SMAJ28C Equivalent & Substitute Parts

Part Overview

The SMAJ28C is a transient voltage suppressor (TVS) diode manufactured by Littelfuse, designed for general-purpose overvoltage protection in surface-mount applications. This component features a 28V reverse standoff voltage, 47.67V maximum clamping voltage, and 8.8A peak pulse current in a DO-214AC (SMA) package. The SMAJ28C is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Reverse Standoff Voltage (Typ)	28V
Breakdown Voltage (Min)	29.48V
Clamping Voltage (Max) @ Ipp	47.67V
Peak Pulse Current (10/1000µs)	8.8A
Peak Pulse Power	400W
Package Type	DO-214AC (SMA)
Operating Temperature Range	-65°C to 150°C (TJ)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the SMAJ28C is determined by the following critical parameters:

Reverse standoff voltage of 28V (±tolerance)
Breakdown voltage minimum of 29.48V to 31.1V
Package compatibility: DO-214AC (SMA) surface mount
Peak pulse current capability: minimum 8.8A
Peak pulse power: minimum 400W
RoHS3 compliance and MSL 1 rating

Substitute parts are grouped into two categories based on electrical performance:

Category A (Direct Electrical Equivalents): Parts with clamping voltages between 45.4V and 47.67V and peak pulse current of 8.8A to 11A. These provide equivalent protection characteristics with minimal circuit impact.

Category B (Enhanced Performance Substitutes): Parts with higher peak pulse current (13.2A to 68A) and increased power dissipation (500W to 600W). These offer superior transient suppression capability while maintaining the same standoff voltage and package footprint.

Parameter Comparison

Part Number	Manufacturer	Standoff Voltage	Breakdown Voltage (Min)	Clamping Voltage (Max)	Peak Pulse Current	Peak Pulse Power	Operating Temperature	Product Status
SMAJ28C	Littelfuse	28V	29.48V	47.67V	8.8A	400W	-65°C to 150°C	Obsolete
SMAJ28CA	MDD	28V	31.1V	45.4V	8.8A	400W	-50°C to 150°C	Active
SZ1SMA28CAT3G	Littelfuse Inc.	28V	31.1V	45.4V	8.8A	400W	-65°C to 150°C	Active
SMA6J28CA-TP	Micro Commercial Co	28V	31.1V	45.4V	13.2A	600W	-55°C to 175°C	Active
SMA6J28CA-TR	STMicroelectronics	28V	31.1V	51.6V	68A (8/20µs)	600W	-55°C to 175°C	Active
SMAJ28CA-13-F	Diodes Incorporated	28V	31.1V	45.4V	8.8A	400W	-55°C to 150°C	Active
SMAJ28CA-TP	Micro Commercial Co	28V	31.1V	45.4V	8.8A	400W	-55°C to 175°C	Active
SMAJ28CA-TR	STMicroelectronics	28V	31.1V	59V	39A (8/20µs)	400W	-55°C to 150°C	Active
SMAJ28CAE3/TR13	Microchip Technology	28V	31.1V	45.4V	11A	500W	-65°C to 150°C	Active
SMAJ28CE3/TR13	Microchip Technology	28V	31.1V	50V	9.9A	500W	-65°C to 150°C	Active

Engineering Selection Recommendations

All substitute parts listed are active products with ROHS3 compliance and MSL 1 rating, ensuring regulatory compliance and moisture resistance equivalent to the original SMAJ28C.

For applications requiring direct electrical equivalence with minimal circuit redesign, select from Category A substitutes: SMAJ28CA (MDD), SZ1SMA28CAT3G (Littelfuse), SMAJ28CA-13-F (Diodes Incorporated), SMAJ28CA-TP (Micro Commercial Co), or SMAJ28CAE3/TR13 (Microchip Technology). These maintain the 8.8A to 11A peak pulse current range and 400W to 500W power dissipation.

For applications requiring enhanced transient suppression capability, Category B substitutes SMA6J28CA-TP (Micro Commercial Co) and SMA6J28CA-TR (STMicroelectronics) provide 13.2A to 68A peak pulse current with 600W power dissipation, enabling protection against more severe transient events while maintaining the same 28V standoff voltage and DO-214AC package footprint.

Temperature range considerations: SZ1SMA28CAT3G and SMAJ28CAE3/TR13 maintain the original -65°C lower operating limit. SMA6J28CA-TP and SMA6J28CA-TR extend the upper temperature limit to 175°C, suitable for high-temperature applications.

Frequently Asked Questions (FAQ)

Q: Can I use any substitute part directly without circuit modification?

A: Yes, all listed substitutes maintain the 28V standoff voltage and DO-214AC package compatibility. However, verify that your circuit can accommodate the clamping voltage range (45.4V to 59V) and peak pulse current specifications of the selected substitute.

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

A: Category A substitutes (8.8A to 11A, 400W to 500W) provide equivalent protection to the original SMAJ28C. Category B substitutes (13.2A to 68A, 600W) offer enhanced transient suppression for circuits exposed to more severe overvoltage events. Category B parts are backward compatible but provide additional margin.

Q: Are all substitutes available in the same packaging options?

A: All substitutes use the DO-214AC (SMA) surface-mount package. Packaging formats (Tape & Reel, Bulk, Cut Tape) vary by manufacturer and part number. Verify packaging availability with your supplier for production requirements.

Q: Which substitute has the widest operating temperature range?

A: SMA6J28CA-TP and SMA6J28CA-TR both support -55°C to 175°C, extending the upper temperature limit by 25°C compared to the original SMAJ28C (-65°C to 150°C).

Q: Is the higher clamping voltage of some substitutes a concern?

A: Clamping voltage variations (45.4V to 59V) are within acceptable ranges for 28V standoff TVS diodes. Higher clamping voltages provide additional protection margin. Verify compatibility with downstream components rated for the maximum clamping voltage of your selected substitute.

Q: Are all substitutes RoHS3 compliant?

A: Yes, all listed substitutes are ROHS3 compliant with MSL 1 rating, meeting current environmental and reliability standards.

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