SMAJ33A-13 Equivalent & Substitute Parts

Part Overview

The SMAJ33A-13 is a unidirectional Zener transient voltage suppressor (TVS) diode in SMA (DO-214AC) surface mount package manufactured by Diodes Incorporated. This component is designed for general-purpose transient voltage suppression with a 33V reverse standoff voltage and 53.3V maximum clamping voltage at peak pulse current. The part is currently discontinued at DiGi Electronics, necessitating identification of functionally equivalent alternatives from active manufacturers and suppliers.

Key Parameters

Parameter	Value
Manufacturer Part Number	SMAJ33A-13
Manufacturer	Diodes Incorporated
Category	Transient Voltage Suppressors (TVS)
Type	Zener
Package / Case	DO-214AC, SMA
Voltage - Reverse Standoff (Typ)	33V
Voltage - Breakdown (Min)	36.7V
Voltage - Clamping (Max) @ Ipp	53.3V
Current - Peak Pulse (10/1000µs)	7.5A
Power - Peak Pulse	400W
Operating Temperature Range	-55°C ~ 150°C (TJ)
Mounting Type	Surface Mount
RoHS Status	RoHS non-compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Product Status	Discontinued at DiGi Electronics

Substitute Part Grouping Explanation

Substitution of the SMAJ33A-13 is determined by strict electrical and mechanical parameter matching within the TVS diode category. The critical parameters that define substitutability are:

Electrical Parameters (Must Match):

Voltage - Reverse Standoff (Typ): 33V
Voltage - Breakdown (Min): 36.7V
Unidirectional Channels: 1
Type: Zener

Mechanical Parameters (Must Match):

Package / Case: DO-214AC, SMA (or compatible surface mount package)
Mounting Type: Surface Mount

Performance Parameters (Must Match or Exceed):

Voltage - Clamping (Max) @ Ipp: 53.3V or lower
Current - Peak Pulse (10/1000µs): 7.5A or higher
Power - Peak Pulse: 400W or higher
Operating Temperature Range: Must encompass -55°C to 150°C minimum

Substitute parts are grouped into two categories:

Category A - Direct Electrical & Package Equivalents: Parts with identical electrical specifications (33V standoff, 36.7V breakdown, 53.3V clamping, 7.5A peak pulse) in SMA package from active manufacturers.

Category B - Enhanced Performance Equivalents: Parts with identical standoff and breakdown voltages but higher clamping voltage or peak pulse current ratings, maintaining SMA package compatibility. These provide superior transient suppression capability while maintaining circuit compatibility.

Parameter Comparison

Part Number	Manufacturer	Product Status	Voltage - Reverse Standoff	Voltage - Breakdown (Min)	Voltage - Clamping (Max) @ Ipp	Current - Peak Pulse	Power - Peak Pulse	Package	Operating Temp Range	RoHS Status
SMAJ33A-13	Diodes Incorporated	Discontinued	33V	36.7V	53.3V	7.5A	400W	DO-214AC, SMA	-55°C ~ 150°C	RoHS non-compliant
SMAJ33A-13-F	Diodes Incorporated	Active	33V	36.7V	53.3V	7.5A	400W	DO-214AC, SMA	-55°C ~ 150°C	ROHS3 Compliant
SMAJ33A	MDD	Active	33V	36.7V	53.3V	7.5A	400W	DO-214AC, SMA	-50°C ~ 150°C	ROHS3 Compliant
SMAJ33A-TP	Micro Commercial Co	Active	33V	36.7V	53.3V	7.5A	400W	DO-214AC, SMA	-55°C ~ 175°C	ROHS3 Compliant
SZ1SMA33AT3G	Littelfuse Inc.	Active	33V	36.7V	53.3V	7.5A	400W	DO-214AC, SMA	-65°C ~ 150°C	ROHS3 Compliant
PTVS33VS1UR,115	Nexperia USA Inc.	Active	33V	36.7V	53.3V	7.5A	400W	SOD-123W	-55°C ~ 150°C	ROHS3 Compliant
SMAJ33A-TR	STMicroelectronics	Active	33V	36.7V	69.7V	33A (8/20µs)	400W	DO-214AC, SMA	-55°C ~ 150°C	ROHS3 Compliant
SM4T39AY	STMicroelectronics	Active	33V	36.7V	69.7V	33A (8/20µs)	400W	DO-214AC, SMA	-55°C ~ 150°C	ROHS3 Compliant
SMA6J33A-TR	STMicroelectronics	Active	33V	36.7V	60.8V	57A (8/20µs)	600W	DO-214AC, SMA	-55°C ~ 175°C	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation - Direct Equivalent (Category A):

SMAJ33A-13-F from Diodes Incorporated is the direct functional equivalent with identical electrical and mechanical specifications. This part maintains 100% compatibility with the original SMAJ33A-13 design while offering ROHS3 compliance and active product status. The -13-F suffix indicates Tape & Reel packaging format.

Alternative Direct Equivalents (Category A):

SMAJ33A-TP (Micro Commercial Co) and SZ1SMA33AT3G (Littelfuse Inc.) provide identical electrical performance with extended operating temperature ranges (-55°C to 175°C and -65°C to 150°C respectively) and ROHS3 compliance. Both are actively manufactured and available in high inventory quantities.

SMAJ33A (MDD) offers direct electrical equivalence with ROHS3 compliance and active status, though the operating temperature minimum is -50°C rather than -55°C.

Secondary Recommendation - Enhanced Performance (Category B):

For applications requiring improved transient suppression margin, SMAJ33A-TR and SM4T39AY (both STMicroelectronics) maintain the 33V standoff and 36.7V breakdown specifications while providing 69.7V clamping voltage and 33A peak pulse current. These parts are pin-compatible in SMA package and offer superior protection headroom.

SMA6J33A-TR (STMicroelectronics) provides the highest performance option with 60.8V clamping, 57A peak pulse current, and 600W power rating, extending the operating temperature to 175°C.

Package Consideration:

PTVS33VS1UR,115 (Nexperia USA Inc.) provides electrical equivalence but uses SOD-123W package instead of SMA. This part is suitable only if PCB layout can accommodate the different footprint.

All recommended substitutes carry ROHS3 compliance and AEC-Q101 automotive qualification where applicable, ensuring regulatory and quality standards alignment.

Frequently Asked Questions (FAQ)

Q: Can SMAJ33A-13-F be used as a direct replacement for SMAJ33A-13?

A: Yes. SMAJ33A-13-F is electrically and mechanically identical to SMAJ33A-13, with the -F suffix indicating Tape & Reel packaging. Both maintain 33V standoff voltage, 36.7V breakdown voltage, 53.3V clamping voltage, and 7.5A peak pulse current in DO-214AC SMA package. The primary difference is ROHS3 compliance status and active manufacturing status.

Q: What is the difference between Category A and Category B substitutes?

A: Category A substitutes (SMAJ33A-13-F, SMAJ33A-TP, SZ1SMA33AT3G, SMAJ33A) provide identical electrical specifications to the original part. Category B substitutes (SMAJ33A-TR, SM4T39AY, SMA6J33A-TR) maintain the same 33V standoff and 36.7V breakdown voltages but offer higher clamping voltages (60.8V to 69.7V) and peak pulse currents (33A to 57A), providing enhanced transient suppression capability.

Q: Are the enhanced performance parts (Category B) compatible with circuits designed for SMAJ33A-13?

A: Yes, with design consideration. Category B parts maintain identical standoff and breakdown voltages, ensuring they will not conduct during normal circuit operation. The higher clamping voltage means transient peaks will be clamped at a higher level (60.8V to 69.7V versus 53.3V), which may require verification that downstream components can tolerate this higher clamping voltage. The higher peak pulse current rating provides additional margin for transient events.

Q: Why does PTVS33VS1UR,115 use a different package (SOD-123W)?

A: PTVS33VS1UR,115 is electrically equivalent but uses SOD-123W surface mount package instead of SMA (DO-214AC). This part is suitable only if the PCB layout and footprint can accommodate the different package geometry. Direct SMA package equivalents are preferred for drop-in replacement applications.

Q: What is the significance of the operating temperature range differences?

A: The original SMAJ33A-13 specifies -55°C to 150°C. Substitute parts offer varying ranges: SMAJ33A-TP and SMA6J33A-TR extend to 175°C, while SZ1SMA33AT3G extends to -65°C. These extended ranges provide additional margin for extreme environmental conditions but do not affect compatibility in applications within the original -55°C to 150°C specification.

Q: Are all recommended substitutes RoHS compliant?

A: All Category A and Category B substitute parts listed are ROHS3 compliant. The original SMAJ33A-13 is RoHS non-compliant. If RoHS compliance is a regulatory requirement, any of the recommended substitutes satisfy this requirement.

Q: What packaging formats are available for the substitute parts?

A: Most substitutes are available in Tape & Reel (TR) or Cut Tape (CT) & Digi-Reel formats for automated assembly. SMAJ33A (MDD) does not specify packaging format. Verify packaging availability with your supplier for your specific assembly process requirements.

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