P4SMA91 Equivalent & Substitute Parts

Part Overview

The P4SMA91 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 77.8V reverse standoff voltage with a 131.25V maximum clamping voltage and 3.3A peak pulse current capability in a DO-214AC (SMA) package. The P4SMA91 is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	77.8	V
Voltage - Breakdown (Min)	82.18	V
Voltage - Clamping (Max) @ Ipp	131.25	V
Current - Peak Pulse (10/1000µs)	3.3	A
Power - Peak Pulse	400	W
Operating Temperature Range	-65°C ~ 150°C	TJ
Package / Case	DO-214AC, SMA	-
Type	Zener	-
Unidirectional Channels	1	-

Substitute Part Grouping Explanation

Substitution of the P4SMA91 is determined by the following critical electrical and mechanical parameters:

Voltage - Reverse Standoff (Typ): Must remain within the 77.8V specification to maintain circuit protection thresholds
Voltage - Clamping (Max) @ Ipp: Must not exceed 131.25V to ensure adequate transient suppression
Current - Peak Pulse (10/1000µs): Must support minimum 3.3A to handle expected surge conditions
Power - Peak Pulse: Must support 400W dissipation capability
Package / Case: Must be DO-214AC (SMA) for mechanical and thermal compatibility
Type: Must be Zener diode, unidirectional configuration
Operating Temperature Range: Must support -65°C to 150°C minimum

Substitute parts are grouped based on their ability to meet these parameters within acceptable engineering tolerances for the application.

Parameter Comparison

Part Number	Manufacturer	VWM (V)	Breakdown Min (V)	Clamp Max (V)	Ipp (A)	Power (W)	Temp Range (°C)	Package	Status
P4SMA91	Littelfuse Inc.	77.8	82.18	131.25	3.3	400	-65 ~ 150	DO-214AC (SMA)	Obsolete
P4SMA91A	Eaton - Electronics Division	77.8	86.5	125	3.3	400	-55 ~ 150	DO-214AC (SMA)	Active
SMAJ78A	Meritek	78	86.7	126	3.17	400	-55 ~ 150	DO-214AC (SMA)	Active
SMAJ85A	MDD	85	94.4	137	2.9	400	-50 ~ 150	DO-214AC (SMA)	Active
SMAJ90A	HY Electronic (Cayman) Limited	90	100	146	2.8	400	-55 ~ 150	DO-214AC (SMA)	Active
P4SMA100A-M3/61	Vishay General Semiconductor - Diodes Division	85.5	95	137	2.2	300	-65 ~ 150	DO-214AC (SMA)	Active
SMAJ70E3/TR13	Microchip Technology	70	77.8	125	4	500	-65 ~ 150	DO-214AC (SMA)	Active
SMAJP4KE91A-TP	Micro Commercial Co	77.8	86.5	125	3.3	400	-55 ~ 175	DO-214AC (SMA)	Active

Engineering Selection Recommendations

Primary Substitute - P4SMA91A (Eaton - Electronics Division)

The P4SMA91A is the closest electrical equivalent, maintaining the 77.8V reverse standoff voltage and 3.3A peak pulse current. The clamping voltage is reduced to 125V, which remains within acceptable suppression limits. This part is active and RoHS Compliant with unlimited moisture sensitivity rating. The operating temperature range is -55°C to 150°C, which covers most applications except those requiring the full -65°C lower limit of the original part.

Secondary Substitute - SMAJP4KE91A-TP (Micro Commercial Co)

This part matches the P4SMA91 electrical specifications identically: 77.8V standoff, 3.3A peak pulse, and 125V clamping voltage. It offers an extended upper operating temperature of 175°C and is currently active. The lower temperature limit is -55°C, consistent with P4SMA91A.

Alternative Substitutes - SMAJ78A, SMAJ85A, SMAJ90A

These parts provide higher voltage ratings (78V to 90V standoff) with comparable or slightly reduced peak pulse currents (2.8A to 3.17A). Selection depends on circuit requirements for higher voltage protection thresholds. All are active products with RoHS compliance.

Extended Range Option - P4SMA100A-M3/61 (Vishay)

This part maintains the full -65°C to 150°C operating range of the original P4SMA91. However, it features a higher 85.5V standoff voltage and reduced 2.2A peak pulse current with 300W power dissipation. Use only when the extended lower temperature range is critical and higher voltage thresholds are acceptable.

High Current Alternative - SMAJ70E3/TR13 (Microchip Technology)

This part offers the highest peak pulse current (4A) and power dissipation (500W) among available substitutes, with a lower 70V standoff voltage. It maintains the full -65°C to 150°C operating range. Select this option only when higher transient current handling is required.

Frequently Asked Questions (FAQ)

Q: Can P4SMA91A directly replace P4SMA91 in all applications?

A: P4SMA91A is electrically compatible for most applications, maintaining the same 77.8V standoff and 3.3A peak pulse specifications. The primary difference is the reduced operating temperature lower limit (-55°C vs. -65°C). Verify your application's minimum operating temperature requirement before substitution.

Q: What is the difference between clamping voltage and reverse standoff voltage?

A: Reverse standoff voltage (VWM) is the maximum voltage the diode can withstand without conducting. Clamping voltage is the maximum voltage across the diode during a transient surge at peak pulse current. Lower clamping voltage provides better transient suppression but requires higher current handling capability.

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

A: Yes, all listed substitute parts use the DO-214AC (SMA) surface-mount package, ensuring mechanical and thermal compatibility with the original P4SMA91 footprint.

Q: Which substitute offers the best compliance status?

A: P4SMA91A, SMAJ78A, SMAJ85A, SMAJ90A, P4SMA100A-M3/61, and SMAJ70E3/TR13 are all active products with RoHS3 compliance. All carry unlimited moisture sensitivity rating (MSL 1), suitable for standard manufacturing processes.

Q: Can I use SMAJ70E3/TR13 if my circuit requires higher current handling?

A: Yes, SMAJ70E3/TR13 provides 4A peak pulse current versus the original 3.3A, with 500W power dissipation capability. However, its 70V standoff voltage is lower than the P4SMA91's 77.8V, so verify that your circuit's protection threshold requirements are met.

Q: What is the impact of using a substitute with higher standoff voltage?

A: Higher standoff voltage (such as SMAJ85A at 85V or SMAJ90A at 90V) means the diode will not conduct until a higher transient voltage is reached. This may be acceptable if your circuit can tolerate higher peak voltages, but verify compatibility with downstream component ratings.

Q: Are there temperature range considerations for substitute selection?

A: Yes. The original P4SMA91 operates from -65°C to 150°C. Most active substitutes operate from -55°C to 150°C. If your application requires operation below -55°C, select P4SMA100A-M3/61 or SMAJ70E3/TR13, which maintain the -65°C lower limit.

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