SG304 Inrush Current Limiter - Equivalent & Substitute Parts

Part Overview

The SG304 is an active inrush current limiter manufactured by Ametherm, part of the SURGE-GARD™ series. This component is designed to limit inrush current in power supply circuits and related applications. The device operates at 2.5 Ohms resistance with a maximum steady-state current rating of 7 A and is housed in a 0.600" (15.24mm) diameter package. The SG304 maintains active product status and is ROHS3 compliant with CSA and UR approvals. Alternative models are identified when inventory constraints occur or when application requirements permit tolerance or current rating variations within acceptable engineering parameters.

Substiute Parts

SG304

AmethermIn Stock: 1049SG304 Datasheet

Current PartRFQ

B57238S0259M000

EPCOS - TDK ElectronicsIn Stock: 12729B57238S0259M000 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

The B57238S0259M000 (EPCOS - TDK Electronics) qualifies as a substitute for the SG304 based on the following critical parameters:

• Resistance Value: Both parts maintain 2.5 Ohms nominal resistance, the primary functional parameter for inrush current limiting applications
• Steady-State Current Rating: The substitute part is rated for 8.4 A maximum steady-state current, which exceeds the SG304's 7 A rating, providing operational margin
• Tolerance: The substitute operates at ±20% tolerance compared to the SG304's ±15%, representing a wider but acceptable variance for this component category
• Package Diameter: The substitute measures 0.630" (16.00mm) compared to the SG304's 0.600" (15.24mm), a 0.030" difference that may require mechanical clearance verification in constrained layouts
• Lead Spacing: The substitute provides 0.295" (7.50mm) spacing versus 0.310" (7.87mm), a minor dimensional variation
• Regulatory Compliance: Both parts are ROHS3 compliant and maintain active product status

Parameter Comparison

Engineering Selection Recommendations

Selection between the SG304 and B57238S0259M000 depends on application-specific constraints:

Choose SG304 when:

• Tighter tolerance specification (±15%) is required for circuit performance
• Mechanical envelope is constrained to 0.600" diameter maximum
• Lead spacing of 0.310" is required for PCB layout compatibility
• CSA and UR certifications are specifically mandated

Choose B57238S0259M000 when:

• Higher steady-state current margin (8.4 A vs. 7 A) provides operational headroom
• Wider tolerance (±20%) is acceptable for the application
• Mechanical space permits the 0.630" diameter package
• UL certification satisfies regulatory requirements
• EPCOS - TDK Electronics supply chain availability is preferred

Both parts maintain ROHS3 compliance and active manufacturing status, ensuring long-term availability and regulatory alignment.

Frequently Asked Questions (FAQ)

Q: Can B57238S0259M000 directly replace SG304 in all applications?

A: Direct replacement requires verification of three factors: (1) mechanical clearance for the 0.030" larger diameter, (2) PCB layout accommodation of the 0.015" closer lead spacing, and (3) circuit tolerance of the ±20% resistance variance versus the original ±15% specification.

Q: What is the significance of the 7 A versus 8.4 A current rating difference?

A: The B57238S0259M000's higher 8.4 A rating indicates greater thermal capacity and current-handling capability. This provides operational margin but does not change the fundamental inrush current limiting function at equivalent resistance values.

Q: Are there mechanical considerations for PCB mounting?

A: Yes. The substitute part's 0.630" diameter is 0.030" larger than the SG304, and lead spacing differs by 0.015". Verify that PCB footprints, mounting holes, and component clearances accommodate these dimensional variations before implementation.

Q: Do both parts meet the same regulatory standards?

A: Both are ROHS3 compliant. The SG304 carries CSA and UR approvals, while the B57238S0259M000 carries UL approval. Verify that your application's specific regulatory requirements are satisfied by the selected part's certification.

Q: What tolerance impact should be expected when substituting?

A: The SG304 operates within ±15% of nominal 2.5 Ohms (2.125 to 2.875 Ohms). The B57238S0259M000 operates within ±20% (2.0 to 3.0 Ohms). Circuit designs must accommodate the wider tolerance band of the substitute part.