SA51 Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SA51 is a unidirectional Zener-type transient voltage suppressor diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection applications. The device features a 51V reverse standoff voltage with an 86.52V maximum clamping voltage and 6.2A peak pulse current capability in a through-hole DO-204AC (DO-15) axial package. The SA51 is currently classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and component procurement.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	51V
Voltage - Breakdown (Min)	53.73V
Voltage - Clamping (Max) @ Ipp	86.52V
Current - Peak Pulse (10/1000µs)	6.2A
Power - Peak Pulse	500W
Mounting Type	Through Hole
Package / Case	DO-204AC, DO-15, Axial
Operating Temperature Range	-55°C ~ 175°C (TJ)
Type	Zener
Unidirectional Channels	1

Substitute Part Grouping Explanation

Substitute parts for the SA51 are qualified based on the following critical parameters that determine functional equivalence:

Voltage - Reverse Standoff (Typ): 51V
Voltage - Clamping (Max) @ Ipp: Maximum 86.52V
Current - Peak Pulse (10/1000µs): Minimum 6.1A
Power - Peak Pulse: 500W
Mounting Type: Through Hole
Package / Case: DO-204AC, DO-15, Axial
Type: Zener, Unidirectional (1 channel)

Substitute parts are grouped into two categories: direct manufacturer equivalents from Taiwan Semiconductor Corporation (SA51A) and manufacturer-recommended alternatives from Micro Commercial Co (P5KE51A and SA51A variants with packaging designators).

Parameter Comparison

Parameter	SA51 (Littelfuse)	SA51A (Taiwan Semi)	P5KE51A-AP (MCC)	P5KE51A-BP (MCC)	P5KE51A-TP (MCC)	SA51A-AP (MCC)	SA51A-BP (MCC)	SA51A-TP (MCC)
Voltage - Reverse Standoff (Typ)	51V	51V	51V	51V	51V	51V	51V	51V
Voltage - Breakdown (Min)	53.73V	56.7V	56.7V	56.7V	56.7V	56.7V	56.7V	56.7V
Voltage - Clamping (Max) @ Ipp	86.52V	82.4V	82.4V	82.4V	82.4V	82.4V	82.4V	82.4V
Current - Peak Pulse (10/1000µs)	6.2A	6.3A	6.1A	6.1A	6.1A	6.2A	6.2A	6.2A
Power - Peak Pulse	500W	500W	500W	500W	500W	500W	500W	500W
Operating Temperature Range	-55°C ~ 175°C	-55°C ~ 175°C	-65°C ~ 175°C	-65°C ~ 175°C	-65°C ~ 175°C	-55°C ~ 175°C	-55°C ~ 175°C	-55°C ~ 175°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial
Type	Zener	Zener	Zener	Zener	Zener	Zener	Zener	Zener
Unidirectional Channels	1	1	1	1	1	1	1	1
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified	Not specified	Not specified	Not specified	Not specified	Not specified
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active

Engineering Selection Recommendations

All substitute parts maintain functional equivalence to the SA51 across critical electrical parameters. The primary distinction between substitute options is product status and availability:

SA51A (Taiwan Semiconductor Corporation) is a direct manufacturer equivalent with active product status and ROHS3 compliance, making it the primary substitute for obsolete SA51 applications.

P5KE51A series (Micro Commercial Co) variants—P5KE51A-AP, P5KE51A-BP, and P5KE51A-TP—are manufacturer-recommended alternatives with active status. These parts feature an extended operating temperature range (-65°C to 175°C) compared to the original SA51 specification (-55°C to 175°C), providing additional thermal margin in low-temperature environments.

SA51A series (Micro Commercial Co) variants—SA51A-AP, SA51A-BP, and SA51A-TP—maintain the original operating temperature range (-55°C to 175°C) and are available with active product status. The packaging designators (AP, BP, TP) indicate different supplier packaging configurations (Bulk).

All substitute parts are REACH unaffected and carry EAR99 export classification, matching the compliance profile of the original SA51.

Frequently Asked Questions (FAQ)

Q: Can SA51A from Taiwan Semiconductor Corporation directly replace the Littelfuse SA51?

A: Yes. SA51A maintains identical reverse standoff voltage (51V), equivalent clamping voltage (82.4V vs. 86.52V), and meets or exceeds peak pulse current requirements (6.3A vs. 6.2A). Both are through-hole DO-204AC (DO-15) axial packages with identical mounting characteristics.

Q: What is the difference between P5KE51A and SA51A substitute options?

A: Both maintain the same electrical specifications (51V standoff, 82.4V clamping). The primary difference is operating temperature range: P5KE51A series extends to -65°C minimum, while SA51A series maintains the original -55°C minimum. Peak pulse current differs slightly (6.1A for P5KE51A vs. 6.2A for SA51A).

Q: Do the packaging designators (AP, BP, TP) affect electrical performance?

A: No. The designators (AP, BP, TP) indicate supplier packaging configurations (Bulk) and do not affect electrical characteristics or functional equivalence. Selection should be based on procurement and inventory requirements.

Q: Are all substitute parts RoHS compliant?

A: The SA51A from Taiwan Semiconductor Corporation is explicitly ROHS3 compliant. Micro Commercial Co substitute parts do not specify RoHS status in the provided data; compliance verification should be confirmed with the supplier if RoHS certification is required.

Q: Can I use P5KE51A in applications requiring the original -55°C to 175°C temperature range?

A: Yes. P5KE51A operates within -65°C to 175°C, which encompasses the original -55°C to 175°C specification. The extended low-temperature capability provides additional operational margin.

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