SA18A-E3/54 Equivalent & Substitute Parts

Part Overview

The SA18A-E3/54 is a unidirectional Transient Voltage Suppressor (TVS) diode manufactured by Vishay General Semiconductor - Diodes Division. This through-hole component operates with an 18V reverse standoff voltage and provides 29.2V maximum clamping voltage at peak pulse current. The device is designed for general-purpose transient voltage suppression applications and is currently in active production status with ROHS3 compliance.

Equivalent and substitute parts are necessary when the primary component becomes unavailable, when alternative packaging or performance characteristics better suit specific application requirements, or when supply chain optimization is needed while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	18V
Voltage - Breakdown (Min)	20V
Voltage - Clamping (Max) @ Ipp	29.2V
Current - Peak Pulse (10/1000µs)	17.1A
Power - Peak Pulse	500W
Operating Temperature Range	-55°C to 175°C (TJ)
Mounting Type	Through Hole
Package / Case	DO-204AC (DO-15), Axial
Type	Zener
Unidirectional Channels	1

Substitute Part Grouping Explanation

Substitute parts for the SA18A-E3/54 are qualified based on the following critical parameters that determine functional equivalence:

Voltage - Reverse Standoff: 18V (exact match required)
Voltage - Breakdown (Min): 20V (exact match required)
Voltage - Clamping (Max) @ Ipp: 29.2V or lower (acceptable within tolerance)
Current - Peak Pulse: 17.1A or higher (acceptable if equal or greater)
Power - Peak Pulse: 500W or higher (acceptable if equal or greater)
Operating Temperature Range: -55°C to 175°C (exact match required)
Mounting Type: Through Hole (exact match required)
Package / Case: DO-204AC (DO-15) or compatible axial packages
Type: Zener, Unidirectional (exact match required)

Three substitute parts meet these criteria with varying performance characteristics and availability status.

Parameter Comparison

Parameter	SA18A-E3/54 (Main)	SA18A (Fairchild)	SAC18 (Littelfuse)	LCE18A (Littelfuse)
Manufacturer	Vishay	Fairchild Semiconductor	Littelfuse	Littelfuse Inc.
Voltage - Reverse Standoff (Typ)	18V	18V	18V	18V
Voltage - Breakdown (Min)	20V	20V	20V	20V
Voltage - Clamping (Max) @ Ipp	29.2V	29.2V	28.8V	29.2V
Current - Peak Pulse (10/1000µs)	17.1A	17.5A	15A	51A
Power - Peak Pulse	500W	500W	500W	1500W
Operating Temperature Range	-55°C to 175°C	-55°C to 175°C	-55°C to 175°C	-55°C to 175°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	DO-204AC (DO-15)	DO-204AC (DO-15)	DO-204AC (DO-15)	DO-201AA (DO-27)
Product Status	Active	Obsolete	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

SA18A (Fairchild Semiconductor): This part provides electrical equivalence with marginally higher peak pulse current (17.5A vs. 17.1A) and identical clamping voltage. However, the product status is obsolete, limiting long-term availability and supply chain reliability. Selection should be restricted to applications where existing inventory is available and future restocking is not required.

SAC18 (Littelfuse): This part maintains the same package format (DO-204AC) and operating temperature range. The clamping voltage is slightly lower at 28.8V, and peak pulse current is reduced to 15A. This part is suitable for applications with lower transient current requirements and is actively produced with confirmed ROHS3 compliance and unlimited moisture sensitivity rating.

LCE18A (Littelfuse): This part offers superior performance with 51A peak pulse current and 1500W power dissipation, providing significant margin above the main part specifications. The package format differs (DO-201 instead of DO-204AC), requiring mechanical redesign of the circuit board layout. This part is actively produced and recommended for applications requiring enhanced transient suppression capability or where board space permits the larger package footprint.

Frequently Asked Questions (FAQ)

Q: Can SA18A (Fairchild) be used as a direct replacement for SA18A-E3/54?

A: Electrically, yes. The SA18A provides equivalent voltage ratings and slightly higher peak pulse current (17.5A). However, the obsolete product status presents supply chain risk. Use only if existing inventory is confirmed available.

Q: What is the primary difference between SAC18 and SA18A-E3/54?

A: The SAC18 has a lower peak pulse current rating (15A vs. 17.1A) and slightly lower clamping voltage (28.8V vs. 29.2V). Both use identical DO-204AC packaging. The SAC18 is suitable for applications with lower transient current demands.

Q: Why does LCE18A use a different package (DO-201 vs. DO-204AC)?

A: The DO-201 package is physically larger and accommodates higher power dissipation (1500W vs. 500W). This allows the LCE18A to handle 51A peak pulse current compared to 17.1A in the main part. Package selection depends on circuit board layout constraints and application transient current requirements.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. SA18A, SAC18, and LCE18A all carry ROHS3 compliance certification, matching the main part SA18A-E3/54.

Q: Which substitute part should be selected for new designs?

A: For new designs requiring direct package compatibility, select SAC18 (active status, DO-204AC package). For applications requiring enhanced transient suppression capability, select LCE18A (active status, higher current and power ratings, DO-201 package).

Q: Can SAC18 be used in applications designed for SA18A-E3/54?

A: Yes, provided the application transient current does not exceed 15A. The voltage ratings and operating temperature range are identical. Verify that the 0.4V lower clamping voltage (28.8V vs. 29.2V) is acceptable for the specific circuit protection requirement.

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