SRP1245A-R33M Test Report: Measured Specs & Metrics

27 January 2026 64

This report provides a comprehensive analysis of the measured inductance (~330 nH), DC resistance (~9 mΩ), and saturation characteristics. These metrics are critical for determining ripple, conduction loss, and thermal margins in high-current power designs.

Background & Datasheet Snapshot

This high-current 330 nH SMD power inductor is engineered for synchronous buck regulators and point-of-load converters. Key parameters include inductance, rated DC current, and DCR, which define its performance under load.

Specs Nominal Specifications Summary

Specification	Nominal Value	Practical Design Meaning
Inductance	330 nH	Determines ripple at switching frequency
Rated DC Current	~42 A	Maximum continuous before excessive saturation
DCR (Typical)	~9 mΩ	Primary contributor to I²R loss
SRF	~90 MHz	Sets upper harmonic margin

Test Setup & Methodology

Utilized precision LCR meters and vector impedance analyzers. Tests conducted at 25°C ambient on 2 mm FR-4 boards. Samples underwent thermal cycles to ensure repeatability across 5 units.

Calibration: Open/Short/Load verification performed for all high-frequency sweeps.

Electrical Performance

Inductance Stability vs DC Bias (Measured at 500 kHz):

0A: 330nH (100%)

30A: ~247nH (75%)

High-Frequency Behavior & Parasitics

Self-Resonant Frequency (SRF)

Measured SRF at ~90 MHz ensures stability well above standard switching frequencies. Parasitic capacitance is minimized to prevent phase shifts in feedback loops.

Efficiency Impact

In a 500 kHz buck converter test, this part showed only a 0.3–0.8% efficiency delta vs low-loss generic parts, thanks to its optimized 9 mΩ DCR.

Comparative Case Study

Bench test results in a real-world synchronous buck converter (12V to 1.0V @ 500 kHz):

Output Ripple: Significantly lower RMS scaling compared to high-DCR alternatives.
Thermal Behavior: Steady-state rise of 12–18°C at 30A load on standard PCB layout.
Design Implication: High saturation headroom allows for reliable operation during transient load steps.

Selection Checklist & Design Recommendations

Layout Priority

Minimize switching loop area; use wide copper traces and multiple thermal vias.

Current Derating

Apply 20–30% derating for continuous operation in restricted airflow environments.

EMI Mitigation

Ensure SRF is at least 5x the fundamental frequency to avoid resonant emissions.

Frequently Asked Questions

How should I use the power inductor datasheet vs measured values? +

Use the datasheet for initial selection. However, always validate with measured inductance at your specific switching frequency and DC bias, as PCB parasitics and thermal conditions can shift real-world performance.

What test metrics matter most for converter efficiency? +

DCR and core loss are the primary drivers. Measure DCR via the Kelvin method and use expected RMS currents to calculate copper loss. Loss vs frequency data helps account for high-frequency core losses.

When should I derate the inductor’s rated current? +

Derate by 20–30% if ambient temperatures exceed 50°C or if cooling is limited. Saturation behavior during transient peaks should also be considered to prevent inductor saturation during sudden load changes.