TZX18C-TAP Equivalent & Substitute Parts

Part Overview

The TZX18C-TAP is an 18 V, 500 mW Zener diode manufactured by Vishay General Semiconductor - Diodes Division in a through-hole DO-35 (DO-204AH) package. This component is classified as Active and carries AEC-Q101 automotive qualification with ROHS3 compliance. Zener diodes of this specification are used in voltage regulation, overvoltage protection, and reference voltage applications across automotive and industrial electronics. Substitute parts become necessary due to inventory constraints, supply chain disruptions, or design flexibility requirements while maintaining equivalent electrical and mechanical performance.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	18	V
Power - Maximum	500	mW
Operating Temperature Range	-65 to 175	°C
Mounting Type	Through Hole	—
Package / Case	DO-204AH, DO-35, Axial	—
Voltage - Forward (Max) @ If	1.5 V @ 200 mA	V @ mA

Substitute Part Grouping Explanation

Substitution of the TZX18C-TAP is permissible with components meeting the following criteria:

Critical Matching Parameters:

Zener voltage nominal rating of 18 V
Maximum power dissipation of 500 mW
Through-hole mounting configuration
DO-35 (DO-204AH) axial package format
Forward voltage maximum of 1.5 V at 200 mA
Operating temperature range encompassing -65°C to 175°C minimum

Acceptable Variation Parameters:

Zener voltage tolerance (±5% acceptable)
Impedance (Zzt) variation within device specifications
Reverse leakage current specifications
Compliance certifications and RoHS status

The substitute parts 1N5248B and BZX79C18-T50A satisfy all critical matching parameters and are electrically and mechanically interchangeable with the TZX18C-TAP in standard circuit applications.

Parameter Comparison

Parameter	TZX18C-TAP (Vishay)	1N5248B (Microchip)	BZX79C18-T50A (Fairchild)
Voltage - Zener (Nom)	18 V	18 V	18 V
Tolerance	—	±5%	±5%
Power - Max	500 mW	500 mW	500 mW
Impedance (Max) (Zzt)	55 Ohms	21 Ohms	45 Ohms
Current - Reverse Leakage @ Vr	1 µA @ 13 V	100 nA @ 14 V	50 nA @ 12.6 V
Voltage - Forward (Vf) (Max) @ If	1.5 V @ 200 mA	1.5 V @ 200 mA	1.5 V @ 100 mA
Operating Temperature	-65°C to 175°C	-65°C to 175°C	-65°C to 200°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial

Engineering Selection Recommendations

TZX18C-TAP (Vishay General Semiconductor)

Select this part for applications requiring AEC-Q101 automotive qualification and ROHS3 compliance. The TZX18C-TAP is the primary specification and carries active product status with established supply availability (929 pcs in stock). This part is suitable for automotive-grade circuit designs where compliance certifications are mandatory.

1N5248B (Microchip Technology)

This substitute is suitable for general-purpose applications where automotive qualification is not required. The 1N5248B offers superior impedance characteristics (21 Ohms versus 55 Ohms) and lower reverse leakage current (100 nA versus 1 µA), resulting in tighter voltage regulation performance. However, this part is RoHS non-compliant and lacks automotive qualification. Extensive inventory availability (62,638 pcs) supports high-volume applications. Operating temperature range matches the primary part at -65°C to 175°C.

BZX79C18-T50A (Fairchild Semiconductor)

This substitute provides an extended operating temperature range to 200°C, exceeding the primary part specification. The BZX79C18-T50A demonstrates moderate impedance (45 Ohms) and low reverse leakage (50 nA), offering balanced performance characteristics. This part is suitable for high-temperature environments where the extended thermal range provides design margin. Inventory availability is substantial (45,987 pcs). Product status is active with REACH unaffected designation.

Frequently Asked Questions (FAQ)

Q: Can 1N5248B replace TZX18C-TAP in automotive applications?

A: The 1N5248B is electrically compatible and mechanically interchangeable in the DO-35 package. However, it lacks AEC-Q101 automotive qualification and is RoHS non-compliant. Use only in non-automotive applications or where automotive certification is not a design requirement.

Q: What is the primary difference between the three parts?

A: All three parts share identical 18 V nominal Zener voltage and 500 mW power rating in DO-35 packages. The TZX18C-TAP provides automotive qualification; 1N5248B offers superior impedance and leakage characteristics; BZX79C18-T50A extends the operating temperature to 200°C.

Q: Are there package compatibility concerns?

A: All three parts use the DO-35 (DO-204AH) axial through-hole package. Physical dimensions and pin configurations are identical, permitting direct board-level substitution without layout modifications.

Q: Which substitute has the best voltage regulation performance?

A: The 1N5248B exhibits the lowest impedance (21 Ohms) and reverse leakage current (100 nA), providing superior voltage regulation stability. The BZX79C18-T50A offers intermediate performance (45 Ohms impedance, 50 nA leakage).

Q: Can BZX79C18-T50A be used in place of TZX18C-TAP for high-temperature circuits?

A: Yes. The BZX79C18-T50A is electrically and mechanically compatible and provides an extended operating temperature range to 200°C. This part is suitable for applications exceeding the TZX18C-TAP's 175°C maximum rating.

Q: What compliance certifications apply to each part?

A: TZX18C-TAP carries AEC-Q101 automotive qualification and ROHS3 compliance. 1N5248B is RoHS non-compliant and lacks automotive certification. BZX79C18-T50A has REACH unaffected status but lacks automotive qualification documentation in the provided specifications.

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