MMBZ5238B Zener Diode Equivalent & Substitute Parts

Part Overview

The MMBZ5238B is a surface mount zener diode rated at 8.7 V nominal with 350 mW maximum power dissipation in a SOT-23-3 package. Manufactured by onsemi, this component is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active manufacturers are necessary for new designs and ongoing production requirements. Substitute parts maintain the core electrical specifications while offering active product status and improved availability.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	8.7	V
Tolerance	±5%	%
Power - Max	350	mW
Impedance (Max)	8	Ohms
Current - Reverse Leakage @ Vr	3	µA @ 6.5 V
Voltage - Forward (Vf) (Max) @ If	900	mV @ 10 mA
Operating Temperature	-55 to 150	°C
Mounting Type	Surface Mount
Package / Case	SOT-23-3
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the MMBZ5238B is determined by the following critical parameters:

Electrical Compatibility Requirements:

Voltage - Zener (Nom): 8.7 V ±5%
Impedance (Max): 8 Ohms
Current - Reverse Leakage @ Vr: 3 µA @ 6.5 V
Voltage - Forward (Vf) (Max) @ If: 900 mV @ 10 mA
Tolerance: ±5%

Mechanical Compatibility Requirements:

Mounting Type: Surface Mount
Package / Case: SOT-23-3 (TO-236-3, SC-59)
Moisture Sensitivity Level: 1 (Unlimited)

Substitution Categories:

Direct Equivalents (Same Zener Voltage, Same Power Rating): Parts with 8.7 V nominal zener voltage and 350 mW power rating in SOT-23-3 package maintain full electrical and mechanical compatibility.

Similar Equivalents (Same Zener Voltage, Lower Power Rating): Parts with 8.7 V nominal zener voltage but reduced power ratings (225 mW, 200 mW) are suitable for applications where the full 350 mW dissipation is not required.

Higher Power Rating Equivalents (Same Zener Voltage, Higher Power Rating): Parts with 8.7 V nominal zener voltage and power ratings exceeding 350 mW provide enhanced thermal capability.

Voltage Variant (Different Zener Voltage): The MMBZ5239B-7-F operates at 9.1 V nominal and is included for reference in applications requiring alternative voltage regulation.

Package Variant (Different Package Type): The MMBZ5238BS-7-F is a 2-independent zener diode array in SOT-363 package, suitable only for applications requiring multiple independent zener elements.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Vz (Nom)	Power (Max)	Zzt (Max)	Package	Product Status	Operating Temp	RoHS Status
MMBZ5238B	onsemi	8.7 V	350 mW	8 Ω	SOT-23-3	Obsolete	-55 to 150°C	Not Specified
MMBZ5238B-7-F	Diodes Incorporated	8.7 V	350 mW	8 Ω	SOT-23-3	Active	-65 to 150°C	ROHS3 Compliant
MMBZ5238BLT1G	onsemi	8.7 V	225 mW	8 Ω	SOT-23-3	Active	-65 to 150°C	ROHS3 Compliant
SZMMBZ5238BLT1G	onsemi	8.7 V	225 mW	8 Ω	SOT-23-3	Active	-65 to 150°C	ROHS3 Compliant
CMPZ5238B TR PBFREE	Central Semiconductor Corp	8.7 V	350 mW	8 Ω	SOT-23-3	Active	-65 to 150°C	ROHS3 Compliant
MMBZ5238BS-7-F	Diodes Incorporated	8.7 V	200 mW	8 Ω	SOT-363	Active	-65 to 150°C	ROHS3 Compliant
MMBZ5238B_R1_00001	Panjit International Inc.	8.7 V	410 mW	8 Ω	SOT-23-3	Active	-55 to 150°C	ROHS3 Compliant
MMBZ5238B-TP	Micro Commercial Co	8.7 V	350 mW	8 Ω	SOT-23-3	Active	-55 to 150°C	ROHS3 Compliant
MMBZ5239B-7-F	Diodes Incorporated	9.1 V	350 mW	10 Ω	SOT-23-3	Active	-65 to 150°C	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical and Mechanical Specifications):

MMBZ5238B-7-F (Diodes Incorporated) and CMPZ5238B TR PBFREE (Central Semiconductor Corp) are direct equivalents with 8.7 V nominal zener voltage, 350 mW power rating, and SOT-23-3 package. Both are active products with ROHS3 compliance. MMBZ5238B-7-F offers extended operating temperature range (-65 to 150°C) compared to the original part (-55 to 150°C). MMBZ5238B-TP (Micro Commercial Co) provides identical electrical specifications and maintains the original temperature range.

For Power-Constrained Applications:

MMBZ5238BLT1G and SZMMBZ5238BLT1G (both onsemi) maintain 8.7 V nominal zener voltage with reduced power dissipation of 225 mW. These parts are suitable for applications where thermal management is less demanding. SZMMBZ5238BLT1G includes AEC-Q101 automotive qualification for applications requiring automotive-grade components.

For Enhanced Thermal Performance:

MMBZ5238B_R1_00001 (Panjit International Inc.) provides 410 mW power rating with identical 8.7 V zener voltage and SOT-23-3 package, offering increased thermal headroom for high-dissipation applications.

For Multi-Element Requirements:

MMBZ5238BS-7-F (Diodes Incorporated) is a 2-independent zener diode array in SOT-363 package. This part is applicable only when circuit design requires multiple independent zener elements in a single package.

For Alternative Voltage Regulation:

MMBZ5239B-7-F (Diodes Incorporated) operates at 9.1 V nominal zener voltage with 350 mW power rating. This part is suitable only for applications requiring 9.1 V regulation instead of 8.7 V.

All recommended active substitutes carry ROHS3 compliance and unlimited moisture sensitivity rating (MSL 1), ensuring compatibility with modern manufacturing processes.

Frequently Asked Questions (FAQ)

Q: Can MMBZ5238BLT1G replace MMBZ5238B in all applications?

A: MMBZ5238BLT1G maintains identical zener voltage (8.7 V) and impedance (8 Ohms) but operates at 225 mW maximum power versus 350 mW for the original part. Substitution is valid only if the application's power dissipation requirement does not exceed 225 mW. Verify circuit current and voltage conditions before substitution.

Q: What is the difference between MMBZ5238BLT1G and SZMMBZ5238BLT1G?

A: Both parts are manufactured by onsemi with identical electrical specifications (8.7 V, 225 mW, SOT-23-3). SZMMBZ5238BLT1G includes AEC-Q101 automotive qualification, making it suitable for automotive applications. Standard MMBZ5238BLT1G is for general industrial and commercial use.

Q: Is MMBZ5238BS-7-F a direct substitute for MMBZ5238B?

A: No. MMBZ5238BS-7-F is a 2-independent zener diode array in SOT-363 package, fundamentally different from the single-element SOT-23-3 package of MMBZ5238B. This part is applicable only in circuit designs requiring multiple independent zener elements.

Q: Why does MMBZ5239B-7-F appear in the substitute list if it has different voltage?

A: MMBZ5239B-7-F operates at 9.1 V nominal zener voltage, not 8.7 V. This part is included for reference in applications where alternative voltage regulation is acceptable. Direct substitution is not recommended for circuits designed for 8.7 V regulation.

Q: What is the temperature range difference between MMBZ5238B and its active substitutes?

A: The original MMBZ5238B operates from -55 to 150°C. Most active substitutes (MMBZ5238B-7-F, MMBZ5238BLT1G, SZMMBZ5238BLT1G, CMPZ5238B TR PBFREE) extend the lower limit to -65°C. MMBZ5238B-TP and MMBZ5238B_R1_00001 maintain the -55°C lower limit. Verify application temperature requirements before selection.

Q: Are all substitute parts ROHS3 compliant?

A: All active substitute parts listed carry ROHS3 compliance. The original MMBZ5238B does not specify RoHS status due to its obsolete classification.

Q: Can MMBZ5238B-TP and MMBZ5238B-7-F be used interchangeably?

A: Both parts have identical electrical specifications (8.7 V, 350 mW, 8 Ohms impedance) and SOT-23-3 package. MMBZ5238B-7-F extends operating temperature to -65°C, while MMBZ5238B-TP maintains -55°C. Interchangeability depends on application temperature requirements.

Q: What does MSL 1 (Unlimited) mean for moisture sensitivity?

A: MSL 1 indicates unlimited shelf life without moisture control requirements. All listed parts carry this rating, eliminating moisture-related handling constraints during storage and assembly.

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