Z0402C121CSMST Equivalent & Substitute Parts

Part Overview

The Z0402C121CSMST is a 120 Ohm ferrite bead manufactured by KEMET in the 0402 (1005 Metric) surface mount package. This single-line signal filter component operates at 100 MHz impedance with a maximum current rating of 350mA and 450mOhm DC resistance. The part is classified as obsolete, necessitating identification of active equivalent alternatives that maintain electrical and mechanical compatibility for ongoing production and repair applications.

Key Parameters

Parameter	Value
Impedance @ Frequency	120 Ohms @ 100 MHz
Package / Case	0402 (1005 Metric)
Mounting Type	Surface Mount
Current Rating (Max)	350mA
DC Resistance (DCR) (Max)	450mOhm
Operating Temperature	-55°C ~ 125°C
Number of Lines	1
Filter Type	Signal Line
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the Z0402C121CSMST is determined by the following critical parameters:

Mandatory Matching Parameters:

Impedance @ Frequency: 120 Ohms @ 100 MHz
Package / Case: 0402 (1005 Metric)
Mounting Type: Surface Mount
Number of Lines: 1
Operating Temperature Range: -55°C ~ 125°C
RoHS3 Compliance
MSL Rating: 1 (Unlimited)

Allowable Variation Parameters:

Current Rating (Max): Substitute parts with equal or greater current capacity are acceptable
DC Resistance (DCR) (Max): Substitute parts with equal or lower DCR are acceptable
Height (Max): Substitute parts with equal or lesser height are acceptable
Filter Type: Signal Line designation is preferred but not mandatory for electrical equivalence

Substitute parts are grouped into two categories: Direct Equivalents (matching all mandatory parameters with improved or equivalent electrical performance) and Functional Alternatives (matching all mandatory parameters with different filter type classification).

Parameter Comparison

Manufacturer Part Number	Manufacturer	Impedance @ 100 MHz	Current Rating (Max)	DCR (Max)	Height (Max)	Filter Type	Product Status	Packaging
Z0402C121CSMST	KEMET	120 Ohms	350mA	450mOhm	0.022" (0.55mm)	Signal Line	Obsolete	Tape & Reel (TR)
74279271	Würth Elektronik	120 Ohms	500mA	200mOhm	0.022" (0.55mm)	Signal Line	Active	Cut Tape (CT) & Digi-Reel®
7427927112	Würth Elektronik	120 Ohms	350mA	350mOhm	0.022" (0.55mm)	Signal Line	Active	Tape & Reel (TR)
BBNQ00100505121Y00	Pulse Electronics	120 Ohms	350mA	400mOhm	0.024" (0.60mm)	Not Specified	Active	Tape & Reel (TR)
BBSJ00100505121Y00	Pulse Electronics	120 Ohms	500mA	250mOhm	0.024" (0.60mm)	Signal Line	Active	Tape & Reel (TR)
BBSY00100505121Y00	Pulse Electronics	120 Ohms	550mA	190mOhm	0.024" (0.60mm)	Not Specified	Active	Tape & Reel (TR)
GZ1005D121CTF	Shenzhen Sunlord Electronics Co., Ltd.	120 Ohms	400mA	180mOhm	0.026" (0.65mm)	Signal Line	Active	Tape & Reel (TR)
GZ1005E121CTF	Shenzhen Sunlord Electronics Co., Ltd.	120 Ohms	500mA	250mOhm	0.026" (0.65mm)	Signal Line	Active	Tape & Reel (TR)
GZ1005U121CTF	Shenzhen Sunlord Electronics Co., Ltd.	120 Ohms	500mA	200mOhm	0.026" (0.65mm)	Signal Line	Active	Tape & Reel (TR)
HPZ1005U121-R60TF	Shenzhen Sunlord Electronics Co., Ltd.	120 Ohms	600mA	250mOhm	0.026" (0.65mm)	Power Line	Active	Tape & Reel (TR)

Engineering Selection Recommendations

Tier 1 - Preferred Substitutes (Identical Footprint and Height):

The 7427927112 (Würth Elektronik) and 74279271 (Würth Elektronik) are the primary recommended substitutes. Both maintain the 0.022" (0.55mm) maximum height of the original Z0402C121CSMST, ensuring compatibility with existing PCB layouts and assembly processes. The 7427927112 matches the original current rating of 350mA while providing superior DC resistance performance (350mOhm vs. 450mOhm). The 74279271 offers enhanced current capacity (500mA) with significantly improved DCR (200mOhm), suitable for applications requiring higher current headroom. Both parts are active products with ROHS3 compliance and MSL 1 rating.

Tier 2 - Compatible Substitutes (Slightly Increased Height):

The BBSJ00100505121Y00 (Pulse Electronics), GZ1005U121CTF (Shenzhen Sunlord Electronics), and BBSY00100505121Y00 (Pulse Electronics) provide functional equivalence with maximum heights of 0.024" to 0.026" (0.60mm to 0.65mm). These parts exceed the original current rating and provide improved or comparable DC resistance. Height variation requires verification against PCB assembly constraints and clearance requirements. All three are active products with full compliance certifications.

Tier 3 - Functional Alternatives:

The GZ1005D121CTF (Shenzhen Sunlord Electronics) and HPZ1005U121-R60TF (Shenzhen Sunlord Electronics) meet all electrical and mechanical parameters. The HPZ1005U121-R60TF is classified as a Power Line filter rather than Signal Line, which may affect suitability depending on circuit application requirements. Both are active products with appropriate compliance ratings.

Not Recommended:

The BBSY00100505101Y00 (Pulse Electronics) operates at 100 Ohms @ 100 MHz and does not meet the mandatory 120 Ohm impedance specification.

Frequently Asked Questions (FAQ)

Q: Can I substitute the Z0402C121CSMST with any of the listed alternatives without PCB modification?

A: The 7427927112 and 74279271 (Würth Elektronik) are direct substitutes with identical 0.022" (0.55mm) maximum height and 0402 (1005 Metric) package dimensions. No PCB modification is required. Other alternatives have increased height (0.024" to 0.026") and require verification of available clearance above the component location.

Q: What is the significance of the "Filter Type" parameter?

A: Filter Type indicates the intended application circuit classification. Signal Line ferrite beads are optimized for signal integrity in data and control lines. Power Line beads are designed for power distribution circuits. The HPZ1005U121-R60TF is classified as Power Line and may exhibit different frequency response characteristics compared to the original Signal Line designation.

Q: Are all substitute parts RoHS3 compliant?

A: All listed substitute parts are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity ratings, matching the environmental compliance profile of the original Z0402C121CSMST.

Q: What does "DC Resistance (DCR)" represent, and why is lower DCR preferable?

A: DC Resistance is the resistive loss through the ferrite bead at direct current. Lower DCR reduces power dissipation and heat generation in the component. Substitute parts with DCR equal to or lower than the original 450mOhm specification are acceptable and often provide improved thermal performance.

Q: Can I use a substitute with higher current rating than the original 350mA specification?

A: Yes. Substitute parts with equal or greater current rating are acceptable. Higher current ratings indicate the component can safely handle the original circuit current with additional margin. This does not affect electrical performance at the specified operating current.

Q: What is the difference between "Tape & Reel (TR)" and "Cut Tape (CT) & Digi-Reel®" packaging?

A: Tape & Reel (TR) is continuous reel packaging for automated pick-and-place assembly. Cut Tape (CT) & Digi-Reel® is pre-cut tape supplied on a reel, suitable for lower-volume or mixed-component assembly. Both packaging formats contain identical components; the difference is in supply format and handling for assembly operations.

Q: Is the height difference between 0.022" and 0.026" significant for my application?

A: Height variation of 0.004" (0.10mm) is significant only if the PCB layout has minimal clearance above the component location or if the assembly process uses height-sensitive placement equipment. Verify available clearance in the specific PCB design before selecting a substitute with increased height.

Q: Why is the original Z0402C121CSMST marked as obsolete?

A: Obsolescence indicates the manufacturer (KEMET) has discontinued production. Active substitute parts from alternative manufacturers provide equivalent electrical and mechanical performance while ensuring ongoing availability for new production and field repairs.

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