MMBZ5239B Zener Diode 9.1V 350mW SOT-23-3 Equivalent & Substitute Parts

Part Overview

The MMBZ5239B is a surface mount Zener diode manufactured by onsemi, rated at 9.1V nominal Zener voltage with 350mW maximum power dissipation in a SOT-23-3 package. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The MMBZ5239B serves voltage regulation and protection applications requiring precise 9.1V reference characteristics with ±5% tolerance in compact surface mount form factor.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	9.1	V
Tolerance	±5%	-
Power - Max	350	mW
Impedance (Max)	10	Ohms
Current - Reverse Leakage @ Vr	3 µA @ 7V	-
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	-
Operating Temperature	-55°C ~ 150°C	-
Mounting Type	Surface Mount	-
Package / Case	TO-236-3, SC-59, SOT-23-3	-
Moisture Sensitivity Level	1 (Unlimited)	-

Substitute Part Grouping Explanation

Substitution of the MMBZ5239B is determined by the following critical parameters:

Mandatory Matching Parameters:

Voltage - Zener (Nom): 9.1V
Package / Case: SOT-23-3 (TO-236-3, SC-59)
Mounting Type: Surface Mount

Allowable Variation Parameters:

Power - Max: The MMBZ5239B specifies 350mW. Substitute parts rated at 225mW are acceptable for applications where power dissipation does not exceed 225mW. Parts with equal or higher power ratings are direct substitutes.
Tolerance: The MMBZ5239B specifies ±5%. Parts with ±2% tolerance are acceptable as they provide tighter voltage regulation. Parts with ±5% tolerance are direct equivalents.
Impedance (Max): The MMBZ5239B specifies 10 Ohms. Parts with impedance up to 15 Ohms are acceptable substitutes.
Operating Temperature: The MMBZ5239B specifies -55°C ~ 150°C. Parts with extended range (-65°C ~ 150°C) are acceptable.
Current - Reverse Leakage: The MMBZ5239B specifies 3 µA @ 7V. Parts with lower leakage (500 nA @ 6V) are acceptable.

Product Status Consideration: The MMBZ5239B is obsolete. Active substitute parts are preferred for new designs and ongoing procurement. Automotive-grade variants with AEC-Q101 qualification provide additional reliability assurance for critical applications.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Vf (Max) @ If	Temp Range	Product Status	Grade	RoHS
MMBZ5239B	onsemi	9.1V	±5%	350mW	10Ω	900mV @ 10mA	-55°C ~ 150°C	Obsolete	Commercial	-
BZX84B9V1LT1G	onsemi	9.1V	±2%	225mW	15Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Commercial	ROHS3
MMBZ5239BLT1G	onsemi	9.1V	±5%	225mW	10Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Commercial	ROHS3
MMBZ5239ELT1G	onsemi	9.1V	-	225mW	-	-	-	Active	Commercial	ROHS3
SZBZX84B9V1LT1G	onsemi	9.1V	±2%	225mW	15Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Automotive	ROHS3
SZBZX84C9V1ET1G	onsemi	9.1V	±5%	225mW	15Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Automotive	ROHS3
SZBZX84C9V1ET3G	onsemi	9.1V	±5%	225mW	15Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Automotive	ROHS3
SZBZX84C9V1LT1G	onsemi	9.1V	±5%	225mW	15Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Automotive	ROHS3
SZBZX84C9V1LT3G	onsemi	9.1V	±5%	225mW	15Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Automotive	ROHS3
SZMMBZ5239BLT1G	onsemi	9.1V	±5%	225mW	10Ω	900mV @ 10mA	-65°C ~ 150°C	Active	Automotive	ROHS3
SZMMBZ5239ELT1G	onsemi	9.1V	±5%	225mW	10Ω	900mV @ 10mA	-55°C ~ 150°C	Active	Automotive	ROHS3

Engineering Selection Recommendations

For Commercial Applications (Non-Automotive):

MMBZ5239BLT1G is the primary direct substitute. It maintains the same base part number (MMBZ5239), identical Zener voltage (9.1V), matching impedance (10Ω), and equivalent tolerance (±5%). The reduction from 350mW to 225mW is acceptable for applications where thermal dissipation does not exceed 225mW. This part is active and ROHS3 compliant.

BZX84B9V1LT1G offers tighter voltage tolerance (±2%) with extended operating temperature range (-65°C ~ 150°C). The increased impedance (15Ω vs 10Ω) and reduced power rating (225mW) are acceptable for most voltage regulation circuits. This part is active and ROHS3 compliant.

For Automotive Applications (AEC-Q101 Required):

SZMMBZ5239BLT1G is the automotive-grade equivalent of MMBZ5239BLT1G. It provides identical electrical characteristics (9.1V, ±5%, 10Ω impedance, 225mW) with AEC-Q101 qualification and extended temperature range (-65°C ~ 150°C). This part is active and ROHS3 compliant.

SZBZX84B9V1LT1G provides automotive-grade performance with tighter tolerance (±2%) and extended temperature range. The increased impedance (15Ω) is acceptable for automotive voltage regulation applications. This part is active and ROHS3 compliant.

SZBZX84C9V1ET1G, SZBZX84C9V1ET3G, SZBZX84C9V1LT1G, and SZBZX84C9V1LT3G are automotive-grade variants with ±5% tolerance matching the original MMBZ5239B specification. All are active, ROHS3 compliant, and AEC-Q101 qualified.

For Extended Temperature Range Applications:

SZMMBZ5239ELT1G maintains the original operating temperature range (-55°C ~ 150°C) while providing automotive-grade qualification. This part is active and ROHS3 compliant.

All substitute parts maintain SOT-23-3 package compatibility and surface mount mounting type. Selection should be based on application power dissipation requirements, automotive qualification necessity, and tolerance specifications.

Frequently Asked Questions (FAQ)

Q: Can MMBZ5239BLT1G replace MMBZ5239B in all applications?

A: MMBZ5239BLT1G is a direct substitute for applications where power dissipation does not exceed 225mW. The original MMBZ5239B is rated for 350mW. If your circuit dissipates more than 225mW in the Zener diode, thermal analysis is required to confirm the substitute is suitable. Both parts share identical Zener voltage (9.1V), tolerance (±5%), impedance (10Ω), and SOT-23-3 package.

Q: What is the difference between commercial and automotive-grade parts?

A: Automotive-grade parts (SZBZX84 and SZMMBZ5239 series) carry AEC-Q101 qualification, indicating compliance with automotive reliability standards. These parts undergo additional qualification testing and are suitable for automotive applications. Commercial-grade parts (MMBZ5239 and BZX84 series) are suitable for general industrial and consumer applications. Selection depends on application requirements.

Q: Why do some substitute parts have ±2% tolerance instead of ±5%?

A: BZX84B9V1LT1G and SZBZX84B9V1LT1G offer ±2% tolerance, providing tighter voltage regulation compared to the original MMBZ5239B (±5%). Tighter tolerance is beneficial for precision voltage reference applications but is not required for all circuits. Both tolerance levels are acceptable substitutes as long as circuit design accommodates the specified tolerance range.

Q: Are all substitute parts ROHS3 compliant?

A: Yes, all listed substitute parts are ROHS3 compliant. The original MMBZ5239B does not specify RoHS status. All active substitute parts meet current environmental compliance requirements.

Q: What is the significance of impedance differences (10Ω vs 15Ω)?

A: Impedance affects the dynamic response of the Zener diode to load transients. The original MMBZ5239B specifies 10Ω maximum impedance. Substitute parts with 15Ω impedance (BZX84B9V1LT1G and SZBZX84 series) have slightly higher impedance. For most voltage regulation applications, this difference is acceptable. High-speed transient applications may require impedance verification.

Q: Can I use MMBZ5239ELT1G as a substitute?

A: MMBZ5239ELT1G maintains 9.1V Zener voltage and SOT-23-3 package compatibility. However, detailed electrical parameters (tolerance, impedance, leakage current) are not fully specified in available data. MMBZ5239BLT1G is the preferred substitute with complete parameter documentation.

Q: What is the difference between SZBZX84C9V1ET1G and SZBZX84C9V1LT1G?

A: Both parts are automotive-grade Zener diodes with identical electrical specifications (9.1V, ±5%, 225mW, 15Ω impedance). The designation difference (ET vs LT) indicates different manufacturing or packaging variants. Both are active and suitable for automotive applications. Consult the manufacturer datasheet for specific packaging or lead configuration differences.

Q: Is the temperature range difference (-55°C vs -65°C) significant?

A: The original MMBZ5239B operates from -55°C to 150°C. Most substitute parts extend the lower limit to -65°C, providing wider operating range. For applications operating above -55°C, both ranges are equivalent. For applications requiring operation below -55°C, extended-range substitutes are necessary.

Q: Can I substitute a 225mW part for a 350mW part in high-power applications?

A: No. If your application requires 350mW power dissipation capability, a 225mW substitute is not suitable. Thermal analysis must confirm that actual power dissipation in the circuit does not exceed 225mW. Exceeding the rated power dissipation will cause device failure.

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