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SMAJ18C-E3/5A Equivalent & Substitute Parts
Part Overview
The SMAJ18C-E3/5A is a transient voltage suppressor (TVS) diode manufactured by Vishay General Semiconductor - Diodes Division, designed for general-purpose overvoltage protection in surface-mount applications. This part operates with an 18V reverse standoff voltage and provides 32.2V maximum clamping voltage at peak pulse current. The SMAJ18C-E3/5A is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Reverse Standoff Voltage (Typ) | 18V |
| Breakdown Voltage (Min) | 20V |
| Clamping Voltage (Max) @ Ipp | 32.2V |
| Peak Pulse Current (10/1000µs) | 12.4A |
| Peak Pulse Power | 400W |
| Package / Case | DO-214AC, SMA |
| Mounting Type | Surface Mount |
| Operating Temperature Range | -55°C ~ 150°C (TJ) |
| Type | Zener |
| Bidirectional Channels | 1 |
| RoHS Status | ROHS3 Compliant |
Substitute Part Grouping Explanation
Substitution for the SMAJ18C-E3/5A is determined by the following critical parameters:
- Reverse standoff voltage: 18V (fixed requirement)
- Breakdown voltage minimum: 20V (fixed requirement)
- Package type: DO-214AC / SMA (fixed requirement)
- Mounting type: Surface Mount (fixed requirement)
- Bidirectional channels: 1 (fixed requirement)
- Operating temperature range: minimum -55°C to 150°C (fixed requirement)
- RoHS compliance: ROHS3 (fixed requirement)
Substitute parts are grouped into two categories based on electrical performance:
Category A - Direct Electrical Equivalents: Parts with clamping voltage 29.2V–32.2V and peak pulse current 12.4A–13.7A. These maintain the original circuit protection characteristics.
Category B - Enhanced Performance Alternatives: Parts with higher clamping voltage (33.2V–39.3V) and higher peak pulse current (59A–102A). These provide superior transient suppression but operate within the same voltage class and package footprint.
Parameter Comparison
| Part Number | Manufacturer | Status | Clamping Voltage (Max) @ Ipp | Peak Pulse Current | Peak Pulse Power | Operating Temp Range | Qualification |
|---|---|---|---|---|---|---|---|
| SMAJ18C-E3/5A | Vishay | Obsolete | 32.2V | 12.4A (10/1000µs) | 400W | -55°C ~ 150°C | — |
| SMAJ18CA-E3/5A | Vishay | Active | 29.2V | 13.7A (10/1000µs) | 400W | -55°C ~ 150°C | — |
| SMAJ18C | Taiwan Semiconductor | Active | 32.2V | 12.4A (10/1000µs) | 400W | -55°C ~ 150°C | — |
| ATV04A180JB-HF | Comchip Technology | Active | 29.2V | 13.7A (10/1000µs) | 400W | -55°C ~ 150°C | AEC-Q101 |
| SM4T21CAY | STMicroelectronics | Active | 39.3V | 59A (8/20µs) | 400W | -55°C ~ 150°C | AEC-Q101 |
| SMA6J18CA-TR | STMicroelectronics | Active | 33.2V | 102A (8/20µs) | 600W | -55°C ~ 175°C | — |
| SMAJ18CA-13-F | Diodes Incorporated | Active | 29.2V | 13.7A (10/1000µs) | 400W | -55°C ~ 150°C | — |
| SMAJ18CA | MDD | Active | 29.2V | 13.7A (10/1000µs) | 400W | -50°C ~ 150°C | — |
Engineering Selection Recommendations
Direct Replacement (Category A):
SMAJ18CA-E3/5A (Vishay) is the primary direct replacement. It maintains active product status, identical package and mounting specifications, and equivalent electrical performance within the 18V protection class. Both parts share the same base product number (SMAJ18) and RoHS3 compliance.
SMAJ18C (Taiwan Semiconductor) provides identical electrical characteristics to the original part with active status and full compliance documentation.
SMAJ18CA-13-F (Diodes Incorporated) and SMAJ18CA (MDD) offer electrical equivalence with active status and high inventory availability.
Automotive-Grade Alternative (Category A):
ATV04A180JB-HF (Comchip Technology) is AEC-Q101 qualified and suitable for automotive applications requiring enhanced reliability documentation. Electrical performance is equivalent to Category A parts.
Enhanced Performance Alternatives (Category B):
SM4T21CAY (STMicroelectronics) and SMA6J18CA-TR (STMicroelectronics) provide higher transient suppression capability with increased peak pulse current and clamping voltage. These are suitable for applications requiring superior overvoltage protection margins. Both maintain the same 18V standoff voltage and DO-214AC package compatibility. SMA6J18CA-TR extends the operating temperature range to 175°C and increases peak pulse power to 600W.
Frequently Asked Questions (FAQ)
Q: Can SMAJ18CA-E3/5A directly replace SMAJ18C-E3/5A?
A: Yes. Both parts share identical reverse standoff voltage (18V), breakdown voltage (20V), package type (DO-214AC/SMA), and operating temperature range (-55°C to 150°C). SMAJ18CA-E3/5A has active product status, making it the recommended direct replacement.
Q: What is the difference between Category A and Category B substitutes?
A: Category A parts (SMAJ18CA-E3/5A, SMAJ18C, SMAJ18CA-13-F, SMAJ18CA) maintain the original clamping voltage specification of 29.2V–32.2V and peak pulse current of 12.4A–13.7A. Category B parts (SM4T21CAY, SMA6J18CA-TR) provide higher clamping voltage (33.2V–39.3V) and significantly higher peak pulse current (59A–102A), offering enhanced transient suppression. Both categories are electrically compatible within the 18V protection class.
Q: Are all substitute parts RoHS3 compliant?
A: Yes. All listed substitute parts are ROHS3 compliant, matching the original SMAJ18C-E3/5A specification.
Q: Which substitute is recommended for automotive applications?
A: ATV04A180JB-HF (Comchip Technology) carries AEC-Q101 qualification, making it suitable for automotive-grade designs requiring formal reliability certification.
Q: Can I use SM4T21CAY or SMA6J18CA-TR as direct replacements?
A: These parts are electrically compatible within the same 18V protection class and use identical DO-214AC/SMA packaging. However, they provide enhanced performance with higher clamping voltage and peak pulse current. Use these only if your circuit design can accommodate the higher transient suppression characteristics.
Q: What is the inventory status of substitute parts?
A: SMAJ18CA (MDD) has the highest inventory at 72,210 pieces. SMA6J18CA-TR (STMicroelectronics) has 10,300 pieces. SMAJ18CA-13-F (Diodes Incorporated) has 26,075 pieces. All other substitutes maintain active stock levels above 800 pieces.
Q: Does operating temperature range affect substitution?
A: SMAJ18CA (MDD) operates from -50°C to 150°C, which is slightly narrower than the original -55°C to 150°C specification. For applications requiring full -55°C operation, use SMAJ18CA-E3/5A, SMAJ18C, ATV04A180JB-HF, SM4T21CAY, or SMAJ18CA-13-F instead.
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