MMBZ5259B-E3-18 Equivalent & Substitute Parts

Part Overview

The MMBZ5259B-E3-18 is a 39 V Zener diode rated at 225 mW in a surface mount SOT-23-3 package, manufactured by Vishay General Semiconductor - Diodes Division. This component is classified as obsolete, which necessitates identification of equivalent substitute parts for ongoing design requirements and procurement needs. Substitute parts must maintain electrical compatibility across voltage regulation, power dissipation, and thermal operating ranges while conforming to the same physical package specifications.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	39	V
Tolerance	±5%	%
Power - Maximum	225	mW
Impedance (Maximum)	80	Ohms
Current - Reverse Leakage @ Vr	100	nA @ 30 V
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the MMBZ5259B-E3-18 is determined by the following critical parameters:

Electrical Compatibility Requirements:

Zener voltage (Vz) must equal 39 V nominal with ±5% tolerance
Reverse leakage current must not exceed 100 nA @ 30 V
Impedance (Zzt) maximum of 80 Ohms or equivalent performance
Operating temperature range must encompass -55°C to 150°C minimum

Physical & Packaging Requirements:

Surface mount configuration in SOT-23-3 package (TO-236-3, SC-59)
Moisture sensitivity level MSL 1 (Unlimited)

Regulatory & Compliance Requirements:

ROHS3 compliance mandatory
REACH unaffected status
EAR99 export classification

Power Dissipation Consideration: Substitute parts rated at 225 mW or higher are functionally equivalent. Parts exceeding 225 mW (such as 350 mW variants) provide enhanced thermal margin and are direct substitutes when circuit design permits higher power ratings.

Parameter Comparison

Parameter	MMBZ5259B-E3-18 (Main)	CMPZ5259B BK PBFREE	CZRT55C39-G	MMBZ5259B-7-F	SZBZX84C39ET1G
Manufacturer	Vishay	Central Semiconductor	Comchip Technology	Diodes Incorporated	onsemi
Voltage - Zener (Nom)	39 V	39 V	39 V	39 V	39 V
Tolerance	±5%	±5%	±5%	±5%	±5%
Power - Max	225 mW	350 mW	350 mW	350 mW	225 mW
Impedance (Max)	80 Ω	80 Ω	130 Ω	80 Ω	130 Ω
Current - Reverse Leakage @ Vr	100 nA @ 30 V	100 nA @ 30 V	100 nA @ 27.3 V	100 nA @ 30 V	50 nA @ 27.3 V
Operating Temperature	-55 to 150°C	-65 to 150°C	-65 to 150°C	-65 to 150°C	-65 to 150°C
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Primary Substitute: MMBZ5259B-7-F (Diodes Incorporated)

The MMBZ5259B-7-F is the recommended substitute. It maintains identical electrical specifications to the main part (39 V, ±5%, 225 mW equivalent performance through 350 mW rating, 80 Ω impedance, 100 nA reverse leakage). The part is active in production with 17,300 units in stock, ensuring supply continuity. It carries ROHS3 compliance and is available in Tape & Reel packaging. The extended operating temperature range (-65°C to 150°C) provides additional thermal margin compared to the original part.

Secondary Substitutes: CMPZ5259B BK PBFREE and CZRT55C39-G

Both parts are active alternatives with 350 mW power ratings, providing enhanced thermal performance. CMPZ5259B BK PBFREE (Central Semiconductor) maintains 80 Ω impedance matching. CZRT55C39-G (Comchip Technology) features 130 Ω impedance with Tape & Reel packaging. Both support the full operating temperature range and carry ROHS3 compliance.

Automotive-Grade Alternative: SZBZX84C39ET1G (onsemi)

The SZBZX84C39ET1G is an AEC-Q101 qualified automotive-grade Zener diode with 225 mW power rating matching the original specification. It features lower reverse leakage (50 nA @ 27.3 V) and 130 Ω impedance. This part is suitable for applications requiring automotive qualification and is active in production with 3,802 units in stock.

All substitute parts conform to ROHS3 requirements, maintain MSL 1 moisture sensitivity, and are classified as REACH unaffected with EAR99 export status.

Frequently Asked Questions (FAQ)

Q: Can MMBZ5259B-7-F replace MMBZ5259B-E3-18 in existing designs?

A: Yes. The MMBZ5259B-7-F maintains the same 39 V nominal Zener voltage, ±5% tolerance, 80 Ω impedance, and 100 nA reverse leakage specification. The 350 mW power rating exceeds the original 225 mW specification, providing additional thermal margin. Both parts use identical SOT-23-3 packaging and are ROHS3 compliant.

Q: What is the difference between 225 mW and 350 mW rated Zener diodes?

A: Power rating indicates maximum continuous power dissipation capability. A 350 mW part can safely dissipate more heat than a 225 mW part. In substitution, a higher-rated part (350 mW) is functionally equivalent to a lower-rated part (225 mW) when the circuit design does not exceed the original power specification. The higher rating provides thermal headroom.

Q: Are all substitute parts available in the same package?

A: Yes. All substitute parts listed are available in SOT-23-3 (TO-236-3, SC-59) surface mount package. Physical dimensions and pin configurations are identical, enabling direct board-level substitution without layout modifications.

Q: Why is SZBZX84C39ET1G listed separately?

A: SZBZX84C39ET1G is AEC-Q101 automotive qualified, making it suitable for applications requiring automotive-grade components. It maintains 225 mW power rating and 39 V specification but features lower reverse leakage (50 nA) and higher impedance (130 Ω). Selection depends on application requirements and automotive qualification necessity.

Q: What does ROHS3 compliance mean for this component?

A: ROHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements, restricting lead, cadmium, mercury, and other hazardous materials. All listed substitute parts carry ROHS3 compliance, ensuring regulatory conformance for commercial and industrial applications.

Q: Can impedance differences affect circuit performance?

A: Impedance (Zzt) affects dynamic response characteristics. The main part and MMBZ5259B-7-F both specify 80 Ω impedance. CZRT55C39-G and SZBZX84C39ET1G specify 130 Ω impedance. In most voltage regulation applications, this difference is negligible. Circuit-specific analysis is required only for high-frequency or precision regulation applications.

Q: What is the significance of reverse leakage current specifications?

A: Reverse leakage current indicates the small current flowing through the Zener diode when reverse biased below the Zener voltage. Lower leakage (50 nA vs. 100 nA) reduces standby power consumption. All listed parts meet or exceed the original 100 nA specification, ensuring equivalent or superior performance.

Q: Are there inventory considerations for substitute selection?

A: MMBZ5259B-7-F has the highest inventory (17,300 units), ensuring immediate availability. SZBZX84C39ET1G (3,802 units), CMPZ5259B BK PBFREE (1,029 units), and CZRT55C39-G (1,010 units) are also in stock. Inventory levels support production requirements across all substitute options.

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