5KP51-B Transient Voltage Suppressor (TVS) Equivalent & Substitute Parts

Part Overview

The 5KP51-B is a unidirectional Zener transient voltage suppressor diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection applications. This component features a 51V reverse standoff voltage, 86.52V maximum clamping voltage, and 5000W peak pulse power rating in a through-hole P600 axial package. The 5KP51-B is classified as obsolete; equivalent and substitute parts with active product status are available to maintain design continuity and ensure supply chain reliability.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	51	V
Voltage - Breakdown (Min)	53.73	V
Voltage - Clamping (Max) @ Ipp	86.52	V
Power - Peak Pulse	5000	W
Operating Temperature Range	-55 to 175	°C
Mounting Type	Through Hole	—
Package / Case	P600, Axial	—
Type	Zener	—
Unidirectional Channels	1	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution eligibility for the 5KP51-B is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Reverse Standoff (Typ): 51V
Voltage - Clamping (Max) @ Ipp: 82.4V to 91.1V (acceptable range for 51V standoff devices)
Power - Peak Pulse: 5000W (5kW) minimum
Type: Zener, Unidirectional
Operating Temperature: -55°C to 175°C
Mounting Type: Through Hole
Package / Case: P600, Axial (primary); alternative axial packages acceptable with mechanical verification

Secondary Substitution Criteria (Lower Power Rating):

Voltage - Reverse Standoff (Typ): 51V to 53V
Voltage - Clamping (Max) @ Ipp: 78.5V to 92V
Power - Peak Pulse: 1500W minimum (for reduced-power applications)
Type: Zener, Unidirectional
Operating Temperature: -55°C to 175°C
Mounting Type: Through Hole
Package / Case: Axial (various formats)

Substitute parts are grouped into two categories: direct equivalents maintaining 5000W power rating and P600 package compatibility, and functional alternatives with reduced power ratings or alternative axial packages suitable for lower-stress applications.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (V)	Voltage - Clamping (Max) @ Ipp (V)	Power - Peak Pulse (W)	Package / Case	Product Status	RoHS Status
5KP51-B	Littelfuse Inc.	51	86.52	5000	P600, Axial	Obsolete	ROHS3 Compliant
5KP51A	Littelfuse	51	82.4	5000	P600, Axial	Active	ROHS3 Compliant
5KP51A-B	Littelfuse Inc.	51	82.4	5000	P600, Axial	Active	ROHS3 Compliant
5KP51E3/TR13	Microchip Technology	51	91.1	5000	P600, Axial	Active	ROHS3 Compliant
5KP51A-TP	Micro Commercial Co	51	82.4	5000	R-6, Axial	Active	ROHS3 Compliant
1N5612	Microchip Technology	49	78.5	1500	G, Axial	Active	REACH Unaffected
1.5KE62A	Taiwan Semiconductor Corporation	53	85	1500	DO-201AA, Axial	Active	ROHS3 Compliant
P4KE62A-TP	Micro Commercial Co	53	85	400	DO-41, Axial	Active	REACH Unaffected
P6KE62A	Diotec Semiconductor	53	85	600	DO-15, Axial	Active	Vendor Undefined
P6KE68A	Fairchild Semiconductor	58.1	92	600	DO-15, Axial	Active	EAR99

Engineering Selection Recommendations

Tier 1 - Direct Equivalents (Recommended Primary Substitutes):

5KP51A, 5KP51A-B, and 5KP51E3/TR13 are the preferred substitutes for the obsolete 5KP51-B. All three maintain the 51V reverse standoff voltage, 5000W peak pulse power rating, and through-hole axial mounting configuration. 5KP51A and 5KP51A-B are manufactured by Littelfuse Inc., ensuring design continuity with the original part. 5KP51E3/TR13 (Microchip Technology) provides equivalent electrical performance with slightly higher clamping voltage (91.1V vs. 86.52V). All three are ROHS3 compliant and carry active product status with established supply availability.

Tier 2 - Package-Compatible Alternatives (Secondary Substitutes):

5KP51A-TP (Micro Commercial Co) maintains electrical equivalence (51V standoff, 5000W power) but uses an R-6 axial package instead of P600. This substitute is suitable when mechanical footprint flexibility exists. ROHS3 compliance and active status confirm regulatory and supply continuity.

Tier 3 - Reduced Power Rating Alternatives (Application-Dependent):

1N5612 (Microchip Technology), 1.5KE62A (Taiwan Semiconductor Corporation), P4KE62A-TP (Micro Commercial Co), and P6KE62A (Diotec Semiconductor) are functional alternatives for applications where peak pulse power requirements are lower than 5000W. These parts maintain through-hole axial mounting and general-purpose overvoltage protection capability but operate at reduced power levels (1500W, 600W, or 400W). Voltage standoff and clamping parameters remain within acceptable ranges for 51V to 53V protection circuits. Selection from this tier requires verification that application peak pulse current and energy do not exceed the specified power rating.

Compliance Considerations:

All Tier 1 and Tier 2 substitutes maintain ROHS3 compliance. Tier 3 alternatives vary in compliance status; verify regulatory requirements for specific applications before selection.

Frequently Asked Questions (FAQ)

Q: Can 5KP51A directly replace 5KP51-B without circuit modification?

A: Yes. 5KP51A maintains identical reverse standoff voltage (51V), equivalent clamping voltage (82.4V vs. 86.52V), and matching 5000W power rating. The P600 axial package is identical. No circuit modification is required.

Q: What is the difference between 5KP51A and 5KP51E3/TR13?

A: Both maintain 51V standoff and 5000W power rating. The primary difference is clamping voltage: 5KP51E3/TR13 clamps at 91.1V compared to 5KP51A at 82.4V. For circuits sensitive to clamping voltage, verify the application tolerance before substitution. Both are P600 axial packages.

Q: Can I use 5KP51A-TP as a substitute if my circuit board has P600 footprint?

A: 5KP51A-TP uses an R-6 axial package instead of P600. While both are through-hole axial formats, mechanical footprint differs. Verify that the R-6 package dimensions fit the available board space. Electrical performance is equivalent to 5KP51A.

Q: Are lower-power alternatives like 1.5KE62A suitable for my application?

A: 1.5KE62A is suitable only if your application peak pulse power requirement is 1500W or less. The 5KP51-B is rated for 5000W; substituting a 1500W part in a 5000W application will cause premature failure. Verify actual peak pulse current and energy requirements before selecting a lower-power alternative.

Q: What is the voltage difference between 51V standoff (5KP51 series) and 53V standoff (1.5KE62A, P6KE62A)?

A: The 2V difference represents a 3.9% increase in standoff voltage. For circuits designed for 51V protection, this difference may be acceptable depending on the protected circuit's overvoltage tolerance. Verify that the protected component can withstand the higher clamping voltage before substitution.

Q: Do all substitute parts have the same operating temperature range?

A: Most substitutes operate from -55°C to 175°C, matching the 5KP51-B. P6KE62A and P6KE68A operate from -50°C to 175°C, a 5°C reduction at the lower end. Verify that your application does not require operation below -50°C before selecting these alternatives.

Q: Is RoHS compliance maintained across all substitutes?

A: Tier 1 and Tier 2 substitutes (5KP51A, 5KP51A-B, 5KP51E3/TR13, 5KP51A-TP) are ROHS3 compliant. Tier 3 alternatives vary: 1.5KE62A is ROHS3 compliant; P6KE62A and P6KE68A have undefined or non-applicable RoHS status. Verify compliance requirements for your application before final selection.

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