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SMAJ20 Transient Voltage Suppressor Diode Equivalent & Substitute Parts
Part Overview
The SMAJ20 is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. The device features a 20V reverse standoff voltage with a 34.02V maximum clamping voltage at peak pulse current of 12.3A, packaged in the DO-214AC (SMA) form factor. The SMAJ20 is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.
Substiute Parts
Key Parameters
| Parameter | Value | Unit |
|---|---|---|
| Voltage - Reverse Standoff (Typ) | 20 | V |
| Voltage - Breakdown (Min) | 21.02 | V |
| Voltage - Clamping (Max) @ Ipp | 34.02 | V |
| Current - Peak Pulse (10/1000µs) | 12.3 | A |
| Power - Peak Pulse | 400 | W |
| Operating Temperature Range | -65 to 150 | °C (TJ) |
| Package / Case | DO-214AC, SMA | — |
| Type | Zener | — |
| Unidirectional Channels | 1 | — |
| RoHS Status | ROHS3 Compliant | — |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) | — |
Substitute Part Grouping Explanation
Substitution of the SMAJ20 is determined by strict adherence to the following electrical and mechanical parameters:
Primary Substitution Criteria:
- Voltage - Reverse Standoff (Typ): 20V
- Voltage - Breakdown (Min): 21.02V to 22.2V range
- Package / Case: DO-214AC (SMA)
- Type: Zener, Unidirectional
- Mounting Type: Surface Mount
- RoHS Status: ROHS3 Compliant
- Moisture Sensitivity Level: 1 (Unlimited)
Secondary Compatibility Parameters:
- Voltage - Clamping (Max) @ Ipp: 32.4V to 42.8V (acceptable range for general-purpose protection)
- Current - Peak Pulse: 12.3A to 93A (dependent on application requirements)
- Power - Peak Pulse: 400W to 4000W (dependent on application requirements)
- Operating Temperature Range: -65°C to 150°C minimum coverage
Substitute parts are grouped into two categories based on peak pulse current and clamping voltage characteristics: standard current devices (12.3A to 15.4A) and high-current devices (54A to 93A). Selection depends on the specific transient energy absorption requirements of the application.
Parameter Comparison
| Manufacturer Part Number | Manufacturer | Voltage - Reverse Standoff (V) | Voltage - Breakdown Min (V) | Voltage - Clamping Max @ Ipp (V) | Current - Peak Pulse (A) | Power - Peak Pulse (W) | Operating Temp (°C) | Package | Product Status |
|---|---|---|---|---|---|---|---|---|---|
| SMAJ20 | Littelfuse Inc. | 20 | 21.02 | 34.02 | 12.3 | 400 | -65 to 150 | DO-214AC (SMA) | Obsolete |
| SMAJ20A | MDD | 20 | 22.2 | 32.4 | 12.3 | 400 | -50 to 150 | DO-214AC (SMA) | Active |
| SMAJ20A-13-F | Diodes Incorporated | 20 | 22.2 | 32.4 | 12.3 | 400 | -55 to 150 | DO-214AC (SMA) | Active |
| SMAJ20A-TP | Micro Commercial Co | 20 | 22.2 | 32.4 | 12.3 | 400 | -55 to 175 | DO-214AC (SMA) | Active |
| SMAJ20AE3/TR13 | Microchip Technology | 20 | 22.2 | 32.4 | 15.4 | 500 | -65 to 150 | DO-214AC (SMA) | Active |
| SMAJ20A-TR | STMicroelectronics | 20 | 22.2 | 42.8 | 54 (8/20µs) | 400 | -55 to 150 | DO-214AC (SMA) | Active |
| SMA6J20A-E3/5A | Vishay General Semiconductor | 20 | 22.2 | 36.8 | 93 (8/20µs) | 4000 | -55 to 150 | DO-214AC (SMA) | Active |
| SMA6J20A-E3/61 | Vishay General Semiconductor | 20 | 22.2 | 36.8 | 93 (8/20µs) | 4000 | -55 to 150 | DO-214AC (SMA) | Active |
| SM4T23AY | STMicroelectronics | 20 | 22.2 | 42.8 | 54 (8/20µs) | 400 | -55 to 150 | DO-214AC (SMA) | Active |
| SZ1SMA20AT3G | onsemi | 20 | — | — | — | — | — | DO-214AC (SMA) | Active |
Engineering Selection Recommendations
Standard Current Substitutes (12.3A to 15.4A Peak Pulse):
SMAJ20A (MDD), SMAJ20A-13-F (Diodes Incorporated), SMAJ20A-TP (Micro Commercial Co), and SMAJ20AE3/TR13 (Microchip Technology) are direct functional equivalents with active product status. All maintain the 20V reverse standoff voltage and DO-214AC package specification. SMAJ20A-TP offers the widest operating temperature range (-55°C to 175°C), suitable for extended temperature applications. SMAJ20AE3/TR13 provides increased peak pulse current (15.4A) and power dissipation (500W) within the standard current category.
High-Current Substitutes (54A to 93A Peak Pulse):
SMAJ20A-TR (STMicroelectronics), SM4T23AY (STMicroelectronics), SMA6J20A-E3/5A, and SMA6J20A-E3/61 (Vishay General Semiconductor) are suitable for applications requiring higher transient energy absorption. These devices maintain the 20V reverse standoff voltage and DO-214AC package but feature significantly higher peak pulse current ratings and clamping voltages. SMA6J20A variants provide the highest power dissipation (4000W) and peak pulse current (93A). SM4T23AY and SMAJ20A-TR are qualified to AEC-Q101 automotive standards where applicable.
All substitute parts are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating, matching the original SMAJ20 specification.
Frequently Asked Questions (FAQ)
Q: Can I use a substitute part with higher peak pulse current than the original SMAJ20?
A: Yes. Higher peak pulse current ratings (54A or 93A variants) are compatible substitutes provided the 20V reverse standoff voltage, DO-214AC package, and ROHS3 compliance are maintained. Higher current ratings provide additional transient energy absorption capability without compromising circuit protection function.
Q: What is the difference between the standard current (12.3A) and high-current (54A to 93A) substitute options?
A: Standard current substitutes (SMAJ20A, SMAJ20A-13-F, SMAJ20A-TP, SMAJ20AE3/TR13) are direct replacements for the original SMAJ20 with equivalent peak pulse current. High-current substitutes (SMAJ20A-TR, SM4T23AY, SMA6J20A series) provide higher transient energy absorption and are suitable for applications with greater overvoltage stress requirements. Selection depends on the specific transient energy levels in the application circuit.
Q: Are all substitute parts available in the same packaging as the original SMAJ20?
A: Yes. All listed substitute parts use the DO-214AC (SMA) surface-mount package, ensuring mechanical and electrical compatibility with the original SMAJ20 footprint and PCB layout.
Q: Does the clamping voltage variation among substitutes affect compatibility?
A: Clamping voltage variations (32.4V to 42.8V) are within acceptable ranges for general-purpose transient voltage suppression at the 20V standoff level. Selection should be based on the specific overvoltage protection threshold required by the application circuit. Lower clamping voltages (32.4V) provide tighter protection margins, while higher clamping voltages (42.8V) allow greater transient voltage excursions.
Q: Which substitute part offers the widest operating temperature range?
A: SMAJ20A-TP (Micro Commercial Co) offers the widest operating temperature range of -55°C to 175°C, compared to the original SMAJ20 specification of -65°C to 150°C. This extended upper temperature limit is suitable for high-temperature applications.
Q: Are automotive-qualified substitutes available?
A: Yes. SM4T23AY (STMicroelectronics) is qualified to AEC-Q101 automotive standards and carries automotive-grade designation, suitable for automotive and industrial applications requiring automotive component qualification.
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