BLM18AG102SN1D provides 1,000 Ω impedance ±25% at 100 MHz, 450 mA rated current and 0.5 Ω max DC resistance — making it a common 0603 ferrite bead choice for EMI suppression in compact designs. This part matters to PCB designers because it balances high-frequency attenuation with modest series loss, useful for power-rail noise control in consumer and industrial electronics.
The following synthesizes the latest datasheet highlights, practical layout and thermal guidance, verification steps and substitution rules so engineers can decide quickly whether the Murata bead fits their design constraints.
Point: BLM18AG102SN1D is a Murata BLM-series SMD ferrite bead in an 0603 (1608 metric) package used for targeted EMI suppression. Evidence: Datasheet nominal values show 1 kΩ impedance at 100 MHz and a 450 mA rated current. Explanation: That combination makes this bead ideal for single-line power filtering near ICs, choke function on sensitive signal traces, and decoupling chains where PCB real estate is limited. Refer to the Murata datasheet for official mechanical and electrical dimensions.
Point: Within the BLM family, variants trade impedance, DC resistance and current handling. Evidence: Compared to lower-impedance 0603 beads, the 1 kΩ class raises high-frequency attenuation but increases series loss and thermal stress at high DC. Explanation: Choose this 1 kΩ@100 MHz bead when conducted noise sits in the 10–500 MHz band and available margin for series resistance is acceptable; choose lower-impedance BLMs for higher-current rails or where voltage drop must be minimized.
Point: Key absolute values determine allowable in-system use. Evidence: Impedance = 1,000 Ω ±25% @ 100 MHz; rated current = 450 mA (at upper operating conditions); DC resistance (max) = 0.5 Ω; single circuit. Explanation: These figures imply designers should derate working current for sustained thermal loading and verify insertion loss on populated boards rather than rely solely on free-air datasheet numbers.
| Parameter | Value |
|---|---|
| Impedance (100 MHz) | 1,000 Ω ±25% |
| Rated current | 450 mA |
| DC resistance (max) | 0.5 Ω |
| Package | 0603 (1608 metric) |
Point: Ferrite beads show frequency-dependent impedance rather than a simple inductive response. Evidence: The datasheet impedance-vs-frequency curve peaks in the 10s–100s of MHz, delivering resistive damping where EMI energy concentrates. Explanation: For designers this means the BLM18AG102SN1D attenuates high-frequency noise effectively; however, impedance drops outside its optimal band and it should not be used where broadband low-frequency filtering is required.
Point: Operating temperature and current interact to change bead behavior. Evidence: Typical operating ranges span low-to-high ambient conditions and rated current is specified for acceptable deformation of characteristics. Explanation: Engineers should margin the 450 mA rating by accounting for PCB copper heat-sinking, ambient temperature, and duty cycle. Use temperature-rise measurements on a populated board to validate steady-state loss and avoid long-term impedance drift.
Point: Correct land pattern and reflow profile preserve performance and assembly yield. Evidence: Murata mechanical drawings list land pads for 0603 beads and recommend standard SnAgCu reflow thermal profiles. Explanation: Use manufacturer-recommended footprint to avoid tombstoning or lift; order in reel quantities for pick-and-place; treat as passive parts with typical handling and ESD precautions. Check the datasheet for exact pad dimensions before final PCB CAM.
Point: Placement determines effectiveness. Evidence: Practical layouts put the bead either at source (to block upstream noise) or at load (to protect sensitive ICs), often paired with a decoupling capacitor to form an RC notch. Explanation: Keep traces short on both sides, minimize parallel loops, place bead close to the pin being protected, and avoid adding series inductance that could form unwanted resonances with local capacitance.
Point: Measured attenuation and S-parameter tests validate choices. Evidence: Bench tests commonly show several dB to tens of dB reduction in conducted noise within the bead’s effective band. Explanation: Measure insertion loss and S21 on the populated board; use time-domain probing to verify ripple reduction on power rails. Remember the bead also adds small series resistance that can affect low-voltage rails under heavy load.
Point: Always download the official PDF before release. Evidence: The manufacturer’s product information module and authorized distributors carry the latest revision. Explanation: Verify package code, ordering suffixes (e.g., reel or cut-tape variants), RoHS/REACH declarations and reel size. Cross-check markings and batch codes on samples against the manufacturer specification to ensure authenticity.
Point: Substitutes require matching multiple parameters. Evidence: Equivalents must be compared on impedance at 100 MHz, rated current, DCR and package. Explanation: When swapping parts search for “ferrite bead 0603 1kΩ 450mA” and perform A/B tests on a pilot run to confirm thermal and EMI performance before wide substitution.
Measure insertion loss (S21) on the populated board across the target frequency band and perform time-domain probing of the supply rail under representative loads. Compare measured impedance and temperature rise against expected datasheet behavior and adjust placement or add decoupling as needed.
Use the Murata-recommended 0603 land pattern to minimize solder-attach issues; follow standard SnAgCu reflow profiles and control ramp rates to prevent tombstoning or excessive thermal stress. Handle reels with normal passive-component precautions and verify pad solderability on the PCB stack-up.
Prioritize matching impedance at 100 MHz, rated DC current and maximum DC resistance, then verify the impedance-vs-frequency curve shape and thermal derating. Always pilot-test substitutes on a small production run to confirm EMI and power-integrity outcomes.