P6SMB39 Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The P6SMB39 is a unidirectional Zener transient voltage suppressor diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection applications. This surface-mount component operates in the DO-214AA (SMB) package with a reverse standoff voltage of 33.3V and peak pulse power rating of 600W. The part is currently classified as obsolete, necessitating identification of active equivalent and substitute components that maintain electrical and mechanical compatibility for new designs and production continuity.

Key Parameters

Parameter	Value	Unit
Reverse Standoff Voltage (Typ)	33.3	V
Voltage - Breakdown (Min)	35.15	V
Voltage - Clamping (Max) @ Ipp	56.6	V
Current - Peak Pulse (10/1000µs)	11.3	A
Power - Peak Pulse	600	W
Operating Temperature Range	-55 to 150	°C (TJ)
Package / Case	DO-214AA, SMB	—
Mounting Type	Surface Mount	—
Type	Zener	—
Unidirectional Channels	1	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the P6SMB39 is determined by strict adherence to the following electrical and mechanical parameters:

Critical Substitution Parameters:

Reverse Standoff Voltage (Typ): 33.3V
Package / Case: DO-214AA, SMB (surface mount)
Mounting Type: Surface Mount
Type: Zener, Unidirectional (1 channel)
Power - Peak Pulse: 600W
Moisture Sensitivity Level: 1 (Unlimited)

Acceptable Variation Range:

Voltage - Clamping (Max) @ Ipp: 53.9V to 69.7V (within design tolerance for overvoltage protection)
Current - Peak Pulse (10/1000µs): 11.1A to 57A (dependent on clamping voltage and application requirements)
Operating Temperature Range: -55°C to 175°C (extended range acceptable)

All substitute parts listed maintain the same reverse standoff voltage (33.3V), package format (DO-214AA/SMB), and core Zener diode functionality. Variations in clamping voltage and peak pulse current reflect different manufacturer implementations within the P6SMB series and related product lines, all suitable for general-purpose transient voltage suppression applications.

Parameter Comparison

Part Number	Manufacturer	Reverse Standoff (V)	Clamping (V) @ Ipp	Peak Pulse Current (A)	Temp Range (°C)	Package	Status
P6SMB39	Littelfuse Inc.	33.3	56.6	11.3	-55 to 150	DO-214AA, SMB	Obsolete
P6SMB39A	Eaton - Electronics Division	33.3	53.9	11.3	-55 to 150	DO-214AA, SMB	Active
SZP6SMB39AT3G	Littelfuse	33.3	53.9	11.2	-65 to 150	DO-214AA, SMB	Active
P6SMB39A-M3/52	Vishay General Semiconductor - Diodes Division	33.3	53.9	11.1	-65 to 150	DO-214AA, SMB	Active
P6SMB39A-M3/5B	Vishay General Semiconductor - Diodes Division	33.3	53.9	11.1	-65 to 150	DO-214AA, SMB	Active
SM6T39A	STMicroelectronics	33.3	69.7	57	-55 to 150	DO-214AA, SMB	Active
SM6T39A-E3/52	Vishay General Semiconductor - Diodes Division	33.3	53.9	11.1	-65 to 150	DO-214AA, SMB	Active
SM6T39A-E3/5B	Vishay General Semiconductor - Diodes Division	33.3	53.9	11.1	-65 to 150	DO-214AA, SMB	Active
SM6T39AY	STMicroelectronics	33.3	69.7	57	-55 to 150	DO-214AA, SMB	Active
SMBJP6KE39A-TP	Micro Commercial Co	33.3	53.9	11.3	-55 to 175	DO-214AA, SMB	Active

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility): P6SMB39A (Eaton), P6SMB39A-M3/52 (Vishay), and SMBJP6KE39A-TP (Micro Commercial Co) provide direct electrical equivalence with clamping voltages of 53.9V and peak pulse currents of 11.1A to 11.3A. All three are active products with ROHS3 compliance and unlimited moisture sensitivity rating. These parts are suitable for direct replacement in existing designs without circuit modification.

Secondary Substitutes (Extended Temperature Range): SZP6SMB39AT3G (Littelfuse), P6SMB39A-M3/5B (Vishay), SM6T39A-E3/52 (Vishay), and SM6T39A-E3/5B (Vishay) extend the lower operating temperature limit to -65°C while maintaining the same electrical characteristics. These components are appropriate for applications requiring enhanced low-temperature performance. All maintain ROHS3 compliance and unlimited MSL rating.

Alternative Substitutes (Higher Peak Pulse Current): SM6T39A (STMicroelectronics) and SM6T39AY (STMicroelectronics) feature significantly higher peak pulse current (57A at 8/20µs) and clamping voltage (69.7V). These parts are suitable for applications requiring enhanced transient suppression capability. SM6T39AY includes automotive-grade qualification (AEC-Q101), making it appropriate for automotive and harsh-environment applications.

Compliance Considerations: All substitute parts maintain ROHS3 compliance and MSL Level 1 (Unlimited) rating, ensuring compatibility with modern manufacturing processes and storage requirements. Selection should be based on specific application requirements for operating temperature range, peak pulse current capacity, and clamping voltage tolerance.

Frequently Asked Questions (FAQ)

Q: Can P6SMB39A directly replace P6SMB39 in existing designs? A: Yes. P6SMB39A maintains the same reverse standoff voltage (33.3V), package format (DO-214AA/SMB), and core Zener functionality. The clamping voltage is slightly lower (53.9V vs. 56.6V), which is within acceptable tolerance for general-purpose overvoltage protection. No circuit modifications are required.

Q: What is the difference between clamping voltage variations (53.9V vs. 56.6V vs. 69.7V)? A: Clamping voltage represents the maximum voltage across the diode during transient suppression at peak pulse current. Lower clamping voltages (53.9V) provide tighter voltage regulation, while higher clamping voltages (69.7V) allow greater voltage excursion. Selection depends on the protected circuit's voltage tolerance. All values within the listed range are acceptable substitutes for the P6SMB39.

Q: Are all substitute parts available in the same package? A: Yes. All listed substitute parts use the DO-214AA (SMB) surface-mount package, ensuring mechanical and footprint compatibility. Packaging formats (Cut Tape, Tape & Reel, Tape & Box) differ by supplier but do not affect component functionality or PCB mounting.

Q: Why do some substitutes have higher peak pulse current ratings (57A vs. 11.3A)? A: Peak pulse current capacity depends on the diode's internal design and thermal characteristics. Higher ratings (SM6T39A, SM6T39AY at 57A) indicate enhanced transient suppression capability suitable for high-energy transient events. Lower ratings (11.1A to 11.3A) are sufficient for general-purpose applications. Selection should match the application's transient energy requirements.

Q: What is the significance of AEC-Q101 qualification on SM6T39AY? A: AEC-Q101 is an automotive industry qualification standard ensuring component reliability under automotive operating conditions. SM6T39AY is suitable for automotive and mission-critical applications requiring enhanced reliability documentation. Non-automotive applications can use any listed substitute.

Q: Can I use SM6T39AY (automotive-grade) in non-automotive applications? A: Yes. Automotive-grade components meet or exceed general-purpose specifications and are fully compatible with non-automotive applications. Using automotive-grade components in non-automotive designs provides additional reliability margin without adverse effects.

Q: Are all substitutes RoHS3 compliant? A: Yes. All listed substitute parts are ROHS3 compliant, meeting current environmental and hazardous substance restrictions. This ensures compatibility with modern manufacturing and regulatory requirements.

Q: What is MSL Level 1 (Unlimited)? A: Moisture Sensitivity Level 1 (Unlimited) indicates the component has no moisture sensitivity restrictions. These parts can be stored indefinitely without special humidity control and do not require baking before soldering, simplifying supply chain and manufacturing processes.

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