SMAJ48 Equivalent & Substitute Parts

Part Overview

The SMAJ48 is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. This component features a 48V reverse standoff voltage, 81.27V maximum clamping voltage, and 5.2A peak pulse current capability in a DO-214AC (SMA) package. The part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	48	V
Voltage - Breakdown (Min)	50.49	V
Voltage - Clamping (Max) @ Ipp	81.27	V
Current - Peak Pulse (10/1000µs)	5.2	A
Power - Peak Pulse	400	W
Operating Temperature Range	-65 to 150	°C (TJ)
Package / Case	DO-214AC, SMA	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the SMAJ48 is determined by the following critical parameters:

Voltage - Reverse Standoff: Must be 48V (±tolerance as specified by manufacturer)
Package / Case: Must be DO-214AC (SMA) for mechanical and thermal compatibility
Mounting Type: Must be Surface Mount
Voltage - Clamping (Max) @ Ipp: Acceptable range 77.4V to 100V (within circuit protection requirements)
Current - Peak Pulse (10/1000µs): Minimum 5.2A; higher values acceptable
Power - Peak Pulse: Minimum 400W; higher values acceptable
Operating Temperature Range: Must support -55°C to 150°C minimum
RoHS Status: ROHS3 Compliant required

Substitute parts are grouped into two categories based on clamping voltage performance:

Group A (77.4V Clamping): SMAJ48A (MDD), SZ1SMA48AT3G (Littelfuse), SMAJ48A-13-F (Diodes), SMAJ48A-TP (Micro Commercial Co), TV04A480J-G (Comchip), SMAJ48AE3/TR13 (Microchip)

Group B (85.5V–100V Clamping): SMAJ48E3/TR13 (Microchip), SM4T56AY (STMicroelectronics), SMAJ48A-TR (STMicroelectronics)

Parameter Comparison

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
SMAJ48	Littelfuse Inc.	48	50.49	81.27	5.2	400	-65 to 150	DO-214AC (SMA)	Obsolete
SMAJ48A	MDD	48	53.3	77.4	5.2	400	-50 to 150	DO-214AC (SMA)	Active
SZ1SMA48AT3G	Littelfuse Inc.	48	53.3	77.4	5.2	400	-65 to 150	DO-214AC (SMA)	Active
SMAJ48A-13-F	Diodes Incorporated	48	53.3	77.4	5.2	400	-55 to 150	DO-214AC (SMA)	Active
SMAJ48A-TP	Micro Commercial Co	48	53.3	77.4	5.2	400	-55 to 175	DO-214AC (SMA)	Active
TV04A480J-G	Comchip Technology	48	53.3	77.4	5.17	400	-55 to 150	DO-214AC (SMA)	Active
SMAJ48AE3/TR13	Microchip Technology	48	53.3	77.4	6.5	500	-65 to 150	DO-214AC (SMA)	Active
SMAJ48E3/TR13	Microchip Technology	48	53.3	85.5	5.8	500	-65 to 150	DO-214AC (SMA)	Active
SM4T56AY	STMicroelectronics	48	53.3	100	23 (8/20µs)	400	-55 to 150	DO-214AC (SMA)	Active
SMAJ48A-TR	STMicroelectronics	48	53.3	100	23 (8/20µs)	400	-55 to 150	DO-214AC (SMA)	Active

Engineering Selection Recommendations

Primary Substitutes (Direct Replacement)

SZ1SMA48AT3G (Littelfuse Inc.) and SMAJ48AE3/TR13 (Microchip Technology) are the preferred substitutes. Both maintain the 48V reverse standoff voltage, DO-214AC package, and support the full -65°C to 150°C operating temperature range of the original SMAJ48. SZ1SMA48AT3G is manufacturer-recommended and carries AEC-Q101 automotive qualification. SMAJ48AE3/TR13 offers enhanced current handling (6.5A) and power dissipation (500W) with identical temperature range coverage.

Secondary Substitutes (Functional Equivalents)

SMAJ48A (MDD), SMAJ48A-13-F (Diodes), SMAJ48A-TP (Micro Commercial Co), and TV04A480J-G (Comchip) provide functional equivalence with 77.4V clamping voltage and 5.2A peak pulse current. All are active products with ROHS3 compliance. Temperature range varies: SMAJ48A-TP extends to 175°C (TA), while others support -55°C minimum. These are suitable for applications where the lower clamping voltage is acceptable.

Higher Performance Alternatives

SMAJ48E3/TR13 (Microchip) and SM4T56AY / SMAJ48A-TR (STMicroelectronics) provide increased clamping voltage (85.5V–100V) and higher peak pulse current (5.8A–23A). These are appropriate for circuits requiring enhanced transient suppression or where higher current events are anticipated. Both manufacturers provide AEC-Q101 automotive qualification.

Compliance Considerations

All substitute parts are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity. Littelfuse SZ1SMA48AT3G and STMicroelectronics parts carry AEC-Q101 automotive qualification, suitable for automotive and industrial applications. Selection should account for application-specific temperature requirements and transient event severity.

Frequently Asked Questions (FAQ)

Q: Can SMAJ48A (77.4V clamping) replace SMAJ48 (81.27V clamping) directly?

A: Yes, within circuit design margins. The 77.4V clamping voltage is lower than the original 81.27V, providing tighter voltage suppression. This is acceptable if the circuit design accommodates the reduced clamping threshold. Verify that downstream components tolerate the lower peak voltage.

Q: What is the difference between Group A (77.4V) and Group B (85.5V–100V) substitutes?

A: Group A substitutes clamp at 77.4V, providing tighter overvoltage suppression. Group B substitutes clamp at 85.5V–100V, closer to the original SMAJ48 performance (81.27V). Group B is preferred if the original clamping voltage specification is critical to circuit protection. Group A is acceptable for applications with design margin.

Q: Are all substitutes available in the same DO-214AC (SMA) package?

A: Yes. All listed substitutes use the DO-214AC (SMA) surface-mount package, ensuring mechanical and thermal compatibility with the original SMAJ48 footprint.

Q: Which substitute offers the best temperature range coverage?

A: SMAJ48A-TP (Micro Commercial Co) extends to 175°C (TA), the widest range among substitutes. SZ1SMA48AT3G, SMAJ48AE3/TR13, and SMAJ48E3/TR13 all support -65°C to 150°C (TJ), matching the original SMAJ48 specification.

Q: Do any substitutes carry automotive qualification?

A: Yes. SZ1SMA48AT3G (Littelfuse), SM4T56AY (STMicroelectronics), and SMAJ48A-TR (STMicroelectronics) carry AEC-Q101 automotive qualification, suitable for automotive and harsh-environment applications.

Q: What is the difference between SMAJ48AE3/TR13 and SMAJ48E3/TR13?

A: Both are Microchip products with identical temperature range (-65°C to 150°C). SMAJ48AE3/TR13 clamps at 77.4V with 6.5A peak pulse current and 500W power dissipation. SMAJ48E3/TR13 clamps at 85.5V with 5.8A peak pulse current and 500W power dissipation. Select based on required clamping voltage.

Q: Can STMicroelectronics SM4T56AY or SMAJ48A-TR (100V clamping, 23A current) be used as drop-in replacements?

A: These parts are functionally compatible but represent a performance upgrade. The 100V clamping voltage is higher than the original 81.27V, and the 23A peak pulse current significantly exceeds the 5.2A specification. Use only if the circuit design accommodates higher clamping voltage and the increased current capability does not introduce unintended circuit behavior.

Q: Are all substitutes ROHS3 compliant?

A: Yes. All listed substitute parts are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity level, meeting environmental and regulatory requirements equivalent to the original SMAJ48.

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