BZX84B33-E3-18 Equivalent & Substitute Parts

Part Overview

The BZX84B33-E3-18 is a 33 V Zener diode manufactured by Vishay General Semiconductor - Diodes Division, rated for 300 mW power dissipation in a surface mount SOT-23-3 package. This component is classified as Active product status and is RoHS3 compliant. Equivalent and substitute parts are identified to support design flexibility, supply chain continuity, and application-specific requirements where alternative electrical or mechanical characteristics may be acceptable within defined parameters.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	33	V
Tolerance	±2%	—
Power - Maximum	300	mW
Impedance (Maximum)	80	Ohms
Current - Reverse Leakage @ Vr	50	nA @ 23.1 V
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOT-23-3	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the BZX84B33-E3-18 is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 33 V nominal
Package type: SOT-23-3 (TO-236-3, SC-59)
Mounting: Surface mount
Compliance: RoHS3 compliant

Secondary Compatibility Parameters:

Power rating: 300 mW or greater
Tolerance: ±2% to ±6% acceptable
Impedance: 58 to 80 Ohms maximum
Reverse leakage: 50 to 100 nA @ specified voltage
Operating temperature: -55°C to -65°C minimum; 150°C maximum

Substitute parts are grouped into two categories:

Category A - Direct SOT-23-3 Substitutes (Same Package): Parts maintaining the SOT-23-3 package configuration with 33 V nominal zener voltage and compatible electrical parameters.

Category B - Alternative Package Substitutes (Different Package): Parts with 33 V nominal zener voltage but different surface mount packages (SOT-323, SOT-363), suitable only when package footprint change is acceptable.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Ir @ Vr	Temp Range	Package	Grade
BZX84B33-E3-18	Vishay	33 V	±2%	300 mW	80 Ω	50 nA @ 23.1 V	-55 to 150°C	SOT-23-3	—
BZX84B33Q-7-F	Diodes Inc.	33 V	±2%	300 mW	80 Ω	100 nA @ 23.1 V	-65 to 150°C	SOT-23-3	Automotive (AEC-Q101)
BZX84C33LT1G	onsemi	33 V	±6%	225 mW	80 Ω	50 nA @ 23.1 V	-65 to 150°C	SOT-23-3	—
BZX84C33LT3G	onsemi	33 V	±6%	225 mW	80 Ω	50 nA @ 23.1 V	-65 to 150°C	SOT-23-3	—
CMPZ5257B TR PBFREE	Central Semiconductor	33 V	±5%	350 mW	58 Ω	100 nA @ 25 V	-65 to 150°C	SOT-23-3	—
MMBZ5257BTS-7-F	Diodes Inc.	33 V	±5%	200 mW	58 Ω	100 nA @ 25 V	-65 to 150°C	SOT-363	—
MMBZ5257BW-7-F	Diodes Inc.	33 V	±5%	200 mW	58 Ω	100 nA @ 25 V	-65 to 150°C	SOT-323	—
SZBZX84C33ET3G	onsemi	33 V	±6%	225 mW	80 Ω	50 nA @ 23.1 V	-65 to 150°C	SOT-23-3	Automotive (AEC-Q101)
SZMMBZ5257ELT1G	onsemi	33 V	±5%	225 mW	58 Ω	100 nA @ 25 V	-55 to 150°C	SOT-23-3	Automotive (AEC-Q101)

Engineering Selection Recommendations

Direct Substitutes (SOT-23-3 Package, Recommended Priority):

BZX84B33Q-7-F (Diodes Incorporated) — Maintains ±2% tolerance and 300 mW power rating. Extends minimum operating temperature to -65°C. Carries AEC-Q101 automotive qualification. Suitable for applications requiring tight tolerance specifications and extended temperature range.
CMPZ5257B TR PBFREE (Central Semiconductor) — Provides higher power rating (350 mW) with ±5% tolerance. Impedance reduced to 58 Ohms. Suitable for applications with higher thermal dissipation requirements or where tolerance relaxation is acceptable.
SZBZX84C33ET3G (onsemi) — Maintains 33 V nominal with ±6% tolerance and 225 mW power. AEC-Q101 automotive qualified. Suitable for automotive applications where component qualification is required.
SZMMBZ5257ELT1G (onsemi) — Provides ±5% tolerance with 225 mW power and 58 Ohm impedance. AEC-Q101 automotive qualified. Maintains -55°C minimum operating temperature matching the original part. Suitable for automotive applications with relaxed tolerance requirements.
BZX84C33LT1G and BZX84C33LT3G (onsemi) — Both offer ±6% tolerance with 225 mW power. Extend minimum operating temperature to -65°C. Suitable for cost-optimized designs where tolerance relaxation is acceptable.

Alternative Package Substitutes (Different Footprint):

MMBZ5257BW-7-F (Diodes Incorporated, SOT-323) — Reduces power rating to 200 mW with ±5% tolerance. Smaller footprint (SOT-323). Suitable only when PCB space constraints override power dissipation requirements.
MMBZ5257BTS-7-F (Diodes Incorporated, SOT-363) — Three independent 33 V zener diodes in SOT-363 package, each rated 200 mW. Suitable for multi-channel applications where integrated array configuration is beneficial.

Compliance Status: All substitute parts maintain RoHS3 compliance and REACH unaffected status. Selection should prioritize parts matching the original ±2% tolerance specification unless application requirements permit tolerance relaxation to ±5% or ±6%.

Frequently Asked Questions (FAQ)

Q: Can BZX84C33LT1G replace BZX84B33-E3-18 directly?

A: BZX84C33LT1G is compatible in SOT-23-3 package and maintains 33 V nominal zener voltage. However, tolerance widens from ±2% to ±6%, and power rating reduces from 300 mW to 225 mW. Substitution is acceptable only if the application tolerates ±6% voltage variation and operates below 225 mW dissipation.

Q: What is the difference between BZX84B33Q-7-F and SZBZX84C33ET3G?

A: BZX84B33Q-7-F maintains ±2% tolerance and 300 mW power rating with -65°C minimum temperature. SZBZX84C33ET3G provides ±6% tolerance and 225 mW power with -65°C minimum temperature. Both carry AEC-Q101 automotive qualification. BZX84B33Q-7-F is preferred for tight tolerance requirements; SZBZX84C33ET3G for cost-optimized automotive applications.

Q: Why does CMPZ5257B TR PBFREE have lower impedance (58 Ohms vs. 80 Ohms)?

A: Impedance variation is a characteristic difference between manufacturers and design approaches. The 58 Ohm impedance of CMPZ5257B remains within acceptable substitution parameters and does not prevent functional equivalence at 33 V nominal zener voltage.

Q: Can MMBZ5257BW-7-F be used as a direct replacement?

A: MMBZ5257BW-7-F uses SOT-323 package instead of SOT-23-3, requiring PCB layout modification. Power rating reduces to 200 mW. Substitution is possible only when package footprint change is acceptable and application power dissipation does not exceed 200 mW.

Q: What is the advantage of SZMMBZ5257ELT1G over other substitutes?

A: SZMMBZ5257ELT1G maintains the original -55°C minimum operating temperature (matching BZX84B33-E3-18) while providing AEC-Q101 automotive qualification. It offers ±5% tolerance with 225 mW power and 58 Ohm impedance, making it suitable for automotive applications requiring temperature range consistency.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed are RoHS3 compliant and REACH unaffected, matching the compliance status of the original BZX84B33-E3-18.

Q: Which substitute offers the highest power dissipation capability?

A: CMPZ5257B TR PBFREE provides the highest power rating at 350 mW, compared to the original 300 mW specification. This part is suitable for applications requiring additional thermal margin.

Q: Can MMBZ5257BTS-7-F be used in single-diode applications?

A: MMBZ5257BTS-7-F is a three-independent-diode array in SOT-363 package. While each diode is rated 33 V, using this part in single-diode applications results in unused diodes and inefficient PCB utilization. Direct SOT-23-3 substitutes are recommended for single-diode requirements.

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