SMAJ70 Equivalent & Substitute Parts Reference

Part Overview

The SMAJ70 is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. Specified with a 70V reverse standoff voltage, 118.65V maximum clamping voltage, and 4.6A peak pulse current, the SMAJ70 operates across -65°C to 150°C and is housed in a DO-214AC (SMA) package. The part is currently listed as obsolete, necessitating identification of functionally equivalent active alternatives that maintain electrical and mechanical compatibility for new designs and production continuity.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	70	V
Voltage - Breakdown (Min)	73.71	V
Voltage - Clamping (Max) @ Ipp	118.65	V
Current - Peak Pulse (10/1000µs)	4.6	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 eligibility for the SMAJ70 is determined by strict alignment across the following electrical and mechanical parameters:

Primary Substitution Criteria:

Voltage - Reverse Standoff: 70V (required)
Package / Case: DO-214AC, SMA (required for mechanical compatibility)
Type: Zener, unidirectional (required for functional equivalence)
RoHS Status: ROHS3 Compliant (required for regulatory compliance)

Secondary Compatibility Parameters:

Voltage - Clamping (Max) @ Ipp: 113V to 146V (acceptable range for general-purpose protection)
Current - Peak Pulse (10/1000µs): 4.6A to 27A (acceptable range; higher values provide enhanced transient handling)
Power - Peak Pulse: 400W to 600W (acceptable range)
Operating Temperature: Minimum -55°C to -65°C; Maximum 150°C to 175°C (acceptable range)

Parts meeting all primary criteria and falling within secondary parameter ranges are classified as direct substitutes. Parts with identical electrical specifications but different manufacturers or packaging variants are grouped as equivalent alternatives.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (V)	Voltage - Clamping (Max) @ Ipp (V)	Current - Peak Pulse (A)	Power - Peak Pulse (W)	Operating Temperature (°C)	Package	Product Status
SMAJ70	Littelfuse Inc.	70	118.65	4.6	400	-65 to 150	DO-214AC (SMA)	Obsolete
SMAJ70A	MDD	70	113	4.6	400	-50 to 150	DO-214AC (SMA)	Active
SZ1SMA70AT3G	Littelfuse Inc.	70	113	4.6	400	-65 to 150	DO-214AC (SMA)	Active
SMA6J70A-TR	STMicroelectronics	70	120	27 (8/20µs)	600	-55 to 175	DO-214AC (SMA)	Active
SMAJ70A-13-F	Diodes Incorporated	70	113	4.6	400	-55 to 150	DO-214AC (SMA)	Active
SMAJ70A-TP	Micro Commercial Co	70	113	4.6	400	-55 to 175	DO-214AC (SMA)	Active
SMAJ70A-TR	STMicroelectronics	70	146	16 (8/20µs)	400	-55 to 150	DO-214AC (SMA)	Active
SMAJ70AE3/TR13	Microchip Technology	70	113	4.4	500	-65 to 150	DO-214AC (SMA)	Active
SMAJ70E3/TR13	Microchip Technology	70	125	4	500	-65 to 150	DO-214AC (SMA)	Active
SMAT70A-13-F	Diodes Incorporated	70	100	4.6	400	-55 to 150	DO-214AC (SMA)	Active

Engineering Selection Recommendations

Primary Recommendation: SZ1SMA70AT3G (Littelfuse Inc.)

SZ1SMA70AT3G is the manufacturer-recommended successor to the obsolete SMAJ70. Manufactured by the original equipment supplier, it maintains identical reverse standoff voltage (70V), operating temperature range (-65°C to 150°C), and package specification (DO-214AC/SMA). Electrical parameters remain within acceptable tolerance: clamping voltage of 113V versus the original 118.65V represents a 4.8% variance. The part carries AEC-Q101 automotive qualification and ROHS3 compliance, ensuring regulatory continuity. Active product status guarantees long-term availability and supply chain stability.

Secondary Recommendations:

SMAJ70A (MDD) and SMAJ70A-13-F (Diodes Incorporated) provide cost-effective alternatives with identical electrical specifications (70V standoff, 113V clamping, 4.6A peak pulse, 400W power). Both are active products in ROHS3 compliance. SMAJ70A-13-F extends the upper operating temperature to 150°C (matching the original), while SMAJ70A operates to 150°C with a reduced lower temperature limit of -50°C.

SMAJ70A-TP (Micro Commercial Co) and SMAJ70A-TR (STMicroelectronics) offer enhanced thermal performance with upper operating temperatures of 175°C and 150°C respectively, suitable for applications requiring extended temperature margins. SMAJ70A-TP maintains 113V clamping voltage; SMAJ70A-TR provides 146V clamping with 16A peak pulse current, offering increased transient suppression capability.

For Enhanced Transient Protection:

SMA6J70A-TR (STMicroelectronics) delivers significantly higher peak pulse current (27A at 8/20µs) and power dissipation (600W) while maintaining 70V standoff voltage and DO-214AC packaging. This part is suitable for applications requiring superior transient handling beyond the original SMAJ70 specification.

For Extended Temperature Range:

SMAJ70AE3/TR13 and SMAJ70E3/TR13 (Microchip Technology) maintain the full -65°C to 150°C operating range with enhanced power ratings (500W). SMAJ70AE3/TR13 provides 113V clamping with 4.4A peak pulse; SMAJ70E3/TR13 offers 125V clamping with 4A peak pulse.

All recommended substitutes are ROHS3 compliant, MSL 1 rated, and available in active production status.

Frequently Asked Questions (FAQ)

Q: Can SMAJ70A directly replace SMAJ70 in existing designs?

A: Yes. SMAJ70A maintains the critical electrical parameters: 70V reverse standoff voltage, DO-214AC (SMA) package, and Zener diode type. The clamping voltage variance (113V versus 118.65V) falls within acceptable tolerance for general-purpose transient suppression. Verify that your circuit design does not depend on the specific 118.65V clamping threshold before substitution.

Q: What is the difference between SMAJ70A-TP and SMAJ70A-TR?

A: Both parts share identical electrical specifications (70V standoff, 113V clamping, 4.6A peak pulse, 400W power) and DO-214AC packaging. SMAJ70A-TP is supplied by Micro Commercial Co in Tape & Reel format with -55°C to 175°C operating range. SMAJ70A-TR is supplied by STMicroelectronics in Tape & Reel format with -55°C to 150°C operating range. Selection depends on supplier availability, lead time, and thermal requirements.

Q: Why does SMA6J70A-TR have higher peak pulse current (27A) than the original SMAJ70 (4.6A)?

A: SMA6J70A-TR belongs to the TRANSIL™ series, a higher-performance TVS family designed for enhanced transient suppression. The 27A peak pulse rating (measured at 8/20µs pulse width) versus the original 4.6A (measured at 10/1000µs) reflects different test conditions and superior energy absorption capability. This part is suitable for applications requiring greater transient protection margin while maintaining 70V standoff voltage and DO-214AC packaging.

Q: Is SMAT70A-13-F compatible with SMAJ70?

A: SMAT70A-13-F is mechanically compatible (DO-214AC/SMA package) and electrically compatible (70V standoff, Zener type, unidirectional). However, the clamping voltage is lower at 100V versus the original 118.65V. This represents a 15.8% reduction and may affect circuit protection performance in applications with tight clamping voltage specifications. Verify circuit tolerance before substitution.

Q: What does AEC-Q101 qualification on SZ1SMA70AT3G indicate?

A: AEC-Q101 is an automotive-grade qualification standard ensuring the component meets stringent reliability, temperature cycling, and stress testing requirements for automotive applications. If your design requires automotive-grade components, SZ1SMA70AT3G is the appropriate choice among available substitutes.

Q: Can I use SMAJ70E3/TR13 (125V clamping) instead of SMAJ70 (118.65V clamping)?

A: Yes, provided your circuit design tolerates the higher clamping voltage. SMAJ70E3/TR13 maintains 70V standoff voltage, DO-214AC packaging, and Zener type. The 125V clamping voltage is 5.3% higher than the original, offering slightly reduced transient suppression but maintaining functional compatibility for general-purpose applications. Confirm that downstream components can withstand the marginally higher clamping voltage.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts carry ROHS3 compliance certification, ensuring compatibility with environmental and regulatory requirements equivalent to the original SMAJ70.

Q: What is the significance of MSL 1 (Unlimited) rating?

A: MSL 1 indicates the component has unlimited shelf life and requires no special moisture control during storage or handling. This simplifies inventory management and reduces risk of moisture-induced failures during assembly, matching the original SMAJ70 specification.

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