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SA12AG Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts
Part Overview
The SA12AG is a unidirectional Transient Voltage Suppressor (TVS) diode manufactured by Littelfuse, classified as a MiniMosorb™ series component. This through-hole axial device operates with a 12V reverse standoff voltage and provides 19.9V maximum clamping voltage at peak pulse current of 25.1A. The SA12AG is designated as obsolete, necessitating identification of active equivalent and substitute parts that maintain electrical and mechanical compatibility for general-purpose transient voltage suppression applications.
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 |
| Mounting Type | Through Hole |
| Package / Case | DO-204AC (DO-15), Axial |
| Operating Temperature Range | -55°C ~ 150°C (TJ) |
| Type | Zener |
| Unidirectional Channels | 1 |
| RoHS Status | ROHS3 Compliant |
Substitute Part Grouping Explanation
Substitution of the SA12AG is determined by strict adherence to the following electrical and mechanical parameters:
Critical Matching Parameters:
- Voltage - Reverse Standoff: 12V
- Voltage - Breakdown (Min): 13.3V
- Voltage - Clamping (Max) @ Ipp: 19.9V
- Type: Zener, Unidirectional (1 channel)
- Mounting Type: Through Hole, Axial orientation
- Package / Case: DO-204AC (DO-15) or equivalent axial package
Acceptable Variation Parameters:
- Current - Peak Pulse (10/1000µs): 25.1A minimum (higher values acceptable for same voltage class)
- Power - Peak Pulse: 500W minimum (higher values acceptable)
- Operating Temperature Range: -55°C minimum to 150°C minimum (extended ranges acceptable)
- Product Status: Active preferred over obsolete
Substitute parts are grouped into two categories:
Category A - Direct Electrical & Package Equivalents (DO-15/DO-204AC): Parts maintaining identical voltage specifications, peak pulse current within 25.1A to 25.6A range, 500W power rating, and DO-15/DO-204AC package format. These provide pin-for-pin and functional equivalence.
Category B - Enhanced Performance Substitutes (P600/R-6 Package): Parts maintaining identical voltage specifications with significantly higher peak pulse current (251.26A to 256.3A) and 5000W power rating. These use alternative through-hole axial packages (P600, R-6) and provide superior transient suppression capability while maintaining electrical compatibility at the 12V voltage class.
Category C - Reduced Performance Substitute: Parts with identical voltage specifications but lower peak pulse current (7.42A) and 150W power rating. Suitable only for applications with reduced transient energy requirements.
Parameter Comparison
| Part Number | Manufacturer | Voltage - Reverse Standoff | Voltage - Clamping (Max) @ Ipp | Current - Peak Pulse (10/1000µs) | Power - Peak Pulse | Package / Case | Operating Temperature | Product Status | RoHS Status |
|---|---|---|---|---|---|---|---|---|---|
| SA12AG | Littelfuse | 12V | 19.9V | 25.1A | 500W | DO-204AC (DO-15) | -55°C ~ 150°C | Obsolete | ROHS3 Compliant |
| SA12A | Fairchild Semiconductor | 12V | 19.9V | 25.1A | 500W | DO-15 | Not specified | Obsolete | ROHS3 Compliant |
| SA12A-B | Littelfuse Inc. | 12V | 19.9V | 25.6A | 500W | DO-204AC (DO-15) | -55°C ~ 175°C | Active | ROHS3 Compliant |
| SA12A-E3/54 | Vishay General Semiconductor - Diodes Division | 12V | 19.9V | 25.1A | 500W | DO-204AC (DO-15) | -55°C ~ 175°C | Active | ROHS3 Compliant |
| SA12A-TP | Micro Commercial Co | 12V | 19.9V | 25.6A | 500W | DO-15 | -55°C ~ 175°C | Active | ROHS3 Compliant |
| SA12AHE3/54 | Vishay General Semiconductor - Diodes Division | 12V | 19.9V | 25.1A | 500W | DO-204AC (DO-15) | -55°C ~ 175°C | Active | ROHS3 Compliant |
| SAC12-AP | Micro Commercial Co | 12V | 19V | 25A | 500W | DO-15 | -55°C ~ 175°C | Active | Not specified |
| SLD12U-017 | Littelfuse Inc. | 12V | 19.9V | 256.3A | 5000W | P600 | -55°C ~ 175°C | Active | ROHS3 Compliant |
| SLD12U-017-B | Littelfuse Inc. | 12V | 19.9V | 256.3A | 5000W | P600 | -55°C ~ 175°C | Active | ROHS3 Compliant |
| 5KP12A-G | Comchip Technology | 12V | 19.9V | 251.26A | 5000W | R-6 | -55°C ~ 150°C | Active | ROHS3 Compliant |
| 1N8155 | Microchip Technology | 12V | 20.2V | 7.42A | 150W | Axial | -55°C ~ 175°C | Active | RoHS non-compliant |
Engineering Selection Recommendations
Primary Substitutes (Direct Equivalence):
SA12A-B, SA12A-E3/54, SA12A-TP, and SA12AHE3/54 are the preferred substitutes for SA12AG replacement. All four parts maintain identical 12V reverse standoff voltage, 19.9V clamping voltage, and 500W peak pulse power rating. These parts are active products with ROHS3 compliance and extended operating temperature ranges (-55°C ~ 175°C), providing superior long-term availability and environmental compliance compared to the obsolete SA12AG. SA12A-B and SA12A-TP offer marginally higher peak pulse current (25.6A vs. 25.1A), providing additional transient suppression margin. SA12A-E3/54 and SA12AHE3/54 are qualified to AEC-Q101 automotive standards, suitable for applications requiring automotive-grade reliability.
Secondary Substitutes (Enhanced Performance):
SLD12U-017, SLD12U-017-B, and 5KP12A-G maintain identical voltage specifications while providing 10-fold increase in peak pulse current (251.26A to 256.3A) and 5000W peak pulse power rating. These parts use alternative through-hole axial packages (P600 and R-6 respectively) and are suitable for applications experiencing higher transient energy levels. SLD12U-017 and SLD12U-017-B carry AEC-Q101 automotive qualification. Package change requires PCB layout verification for mechanical fit.
Tertiary Substitute (Reduced Performance):
1N8155 maintains 12V voltage class specifications but provides only 7.42A peak pulse current and 150W power rating. This part is suitable only for applications with minimal transient energy requirements. 1N8155 is RoHS non-compliant and should be avoided in new designs requiring environmental compliance.
Not Recommended:
SA12A (Fairchild Semiconductor) is obsolete with unspecified operating temperature range, limiting its utility for replacement applications.
SAC12-AP exhibits marginal clamping voltage deviation (19V vs. 19.9V) and reduced peak pulse current (25A vs. 25.1A), representing suboptimal electrical matching.
Frequently Asked Questions (FAQ)
Q: Can SA12A-B directly replace SA12AG without PCB modification?
A: Yes. SA12A-B maintains identical voltage specifications (12V reverse standoff, 19.9V clamping) and uses the same DO-204AC (DO-15) axial package as SA12AG. No PCB layout changes are required. The marginal increase in peak pulse current (25.6A vs. 25.1A) provides additional transient suppression capability without affecting circuit operation.
Q: What is the difference between DO-15 and DO-204AC package designations?
A: DO-15 and DO-204AC are equivalent package designations for the same through-hole axial diode package. Both refer to a cylindrical component with axial leads suitable for through-hole PCB mounting. Parts specified as either DO-15 or DO-204AC are mechanically and electrically interchangeable.
Q: Can SLD12U-017 replace SA12AG in existing designs?
A: SLD12U-017 maintains identical voltage specifications and provides superior transient suppression capability (256.3A peak pulse current vs. 25.1A). However, SLD12U-017 uses the P600 package, which differs mechanically from SA12AG's DO-15 package. PCB layout verification is required to confirm mechanical fit before substitution. Electrical compatibility is confirmed.
Q: Why is 1N8155 not recommended as a substitute?
A: 1N8155 provides only 7.42A peak pulse current and 150W power rating, representing a 97% reduction in transient suppression capability compared to SA12AG's 25.1A and 500W specifications. Additionally, 1N8155 is RoHS non-compliant. This part is suitable only for applications with significantly reduced transient energy requirements and should not be used in new designs.
Q: Are automotive-qualified substitutes available?
A: Yes. SA12AHE3/54 and SLD12U-017 (and SLD12U-017-B) carry AEC-Q101 automotive qualification. Both maintain identical 12V voltage class specifications and are suitable for automotive and mission-critical applications requiring automotive-grade reliability certification.
Q: What is the inventory status of substitute parts?
A: Active substitute parts with highest inventory availability are SA12A-E3/54 (21,162 pcs), SA12A-TP (906 pcs), SA12A-B (1,689 pcs), and SLD12U-017-B (1,148 pcs). These parts are recommended for immediate procurement to ensure supply chain continuity.
Q: Can multiple substitute parts be used interchangeably in the same design?
A: Yes, within their respective performance categories. All Category A substitutes (SA12A-B, SA12A-E3/54, SA12A-TP, SA12AHE3/54) are electrically and mechanically interchangeable with SA12AG. Category B substitutes (SLD12U-017, SLD12U-017-B, 5KP12A-G) are electrically compatible but require package-specific PCB layout verification. Do not mix Category A and Category B parts in the same design without confirming mechanical fit.
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