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SA12ARLG Equivalent & Substitute Parts
Part Overview
The SA12ARLG is a 12V Transient Voltage Suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in through-hole applications. This component features a 19.9V maximum clamping voltage and 25.1A peak pulse current capability in a DO-204AC (DO-15) axial package. The part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Voltage - Reverse Standoff (Typ) | 12V |
| Voltage - Breakdown (Min) | 13.3V |
| Voltage - Clamping (Max) @ Ipp | 19.9V |
| Current - Peak Pulse (10/1000µs) | 25.1A |
| Power - Peak Pulse | 500W |
| Package / Case | DO-204AC, DO-15, Axial |
| Mounting Type | Through Hole |
| Operating Temperature | -55°C ~ 150°C (TJ) |
| Type | Zener |
| Unidirectional Channels | 1 |
Substitute Part Grouping Explanation
Substitution eligibility for the SA12ARLG is determined by the following critical parameters:
- Voltage - Reverse Standoff: 12V (exact match required)
- Voltage - Clamping (Max) @ Ipp: 19.9V (exact match required)
- Voltage - Breakdown (Min): 13.3V (exact match required)
- Current - Peak Pulse (10/1000µs): minimum 25.1A
- Package / Case: DO-204AC, DO-15, or equivalent axial through-hole packages
- Mounting Type: Through Hole
- Type: Zener, Unidirectional (1 channel)
Substitute parts are grouped into two categories based on current handling capacity:
Category A: Standard Current Rating (25.1A - 25.6A) Parts with peak pulse current ratings matching or exceeding the original specification while maintaining identical voltage parameters and compatible packaging.
Category B: Enhanced Current Rating (>250A) Parts with significantly higher peak pulse current capability (256.3A or 251.26A) and proportionally increased power dissipation (5000W), suitable for applications requiring higher transient energy absorption while maintaining voltage compatibility.
Parameter Comparison
| Part Number | Manufacturer | Voltage Standoff (V) | Voltage Breakdown Min (V) | Voltage Clamp Max (V) | Current Peak Pulse (A) | Power Peak Pulse (W) | Package | Status |
|---|---|---|---|---|---|---|---|---|
| SA12ARLG | Littelfuse Inc. | 12 | 13.3 | 19.9 | 25.1 | 500 | DO-204AC (DO-15) | Obsolete |
| SA12A | Fairchild Semiconductor | 12 | 13.3 | 19.9 | 25.1 | 500 | DO-15 | Obsolete |
| SA12A-B | Littelfuse Inc. | 12 | 13.3 | 19.9 | 25.6 | 500 | DO-204AC (DO-15) | Active |
| SA12A-E3/54 | Vishay General Semiconductor | 12 | 13.3 | 19.9 | 25.1 | 500 | DO-204AC (DO-15) | Active |
| SA12A-TP | Micro Commercial Co | 12 | 13.3 | 19.9 | 25.6 | 500 | DO-15 | Active |
| SA12AHE3/54 | Vishay General Semiconductor | 12 | 13.3 | 19.9 | 25.1 | 500 | DO-204AC (DO-15) | Active |
| SAC12-AP | Micro Commercial Co | 12 | 13.3 | 19 | 25 | 500 | DO-15 | Active |
| SLD12U-017 | Littelfuse Inc. | 12 | 13.3 | 19.9 | 256.3 | 5000 | P600 | Active |
| SLD12U-017-B | Littelfuse Inc. | 12 | 13.3 | 19.9 | 256.3 | 5000 | P600 | Active |
| 5KP12A-G | Comchip Technology | 12 | 13.3 | 19.9 | 251.26 | 5000 | R-6 | Active |
| 1N8155 | Microchip Technology | 12 | 13.8 | 20.2 | 7.42 | 150 | Axial | Active |
Engineering Selection Recommendations
Primary Substitutes (Recommended for Direct Replacement)
SA12A-B, SA12A-E3/54, SA12A-TP, and SA12AHE3/54 are the preferred substitutes. These parts maintain identical voltage specifications (12V standoff, 13.3V breakdown minimum, 19.9V clamping maximum) and equivalent current ratings (25.1A to 25.6A). All are active products with ROHS3 compliance and REACH unaffected status. SA12A-B and SA12AHE3/54 include AEC-Q101 automotive qualification, providing additional reliability assurance. These parts are available in compatible DO-204AC (DO-15) or DO-15 packages suitable for through-hole PCB mounting.
Alternative Substitutes (Higher Current Capacity)
SLD12U-017, SLD12U-017-B, and 5KP12A-G provide enhanced transient energy absorption with peak pulse currents of 256.3A and 251.26A respectively, and 5000W power dissipation. These parts maintain voltage compatibility but require different package footprints (P600 and R-6 respectively). Selection of these alternatives is appropriate only when circuit design accommodates the larger package dimensions and when higher transient energy absorption is required.
Not Recommended
1N8155 exhibits voltage parameter deviations (13.8V breakdown minimum, 20.2V clamping maximum) and significantly reduced current capacity (7.42A), making it unsuitable as a direct replacement. Additionally, this part carries RoHS non-compliant status.
SAC12-AP presents marginal voltage and current deviations (19V clamping, 25A peak pulse) that fall outside strict equivalence criteria.
Frequently Asked Questions (FAQ)
Q: Can SA12A-B be used as a direct replacement for SA12ARLG?
A: Yes. SA12A-B maintains all critical voltage parameters (12V standoff, 13.3V breakdown, 19.9V clamping) and meets or exceeds the current requirement (25.6A vs. 25.1A). The part is active, ROHS3 compliant, and available in the compatible DO-204AC (DO-15) package. Operating temperature range extends to 175°C, exceeding the original specification.
Q: What is the difference between Category A and Category B substitutes?
A: Category A substitutes (SA12A-B, SA12A-E3/54, SA12A-TP, SA12AHE3/54) maintain the original 500W power rating and 25.1A–25.6A current capacity, providing direct functional equivalence. Category B substitutes (SLD12U-017, SLD12U-017-B, 5KP12A-G) offer 5000W power dissipation and 251–256A peak pulse current, designed for applications requiring higher transient energy absorption. Category B parts require different package footprints and should be selected only when circuit design supports the larger dimensions and higher current handling is necessary.
Q: Are there compliance or qualification differences between substitute options?
A: SA12AHE3/54 and SLD12U-017 series include AEC-Q101 automotive qualification, suitable for automotive and high-reliability applications. SA12A-E3/54 and SA12A-TP are active products with standard industrial compliance. All recommended Category A substitutes carry ROHS3 compliance and REACH unaffected status. 1N8155 is RoHS non-compliant and should not be selected for new designs requiring regulatory compliance.
Q: Can I use a higher current-rated part (Category B) in place of the original SA12ARLG?
A: Electrical substitution is valid if circuit design accommodates the different package footprint. SLD12U-017 series uses P600 package; 5KP12A-G uses R-6 package. Both maintain voltage compatibility. However, PCB layout modifications are required, and component mounting must be verified for mechanical fit. Selection should be driven by application requirements for higher transient energy absorption, not as a general upgrade.
Q: Why is 1N8155 not recommended?
A: 1N8155 deviates from critical voltage parameters (13.8V breakdown minimum vs. 13.3V required; 20.2V clamping maximum vs. 19.9V required) and provides insufficient current capacity (7.42A vs. 25.1A minimum). The part is also RoHS non-compliant. These factors make it unsuitable for direct replacement.
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