SA15AG Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SA15AG is a unidirectional Zener-type transient voltage suppressor manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in through-hole applications. Specified with a 15V reverse standoff voltage and 24.4V maximum clamping voltage at peak pulse current, this component operates across -55°C to 150°C and is housed in the DO-204AC (DO-15) axial package format.

The SA15AG is classified as obsolete. Identifying functionally equivalent substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications requiring 15V standoff protection with comparable electrical performance.

Key Parameters

Parameter	SA15AG (Main Part)
Manufacturer	Littelfuse Inc.
Type	Zener TVS Diode, Unidirectional
Voltage - Reverse Standoff (Typ)	15V
Voltage - Breakdown (Min)	16.7V
Voltage - Clamping (Max) @ Ipp	24.4V
Current - Peak Pulse (10/1000µs)	20.6A
Power - Peak Pulse	500W
Package / Case	DO-204AC (DO-15), Axial
Mounting Type	Through Hole
Operating Temperature	-55°C ~ 150°C (TJ)
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitute parts for the SA15AG are grouped based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

Voltage - Reverse Standoff: 15V nominal (allows ±0.3V tolerance variance)
Voltage - Clamping (Max) @ Ipp: 24.4V ±0.8V range
Current - Peak Pulse: 20.5A to 21A range (within 2% tolerance)
Power - Peak Pulse: 500W minimum
Package / Case: DO-204AC (DO-15) axial configuration
Mounting Type: Through Hole
Type: Zener, Unidirectional

Substitutes are further categorized by product status (Active vs. Obsolete) and packaging format (Bulk, Tape & Reel, Cut Tape). Parts meeting all electrical parameters within specified tolerances and maintaining identical package geometry are classified as direct equivalents. Parts with higher current ratings or power dissipation in alternative packages are listed as functional alternatives for specific application contexts.

Parameter Comparison

Part Number	Manufacturer	Standoff Voltage (V)	Breakdown Min (V)	Clamp Voltage (V)	Peak Pulse Current (A)	Peak Power (W)	Package	Status	Packaging Format
SA15AG	Littelfuse Inc.	15	16.7	24.4	20.6	500	DO-204AC	Obsolete	-
SA15A	Taiwan Semiconductor Corporation	15	16.7	24.4	21	500	DO-204AC	Active	Tape & Reel
SA15A-B	Littelfuse Inc.	15	16.7	24.4	20.9	500	DO-204AC	Active	Bulk
SA15A-E3/54	Vishay General Semiconductor - Diodes Division	15	16.7	24.4	20.5	500	DO-204AC	Active	Cut Tape
SA15A-TP	Micro Commercial Co	15	16.7	24.4	20.9	500	DO-15	Active	Tape & Reel
SA15AHE3/54	Vishay General Semiconductor - Diodes Division	15	16.7	24.4	20.5	500	DO-204AC	Active	Tape & Reel
SA14A	Fairchild Semiconductor	14	15.6	23.2	22	500	DO-204AC	Obsolete	Bulk
P6KE18A	Fairchild Semiconductor	15.3	17.1	25.2	25	600	DO-15	Active	-
1N8157	Microchip Technology	15	17.1	25.1	5.98	150	Axial	Active	Bulk
SLD15U-017	Littelfuse Inc.	15	16.7	24.4	209	5000	P600	Active	Cut Tape
SLD15U-017-B	Littelfuse Inc.	15	16.7	24.4	209	5000	P600	Active	Bulk

Engineering Selection Recommendations

Direct Electrical Equivalents (Recommended Primary Substitutes)

SA15A, SA15A-B, SA15A-E3/54, SA15A-TP, and SA15AHE3/54 are direct electrical equivalents to the SA15AG. All maintain identical 15V standoff voltage, 16.7V minimum breakdown voltage, and 24.4V maximum clamping voltage specifications. Peak pulse current ratings range from 20.5A to 21A, representing less than 2% variance from the original 20.6A specification. All are rated for 500W peak pulse power and operate within the -55°C to 175°C temperature range, exceeding the SA15AG's -55°C to 150°C specification.

SA15A-B and SA15A-TP are manufactured by Littelfuse Inc. and Micro Commercial Co respectively, both with Active product status and bulk or tape & reel packaging suitable for production environments. SA15A-E3/54 and SA15AHE3/54 from Vishay carry AEC-Q101 automotive qualification, providing additional reliability assurance for critical applications.

Functional Alternatives (Higher Power Capability)

SLD15U-017 and SLD15U-017-B maintain identical voltage specifications (15V standoff, 24.4V clamp) but feature significantly higher current handling (209A peak pulse) and power dissipation (5kW peak pulse) in the P600 package. These are suitable for applications requiring enhanced transient energy absorption while maintaining the same voltage protection threshold. Both carry AEC-Q101 automotive qualification and Active product status.

Marginal Substitutes (Voltage Deviation)

SA14A exhibits a 1V lower standoff voltage (14V vs. 15V) and correspondingly lower clamping voltage (23.2V vs. 24.4V). This part is classified as Obsolete and represents a marginal substitute only when the lower protection threshold is acceptable for the application. P6KE18A operates at 15.3V standoff with 25.2V clamping voltage, representing a 0.3V higher standoff and 0.8V higher clamping specification. This part is Active and suitable when slightly higher voltage thresholds are tolerable.

Limited Substitutes (Reduced Current Capability)

1N8157 from Microchip Technology maintains the 15V standoff voltage but provides only 5.98A peak pulse current and 150W power dissipation. This part is suitable only for low-energy transient suppression applications and is not recommended for general replacement of the SA15AG in standard protection circuits.

Compliance and Certification

All recommended direct equivalents maintain ROHS3 compliance and Moisture Sensitivity Level 1 (Unlimited). Parts with AEC-Q101 qualification (SA15A-E3/54, SA15AHE3/54, SLD15U-017, SLD15U-017-B) are suitable for automotive and mission-critical applications. The SA15AG's Obsolete status necessitates transition to Active-status equivalents; SA15A-B and SA15A-TP provide the most direct replacement path with identical electrical performance and established supply availability.

Frequently Asked Questions (FAQ)

Q: Can SA15A directly replace SA15AG in existing designs?

A: Yes. SA15A maintains identical voltage specifications (15V standoff, 24.4V clamp) and equivalent peak pulse current (21A vs. 20.6A). The primary difference is packaging format (Tape & Reel vs. original specification). Mechanical fit in through-hole applications is identical due to DO-204AC package compatibility. Verify your procurement process accommodates the Tape & Reel format.

Q: What is the difference between SA15A-B and SA15A-TP?

A: Both are electrically identical to SA15AG with 15V standoff and 24.4V clamping voltage. SA15A-B is supplied in Bulk packaging, while SA15A-TP is supplied in Tape & Reel format. Selection depends on assembly process requirements. Bulk packaging is typical for manual or small-batch assembly; Tape & Reel is standard for automated pick-and-place equipment.

Q: Are the Vishay SA15A-E3/54 and SA15AHE3/54 parts interchangeable?

A: Electrically, yes. Both maintain 15V standoff, 24.4V clamping, and 20.5A peak pulse specifications. SA15AHE3/54 carries AEC-Q101 automotive qualification, making it suitable for automotive and high-reliability applications. SA15A-E3/54 is supplied in Cut Tape format; SA15AHE3/54 is supplied in Tape & Reel format. Choose based on assembly process and qualification requirements.

Q: When should I consider SLD15U-017 instead of SA15A?

A: SLD15U-017 maintains identical voltage protection (15V standoff, 24.4V clamp) but provides 209A peak pulse current and 5kW power dissipation versus 21A and 500W for SA15A. Select SLD15U-017 when the circuit experiences high-energy transient events or when multiple transient pulses occur in rapid succession. The P600 package is larger than DO-204AC; verify PCB layout compatibility before substitution.

Q: Is SA14A a suitable replacement for SA15AG?

A: SA14A is not recommended as a primary substitute. It operates at 14V standoff voltage (1V lower than SA15AG) with 23.2V maximum clamping voltage (1.2V lower). This represents a 6.7% reduction in protection threshold. SA14A is also Obsolete. Use SA14A only if application requirements explicitly allow lower voltage protection thresholds and supply constraints prevent access to SA15A or equivalent parts.

Q: What does "Peak Pulse (10/1000µs)" mean in the current specification?

A: This denotes the peak pulse current rating under a specific transient waveform: 10 microseconds rise time and 1000 microseconds decay time. This standardized pulse shape (per IEC 61000-4-5) simulates typical ESD and surge transient events. All substitute parts listed use identical pulse specifications, ensuring direct electrical comparison.

Q: Can I use 1N8157 as a cost-effective alternative?

A: 1N8157 maintains 15V standoff voltage but provides only 5.98A peak pulse current and 150W power dissipation. This represents a 71% reduction in current handling capability compared to SA15AG's 20.6A. Use 1N8157 only in low-energy transient suppression circuits where peak pulse currents remain below 6A. For standard general-purpose protection applications, SA15A or equivalent parts are required.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended direct equivalents (SA15A, SA15A-B, SA15A-E3/54, SA15A-TP, SA15AHE3/54) are ROHS3 compliant. SLD15U-017 and SLD15U-017-B are also ROHS3 compliant. 1N8157 is RoHS non-compliant. Verify RoHS compliance requirements for your application before final part selection.

Q: What is the temperature operating range difference between SA15AG and its substitutes?

A: SA15AG operates from -55°C to 150°C (TJ). Most substitute parts (SA15A, SA15A-B, SA15A-E3/54, SA15A-TP, SA15AHE3/54, SLD15U-017, SLD15U-017-B) extend to -55°C to 175°C, providing 25°C additional high-temperature margin. This expanded range enhances reliability in elevated-temperature environments. 1N8157 also operates to 175°C. This specification improvement is a benefit of transitioning from the obsolete SA15AG.

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