VLZ33D-GS18 Equivalent & Substitute Parts

Part Overview

The VLZ33D-GS18 is a Zener diode rated at 32.3 V nominal voltage with 500 mW power dissipation in a SOD-80 QuadroMELF surface mount package, manufactured by Vishay General Semiconductor - Diodes Division. This component is classified as Obsolete, necessitating identification of equivalent substitute parts for ongoing design requirements and procurement needs. The part carries AEC-Q101 automotive qualification and ROHS3 compliance.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	32.3	V
Power - Max	500	mW
Impedance (Max)	65	Ohms
Current - Reverse Leakage @ Vr	40	µA @ 29.9 V
Voltage - Forward (Vf) (Max) @ If	1.5	V @ 200 mA
Operating Temperature Range	-65 to 175	°C
Mounting Type	Surface Mount	-
Package / Case	SOD-80 Variant	-
Grade	Automotive	-
Qualification	AEC-Q101	-

Substitute Part Grouping Explanation

Substitution of the VLZ33D-GS18 is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage nominal rating within acceptable circuit tolerance
Power dissipation capacity of 500 mW minimum
Surface mount package compatibility
Operating temperature range of -65°C to 175°C
Reverse leakage current characteristics
Forward voltage drop characteristics

Substitution Logic:

The TLZ33D-GS18 qualifies as a direct manufacturer substitute from Vishay, offering identical power rating (500 mW) and operating temperature range, with nominal Zener voltage of 33 V (compared to 32.3 V of the main part). Both devices utilize SOD-80 surface mount packages and maintain equivalent impedance specifications at 65 Ohms maximum. The TLZ33D-GS18 is Active product status, addressing the obsolescence of the VLZ33D-GS18.

The 1N4121UR-1 from Microchip Technology provides functional equivalence with 33 V nominal Zener voltage and 500 mW power rating. This part operates within the same temperature range and utilizes a surface mount package (DO-213AA). However, it exhibits different package geometry (DO-213AA versus SOD-80), higher impedance (200 Ohms maximum), and does not carry AEC-Q101 automotive qualification. The 1N4121UR-1 is RoHS non-compliant, whereas the main part and primary substitute maintain ROHS3 compliance.

Parameter Comparison

Parameter	VLZ33D-GS18	TLZ33D-GS18	1N4121UR-1
Manufacturer	Vishay General Semiconductor	Vishay General Semiconductor	Microchip Technology
Voltage - Zener (Nom)	32.3 V	33 V	33 V
Power - Max	500 mW	500 mW	500 mW
Impedance (Max)	65 Ohms	65 Ohms	200 Ohms
Current - Reverse Leakage @ Vr	40 µA @ 29.9 V	40 nA @ 29.9 V	10 nA @ 25.1 V
Voltage - Forward (Vf) (Max) @ If	1.5 V @ 200 mA	1.5 V @ 200 mA	1.1 V @ 200 mA
Operating Temperature Range	-65 to 175 °C	-65 to 175 °C	-65 to 175 °C
Mounting Type	Surface Mount	Surface Mount	Surface Mount
Package / Case	SOD-80 QuadroMELF	SOD-80 MiniMELF	DO-213AA
Product Status	Obsolete	Active	Active
Grade	Automotive	-	-
Qualification	AEC-Q101	-	-
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant

Engineering Selection Recommendations

TLZ33D-GS18 Selection:

The TLZ33D-GS18 is the primary substitute for the VLZ33D-GS18. Both parts originate from the same manufacturer (Vishay General Semiconductor - Diodes Division) and maintain identical electrical specifications for power dissipation (500 mW), impedance (65 Ohms maximum), and operating temperature range (-65°C to 175°C). The TLZ33D-GS18 carries Active product status, ensuring long-term availability and supply chain continuity. Both parts maintain ROHS3 compliance and REACH Unaffected status. The nominal Zener voltage difference (33 V versus 32.3 V) represents a 2.2% variance, which falls within typical circuit tolerance margins for voltage regulation applications. The TLZ33D-GS18 is packaged in SOD-80 MiniMELF format, compatible with existing PCB layouts designed for SOD-80 variants. The reverse leakage current specification improves from 40 µA to 40 nA, indicating superior device performance.

1N4121UR-1 Selection:

The 1N4121UR-1 from Microchip Technology provides functional equivalence in applications where package geometry flexibility exists. This part maintains identical power rating (500 mW), operating temperature range (-65°C to 175°C), and nominal Zener voltage (33 V). However, the 1N4121UR-1 exhibits three significant deviations: (1) DO-213AA package geometry differs from SOD-80, requiring PCB layout modification; (2) impedance specification of 200 Ohms exceeds the 65 Ohms maximum of the main part, affecting voltage regulation characteristics; (3) RoHS non-compliance status conflicts with ROHS3 requirements of the original design. The 1N4121UR-1 does not carry automotive qualification or AEC-Q101 certification. Selection of this part is appropriate only for non-automotive applications where RoHS compliance is not mandated and circuit impedance tolerance permits the higher specification.

Frequently Asked Questions (FAQ)

Q: Can the TLZ33D-GS18 directly replace the VLZ33D-GS18 without PCB modification?

A: The TLZ33D-GS18 utilizes SOD-80 MiniMELF packaging, while the VLZ33D-GS18 uses SOD-80 QuadroMELF packaging. Both are SOD-80 variants with compatible footprints for surface mount assembly. Verification of specific PCB pad dimensions against both package specifications is required to confirm direct compatibility without layout modification.

Q: What is the significance of the 32.3 V versus 33 V Zener voltage difference?

A: The 0.7 V difference represents a 2.2% variance in nominal Zener voltage. Circuit performance depends on the specific voltage regulation tolerance required by the application. For applications with ±5% or greater tolerance bands, this variance is acceptable. Applications requiring tighter voltage regulation must evaluate circuit-level impact through simulation or testing.

Q: Why does the 1N4121UR-1 have higher impedance (200 Ohms versus 65 Ohms)?

A: Impedance specification reflects the dynamic resistance of the Zener diode at operating current. Higher impedance results in greater voltage variation across the device with changes in load current. Applications requiring stable voltage regulation benefit from lower impedance devices. The 1N4121UR-1 is suitable for applications with less stringent voltage stability requirements.

Q: Is the 1N4121UR-1 suitable for automotive applications?

A: The 1N4121UR-1 does not carry AEC-Q101 automotive qualification and is RoHS non-compliant. Automotive applications requiring AEC-Q101 certification must utilize the TLZ33D-GS18, which maintains both automotive qualification and ROHS3 compliance.

Q: What is the impact of reverse leakage current differences among these parts?

A: Reverse leakage current affects power consumption and circuit performance in high-impedance applications. The VLZ33D-GS18 specifies 40 µA reverse leakage, while the TLZ33D-GS18 and 1N4121UR-1 specify 40 nA and 10 nA respectively. Lower reverse leakage reduces standby power consumption and improves circuit efficiency. The TLZ33D-GS18 provides a 1000-fold improvement over the original part.

Q: Can these parts be used interchangeably in existing designs?

A: Interchangeability depends on specific circuit requirements and PCB layout constraints. The TLZ33D-GS18 offers the highest compatibility due to identical electrical specifications and package family. The 1N4121UR-1 requires evaluation of impedance tolerance, package geometry compatibility, and compliance requirements before substitution.

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