SA18ARL Equivalent & Substitute Parts

Part Overview

The SA18ARL is a unidirectional Transient Voltage Suppressor (TVS) diode manufactured by onsemi, designed for general-purpose overvoltage protection applications. This component features an 18V reverse standoff voltage with a 29.2V maximum clamping voltage and 17.2A peak pulse current capability. The SA18ARL is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing design support and component procurement.

Substiute Parts

SA18ARL

onsemiIn Stock: 1106SA18ARL Datasheet

Current PartRFQ

SA18A

Fairchild SemiconductorIn Stock: 7654SA18A Datasheet

DirectRFQ

1N8159

Microchip TechnologyIn Stock: 10571N8159 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the SA18ARL is determined by the following critical parameters:

• Voltage - Reverse Standoff (Typ): 18V
• Voltage - Clamping (Max) @ Ipp: 29.2V maximum
• Current - Peak Pulse (10/1000µs): minimum 17.2A
• Package / Case: DO-204AC, DO-15, or Axial through-hole
• Type: Zener unidirectional TVS diode

The SA18A qualifies as a direct substitute, meeting all electrical specifications and package requirements. The 1N8159 is classified as a similar alternative; however, it exhibits reduced peak pulse current capability (4.92A versus 17.2A required), which may limit its suitability for applications requiring the full current handling capacity of the original design.

Parameter Comparison

Engineering Selection Recommendations

The SA18A represents the optimal substitute for the SA18ARL. Both components share identical electrical specifications for reverse standoff voltage, clamping voltage, and peak pulse current. The SA18A maintains the same 500W peak pulse power rating and through-hole axial package configuration. Additionally, the SA18A offers an extended operating temperature range (-55°C ~ 175°C versus -55°C ~ 150°C) and achieves ROHS3 compliance, providing advantages for modern manufacturing and environmental standards.

The 1N8159 maintains voltage compatibility but exhibits significantly reduced current handling capacity (4.92A peak pulse current). This component is suitable only for applications where peak pulse current requirements do not exceed 4.92A. The 1N8159 is currently in active production status, offering long-term availability advantages.

Frequently Asked Questions (FAQ)

Q: Can the SA18A directly replace the SA18ARL in existing designs?

A: Yes. The SA18A meets all electrical specifications of the SA18ARL, including reverse standoff voltage (18V), clamping voltage (29.2V), and peak pulse current (17.5A). Both components use identical through-hole axial packaging. The SA18A provides additional benefits through extended temperature range and RoHS3 compliance.

Q: What is the primary limitation of the 1N8159 as a substitute?

A: The 1N8159 exhibits reduced peak pulse current capability (4.92A) compared to the SA18ARL requirement (17.2A). This component is suitable only for applications with lower current transient events. The power dissipation is also reduced to 150W versus 500W.

Q: Are there package compatibility concerns between these parts?

A: The SA18A and SA18ARL share identical DO-204AC (DO-15) axial through-hole packaging, ensuring direct mechanical compatibility. The 1N8159 uses axial packaging but may have different physical dimensions; verification against PCB footprint specifications is necessary.

Q: Does RoHS compliance affect substitution decisions?

A: The SA18A achieves ROHS3 compliance, while both the SA18ARL and 1N8159 are RoHS non-compliant. For applications subject to RoHS requirements, the SA18A is the preferred choice. For legacy systems without RoHS mandates, all three components remain viable based on electrical requirements.

Q: What is the temperature operating range difference?

A: The SA18ARL operates from -55°C to 150°C (TJ), while the SA18A and 1N8159 extend to -55°C to 175°C (TJ). For applications operating near upper temperature limits, the SA18A and 1N8159 provide additional thermal margin.