MMBZ5259B-7 Zener Diode 39V 350mW SOT-23-3 Equivalent & Substitute Parts

Part Overview

The MMBZ5259B-7 is a surface-mount zener diode manufactured by Diodes Incorporated, rated for 39 V nominal zener voltage with 350 mW maximum power dissipation in a SOT-23-3 package. This part is discontinued at DiGi Electronics, necessitating identification of equivalent and substitute components that maintain electrical and mechanical compatibility for new designs or production continuity.

Key Parameters

Parameter	Value
Voltage - Zener (Nom)	39 V
Tolerance	±5%
Power - Max	350 mW
Impedance (Max)	80 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 30 V
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA
Operating Temperature	-65°C ~ 150°C
Mounting Type	Surface Mount
Package / Case	TO-236-3, SC-59, SOT-23-3

Substitute Part Grouping Explanation

Substitution of the MMBZ5259B-7 is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 39 V nominal
Tolerance: ±5%
Package: SOT-23-3 (TO-236-3, SC-59)
Mounting type: Surface Mount
Operating temperature range: -65°C ~ 150°C

Secondary Substitution Criteria:

Power dissipation rating (350 mW primary; lower ratings acceptable if circuit design permits)
Impedance (80 Ohms nominal; variations acceptable within application requirements)
Reverse leakage current (100 nA @ 30 V; lower values acceptable)
Forward voltage (900 mV @ 10 mA; consistent across all candidates)

Substitute parts are grouped into two categories:

Category 1: Parametric Equivalents (350 mW Power Rating) Parts with identical 350 mW power rating and 80 Ohm impedance, providing direct replacement capability.

Category 2: Functional Substitutes (Reduced Power Rating) Parts with lower power ratings (225–300 mW) that maintain 39 V zener voltage and SOT-23-3 package, suitable for applications where maximum power dissipation does not exceed the substitute part rating.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Leakage @ Vr	Product Status	RoHS
MMBZ5259B-7	Diodes Inc.	39 V	±5%	350 mW	80 Ω	100 nA @ 30 V	Discontinued	Non-compliant
MMBZ5259B-7-F	Diodes Inc.	39 V	±5%	350 mW	80 Ω	100 nA @ 30 V	Active	ROHS3 Compliant
CMPZ5259B TR PBFREE	Central Semiconductor	39 V	±5%	350 mW	80 Ω	100 nA @ 30 V	Active	ROHS3 Compliant
BZX84C39-7-F	Diodes Inc.	39 V	±5%	300 mW	130 Ω	100 nA @ 27.3 V	Active	ROHS3 Compliant
BZX84-A39,215	NXP USA Inc.	39 V	±1%	250 mW	130 Ω	50 nA @ 27.3 V	Active	Not specified
BZX84C39LT1G	onsemi	39 V	±5%	225 mW	130 Ω	50 nA @ 27.3 V	Active	ROHS3 Compliant
MMBZ5259BLT1G	onsemi	39 V	±5%	225 mW	80 Ω	100 nA @ 30 V	Active	ROHS3 Compliant
SZBZX84C39ET1G	onsemi	39 V	±5%	225 mW	130 Ω	50 nA @ 27.3 V	Active	ROHS3 Compliant
SZMMBZ5259BLT1G	onsemi	39 V	±5%	225 mW	80 Ω	100 nA @ 30 V	Active	ROHS3 Compliant

Engineering Selection Recommendations

Direct Replacement (Parametric Equivalents):

MMBZ5259B-7-F and CMPZ5259B TR PBFREE provide complete parametric equivalence with the original MMBZ5259B-7. Both parts maintain 350 mW power rating, 80 Ohm impedance, and identical electrical characteristics. MMBZ5259B-7-F is manufactured by Diodes Incorporated (original manufacturer) and carries ROHS3 compliance. CMPZ5259B TR PBFREE is manufactured by Central Semiconductor Corp and also carries ROHS3 compliance. Both are in active production status with substantial inventory availability.

Functional Substitutes (Reduced Power Rating):

BZX84C39-7-F, BZX84-A39,215, BZX84C39LT1G, MMBZ5259BLT1G, SZBZX84C39ET1G, and SZMMBZ5259BLT1G maintain the 39 V zener voltage and SOT-23-3 package with power ratings between 225–300 mW. These parts are suitable for applications where circuit design does not require the full 350 mW dissipation capability.

Automotive-Grade Options:

BZX84-A39,215, SZBZX84C39ET1G, and SZMMBZ5259BLT1G carry AEC-Q101 automotive qualification. These parts are appropriate for automotive and high-reliability applications.

Compliance Considerations:

All substitute parts listed carry ROHS3 compliance status, addressing environmental and regulatory requirements. The original MMBZ5259B-7 is RoHS non-compliant; substitution with compliant alternatives aligns with current manufacturing standards.

Frequently Asked Questions (FAQ)

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

A: Yes. MMBZ5259B-7-F is a parametric equivalent with identical electrical specifications (39 V, 350 mW, 80 Ohm impedance) and package (SOT-23-3). The primary difference is product status (active vs. discontinued) and RoHS compliance (ROHS3 vs. non-compliant).

Q: What is the difference between 350 mW and 225 mW power-rated parts?

A: Power rating indicates maximum continuous power dissipation. A 225 mW part dissipates less heat and is suitable for lower-power applications. Selection depends on circuit design requirements. If the application requires sustained power dissipation exceeding 225 mW, a 350 mW part is necessary.

Q: Are parts with ±1% tolerance (BZX84-A39,215) interchangeable with ±5% tolerance parts?

A: ±1% tolerance parts are tighter specifications and are interchangeable in applications designed for ±5% tolerance. However, the reverse is not true. If circuit design requires ±1% tolerance, only BZX84-A39,215 meets this requirement.

Q: What does impedance (Zzt) variation mean for substitution?

A: Impedance affects dynamic zener voltage regulation. The original part specifies 80 Ohm maximum impedance. Substitute parts with 130 Ohm impedance exhibit slightly higher dynamic resistance. This affects voltage regulation performance in high-frequency or high-current switching applications. For general-purpose zener regulation, 130 Ohm impedance is acceptable.

Q: Can I use automotive-grade parts (AEC-Q101) in non-automotive applications?

A: Yes. Automotive-grade parts meet higher reliability and qualification standards and are suitable for any application. Automotive qualification does not restrict use to automotive circuits.

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

A: Reverse leakage current (specified at different voltages across parts) indicates diode quality and temperature stability. Lower leakage current (50 nA vs. 100 nA) indicates better performance. Parts with lower leakage are suitable for precision applications; higher leakage parts are acceptable for general-purpose regulation.

Q: Are all substitute parts available in the same packaging format?

A: All substitute parts use SOT-23-3 package (TO-236-3, SC-59). Packaging format is consistent across all candidates. Tape & Reel (TR) and Cut Tape (CT) packaging options affect supply chain logistics but not electrical or mechanical compatibility.

Q: Which substitute part offers the best overall compatibility?

A: MMBZ5259B-7-F offers the highest compatibility as a direct parametric equivalent from the original manufacturer (Diodes Incorporated) with identical electrical specifications and active production status. CMPZ5259B TR PBFREE provides equivalent performance from an alternative manufacturer.

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