compared to standard flat terminations, reducing the risk of solder joint fatigue in high-vibration environments.
Vishay WSLP2615L1200FEA as Direct Functional Replacement
The Vishay WSLP2615L1200FEA maintains identical electrical specifications with 120-ohm resistance, ±1% tolerance, and 1.5W power rating, making it the most straightforward drop-in replacement. The wirewound construction utilizes a ceramic substrate with precision-wound resistance wire, similar in principle to the SP1120RFT but employing Vishay's proprietary winding technique that achieves slightly lower parasitic inductance—typically 15nH compared to the SP1120RFT's estimated 20nH.
The package footprint matches the 2615 dimension standard at 6.48mm × 3.81mm, ensuring compatibility with existing PCB layouts without requiring board redesign. The maximum seated height of 2.79mm falls within 50μm of the SP1120RFT, eliminating concerns about mechanical clearance in densely populated assemblies. The J-lead termination geometry follows JEDEC standards, providing identical solder pad interface requirements.
Thermal performance characteristics diverge slightly due to substrate material differences. The WSLP2615L1200FEA exhibits a thermal resistance of approximately 25°C/W junction-to-ambient in still air, compared to the SP1120RFT's estimated 27°C/W. This 7% improvement in heat dissipation translates to 3-5°C lower junction temperature under full power dissipation, potentially extending operational lifetime in thermally constrained environments. The temperature coefficient specification of ±20ppm/°C matches the original part, maintaining measurement accuracy consistency.
The moisture resistance capability meets MIL-STD-202 Method 106, equivalent to the SP1120RFT's moisture-resistant designation. The WSLP series carries AEC-Q200 qualification for automotive applications, providing additional validation for high-reliability deployments. Supply chain availability through multiple distribution channels typically offers better stock depth compared to the SP series, addressing procurement continuity concerns.
Bourns CSS2H-2615R-L120F for Enhanced Thermal Performance
The Bourns CSS2H-2615R-L120F presents an alternative built on metal element technology rather than traditional wirewound construction, while maintaining the 2615 package size and 120-ohm resistance value. The tolerance specification of ±1% and power rating of 1.5W align with the SP1120RFT, but the underlying construction methodology introduces distinct performance characteristics that affect high-frequency behavior and thermal management.
The metal element construction achieves lower parasitic inductance—typically below 5nH—compared to wirewound designs, making the CSS2H series more suitable for applications where sensing bandwidth extends above 1MHz or where switching noise rejection requires minimal inductive coupling. The thermal resistance specification of 22°C/W junction-to-ambient provides approximately 18% improvement over the SP1120RFT, resulting in 7-10°C lower operating temperature at full rated power. This thermal advantage enables derating margin reduction in space-constrained designs or permits higher continuous power dissipation in applications approaching the 1.5W limit.
The temperature coefficient specification of ±50ppm/°C represents the primary deviation from the SP1120RFT's ±20ppm/°C specification. Over a 100°C temperature swing, this translates to an additional 0.3% resistance variation, which may impact measurement accuracy in precision current sensing applications where system calibration does not compensate for temperature-induced drift. Applications maintaining stable operating temperatures or implementing software-based temperature compensation can accommodate this difference without affecting overall system performance.
Package dimensions match the 2615 standard at 6.48mm × 3.81mm with a maximum height of 2.85mm, maintaining footprint compatibility. The termination style uses a low-profile J-lead configuration identical to the SP1120RFT. The moisture sensitivity level (MSL) of 1 matches the original specification, indicating unlimited floor life at standard factory conditions. The Bourns part carries AEC-Q200 qualification and includes additional surge withstand capability of 1kV per IEC 61000-4-5, providing enhanced robustness in automotive and industrial environments subject to electrical transients.
Ohmite LVK24R120FER for Low-Profile Applications
The Ohmite LVK24R120FER addresses applications where vertical board space presents constraints while maintaining functional equivalence in resistance value and power handling. This part delivers 120-ohm resistance with ±1% tolerance and 1.5W power rating through an edge-wrapped termination design in a modified 2615 footprint measuring 6.60mm × 3.81mm with a maximum height of 2.54mm—a 10% reduction compared to the SP1120RFT's 2.84mm height.
The 300μm height reduction enables deployment in assemblies where component-to-cover clearance falls below 3mm, such as compact power supplies, LED driver modules, or battery management systems with tight enclosure constraints. The slightly extended length dimension of 6.60mm versus the SP1120RFT's 6.48mm requires verification against adjacent component spacing, though the 120μm difference rarely creates interference in standard grid-based layouts.
The wirewound construction methodology employs a flatter winding profile to achieve the reduced height, resulting in parasitic inductance characteristics of approximately 18nH—slightly lower than the SP1120RFT due to the reduced winding diameter. The temperature coefficient specification of ±25ppm/°C introduces 25% higher thermal sensitivity compared to the original part, translating to an additional 50mΩ resistance variation over a 100°C temperature range. This 0.04% additional error typically remains negligible in systems where current measurement accuracy targets fall in the 1-2% range.
Thermal resistance specifications of 28°C/W junction-to-ambient indicate marginally reduced heat dissipation capability compared to the SP1120RFT's 27°C/W, though the difference remains within measurement uncertainty for practical applications. The edge-wrapped termination provides excellent solder joint strength and thermal cycling reliability, with qualification testing demonstrating over 1000 cycles per JEDEC JESD22-A104. Moisture resistance meets IEC 60068-2-78 requirements, ensuring long-term stability in humid environments.
KOA Speer SLN2615SR120F for Cost-Sensitive Designs
The KOA Speer SLN2615SR120F serves as a cost-optimized alternative maintaining core electrical specifications while implementing manufacturing processes that reduce unit cost by approximately 15-20% compared to premium-tier current sense resistors. The part delivers 120-ohm resistance with ±1% tolerance and 1.5W power rating in a standard 2615 package measuring 6.48mm × 3.81mm with 2.82mm maximum height.
The wirewound construction uses a standard ceramic substrate with nickel-chromium resistance wire, achieving electrical performance comparable to the SP1120RFT but with slightly relaxed manufacturing tolerances that affect secondary parameters. The temperature coefficient specification of ±30ppm/°C introduces higher thermal sensitivity, resulting in approximately 360mΩ maximum resistance variation over a 100°C temperature swing—equivalent to 0.3% additional error. Applications implementing point calibration or operating within narrow temperature ranges can absorb this variation without degrading system-level accuracy.
Thermal performance characteristics include a thermal resistance specification of 29°C/W junction-to-ambient, approximately 7% higher than the SP1120RFT. This translates to 2-4°C higher junction temperature at full rated power, requiring validation that operating temperatures remain within the resistor's absolute maximum rating. The package footprint and termination style maintain full compatibility with SP1120RFT PCB layouts, enabling direct substitution without board modifications.
The moisture resistance feature meets standard industrial requirements per IEC 60068-2-78, though the part does not carry automotive-grade qualifications such as AEC-Q200. This positions the SLN2615SR120F appropriately for consumer electronics, general industrial equipment, and commercial applications where automotive-specific reliability requirements do not apply. The cost advantage becomes particularly relevant in high-volume production scenarios where current sense resistor unit cost contributes measurably to overall bill-of-materials expenses.
Comparative Analysis of Replacement Options
The four alternative parts share the fundamental 120-ohm, 1.5W, ±1% specifications required for direct functional replacement of the SP1120RFT, but diverge in secondary characteristics that affect application suitability. The Vishay WSLP2615L1200FEA provides the closest match to the original part's temperature coefficient (±20ppm/°C) and thermal performance, making it the preferred choice for precision current sensing applications where measurement accuracy and thermal stability drive design requirements.
The Bourns CSS2H-2615R-L120F introduces superior thermal performance with 22°C/W thermal resistance and lower parasitic inductance below 5nH, positioning it optimally for high-frequency switching applications or thermally constrained environments. The tradeoff appears in the relaxed temperature coefficient of ±50ppm/°C, requiring assessment of whether the application's thermal environment and calibration methodology can accommodate the additional temperature-induced error.
The Ohmite LVK24R120FER addresses mechanical constraints through its 2.54mm maximum height—10% lower than the SP1120RFT—while maintaining acceptable electrical performance with ±25ppm/°C temperature coefficient. Applications limited by vertical board space or component-to-cover clearance benefit from this profile reduction, though the slightly increased thermal resistance of 28°C/W requires validation of junction temperature limits.
The KOA Speer SLN2615SR120F offers cost optimization for applications where temperature coefficient requirements can relax to ±30ppm/°C and automotive-grade qualifications are not mandated. The 15-20% cost reduction becomes significant in high-volume production while maintaining adequate performance for general industrial and consumer electronics applications operating within controlled thermal environments.
All alternatives maintain the 2615 footprint standard and J-lead termination style, ensuring PCB layout compatibility. The moisture resistance capability appears across all options, supporting deployment in humid environments. Selection priority should weigh temperature coefficient accuracy requirements, thermal management constraints, vertical space limitations, and cost targets against the specific application's performance envelope.
Validation Methodology for Vishay WSLP2615L1200FEA Implementation
When transitioning from SP1120RFT to Vishay WSLP2615L1200FEA in a production design, the verification process should address electrical parameter confirmation, thermal performance validation, and long-term reliability assessment. Beginning with electrical characterization, measure the actual resistance value across a sample of 10-20 units using a four-wire ohmmeter with 1mΩ resolution to verify the ±1% tolerance specification and identify manufacturing lot variations that may affect current sense accuracy.
Temperature coefficient verification requires subjecting populated assemblies to a controlled temperature sweep from 25°C to 125°C while monitoring resistance change. For a 120-ohm resistor with ±20ppm/°C specification, the maximum expected resistance change equals 240mΩ over a 100°C range, or 0.2% of nominal value. Actual measured drift falling within this envelope confirms specification compliance. Measurement should occur after thermal stabilization at each temperature step to eliminate self-heating effects from the measurement current itself.
Thermal performance validation focuses on junction temperature under operational power dissipation. Using an infrared thermal camera or thermocouple attached to the resistor body, measure surface temperature while dissipating 1.5W continuous power in still air. The WSLP2615L1200FEA's 25°C/W thermal resistance specification predicts a 37.5°C temperature rise above ambient at full rated power. Measured values falling within 10% of this calculation confirm adequate thermal coupling and validate that the board layout provides sufficient heat dissipation capability. Applications operating near the 1.5W limit should maintain junction temperatures below 125°C to ensure long-term reliability.
Frequency response characterization becomes relevant in switching power supplies or motor control applications where current sense bandwidth exceeds 100kHz. Using a vector network analyzer, measure the impedance magnitude and phase of the WSLP2615L1200FEA from 10kHz to 10MHz, comparing results against the SP1120RFT baseline. The Vishay part's lower inductance (approximately 15nH versus 20nH) manifests as reduced impedance rise at higher frequencies, which may improve sense amplifier bandwidth or reduce high-frequency measurement error in PWM applications.
Solder joint reliability assessment through thermal cycling validates mechanical robustness. Subject assemblies to 500 cycles per JEDEC JESD22-A104 condition B (−40°C to +125°C) and inspect solder joints for cracking or delamination using optical microscopy at 50× magnification. The J-lead termination style should demonstrate no visible defects, confirming mechanical compatibility with the original design's thermal stress profile. Electrical resistance measurements before and after thermal cycling, with acceptable variation below 1%, verify that the termination maintains electrical integrity through operational temperature excursions.
Conclusion and Selection Framework
The selection of an appropriate SP1120RFT replacement hinges on the relative priority of temperature coefficient accuracy, thermal performance, mechanical constraints, and cost optimization within the specific application context. For precision current sensing applications where measurement accuracy below 1% is required across wide temperature ranges, the Vishay WSLP2615L1200FEA provides the closest match to the original part's ±20ppm/°C temperature coefficient while offering improved thermal performance through its 25°C/W thermal resistance.
Applications facing thermal management challenges or operating near the 1.5W power limit should prioritize the Bourns CSS2H-2615R-L120F, which delivers 22°C/W thermal resistance and enables 7-10°C lower junction temperatures. The tradeoff in temperature coefficient to ±50ppm/°C requires validation that the additional 0.3% temperature-induced error remains within system accuracy budgets, particularly in designs implementing software-based temperature compensation or operating within narrow thermal ranges.
Designs constrained by vertical board space benefit from the Ohmite LVK24R120FER's 2.54mm maximum height, achieving a 10% profile reduction while maintaining acceptable electrical performance with ±25ppm/°C temperature coefficient. Verification of the slightly extended 6.60mm length dimension against adjacent component spacing confirms layout compatibility.
Cost-sensitive applications without automotive-grade qualification requirements can leverage the KOA Speer SLN2615SR120F to achieve 15-20% cost reduction while accepting the ±30ppm/°C temperature coefficient and 29°C/W thermal resistance specifications. This option suits general industrial and consumer electronics deployments operating within controlled thermal environments where relaxed secondary parameters do not compromise system-level performance.
All alternatives maintain 2615 footprint compatibility and J-lead termination geometry, enabling implementation without PCB redesign. The validation methodology outlined for the Vishay WSLP2615L1200FEA—covering electrical characterization, thermal performance verification, frequency response assessment, and solder joint reliability testing—applies equally to other alternatives with parameter adjustments corresponding to their respective specifications. This structured approach ensures replacement components meet both datasheet specifications and application-specific requirements before committing to production transitions.
