SG312 Inrush Current Limiter - Equivalent & Substitute Parts

Part Overview

The SG312 is an 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 SG312 operates at 7 Ohms with ±15% tolerance and supports a steady-state maximum current of 4 A. The part is currently active in production with full inventory availability (1061 pcs in stock). Finding equivalent or substitute parts may be necessary due to supply chain considerations, lead time requirements, or specific application constraints.

Substiute Parts

SG312

AmethermIn Stock: 1099SG312 Datasheet

Current PartRFQ

B57238S0709M000

EPCOS - TDK ElectronicsIn Stock: 1764B57238S0709M000 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for inrush current limiters is determined by the following critical parameters:

• Nominal Resistance Value: Must match at 7 Ohms
• Tolerance Range: Acceptable tolerance must not exceed application requirements
• Steady State Current Rating: Must meet or exceed the 4 A requirement
• Physical Package Dimensions: Lead spacing and diameter must accommodate PCB layout constraints
• Regulatory Compliance: RoHS3 compliance and approval agency certifications must be maintained

The B57238S0709M000 (EPCOS - TDK Electronics) qualifies as a substitute based on matching the 7 Ohm nominal resistance and exceeding the current rating specification. Tolerance and package dimensions differ within acceptable engineering margins for most applications.

Parameter Comparison

Engineering Selection Recommendations

Both the SG312 and B57238S0709M000 maintain ROHS3 compliance and are active production components. The B57238S0709M000 provides a higher steady-state current rating (6 A versus 4 A), which offers additional thermal margin in applications operating near the SG312's maximum specification. The tolerance difference (±20% versus ±15%) and package dimension variations must be evaluated against specific circuit requirements and PCB layout constraints. Both components carry appropriate regulatory approvals for industrial and commercial applications.

Frequently Asked Questions (FAQ)

Q: Can the B57238S0709M000 directly replace the SG312 in all applications?

A: Direct replacement depends on application-specific requirements. The B57238S0709M000 matches the 7 Ohm nominal resistance and exceeds the current rating. However, the wider tolerance (±20% versus ±15%) and different package dimensions (0.630" diameter and 0.295" lead spacing versus 0.600" diameter and 0.350" lead spacing) must be verified against circuit design specifications and PCB layout constraints.

Q: What is the significance of the tolerance difference between these parts?

A: The SG312 specifies ±15% tolerance while the B57238S0709M000 specifies ±20% tolerance. This means the B57238S0709M000 resistance value may deviate further from the nominal 7 Ohm specification. Applications with tight inrush current control requirements should evaluate whether the wider tolerance is acceptable.

Q: Are there physical compatibility concerns with the different package dimensions?

A: Yes. The B57238S0709M000 has a slightly larger diameter (0.630" versus 0.600") and different lead spacing (0.295" versus 0.350"). PCB footprints and mechanical clearances must be verified before substitution to ensure proper fit and assembly.

Q: Do both parts meet the same regulatory requirements?

A: Both parts are ROHS3 compliant and suitable for applications requiring regulatory compliance in this category. The SG312 carries CSA and UR approvals. Specific application certifications should be confirmed with the end-use equipment manufacturer.

Q: Why would I choose the B57238S0709M000 over the SG312?

A: The B57238S0709M000 may be selected based on supply availability, lead time, or the higher 6 A current rating if additional thermal margin is beneficial for the application. Inventory availability (1748 pcs) also exceeds the SG312 stock level.