MMBZ5242B Zener Diode 12V 350mW SOT-23-3 Equivalent & Substitute Parts

Part Overview

The MMBZ5242B is a 12V Zener diode rated at 350mW in a surface mount SOT-23-3 package, manufactured by onsemi. This component is classified as obsolete, necessitating identification of equivalent and substitute parts for ongoing design requirements and procurement needs. The part maintains electrical specifications of ±5% voltage tolerance, 30 Ohms maximum impedance, and operates across a temperature range of -55°C to 150°C. Active equivalent parts from multiple manufacturers provide direct functional replacement with enhanced availability and current product status.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	12	V
Tolerance	±5%	-
Power - Max	350	mW
Impedance (Max)	30	Ohms
Current - Reverse Leakage @ Vr	1	µA @ 8.1V
Voltage - Forward (Vf) (Max) @ If	900	mV @ 10mA
Operating Temperature	-55 to 150	°C
Mounting Type	Surface Mount	-
Package / Case	SOT-23-3	-

Substitute Part Grouping Explanation

Substitution of the MMBZ5242B is determined by strict equivalence across the following critical parameters: nominal Zener voltage (12V), voltage tolerance (±5%), maximum power dissipation (350mW), impedance characteristics (30 Ohms maximum), forward voltage drop (900mV @ 10mA), and package configuration (SOT-23-3). Parts are grouped into three categories based on substitution relationship type:

Similar Parts (Lower Power Rating): MMBZ5242BLT1G, MMBZ5242ELT1G, and SZMMBZ5242BLT1G operate at reduced power ratings of 225mW while maintaining identical Zener voltage, tolerance, impedance, and forward voltage specifications. These parts are suitable for applications where the full 350mW dissipation is not required.

Direct Equivalents (Matching Specifications): BZX84C12-TP, CMPZ5242B BK PBFREE, CMPZ5242B TR PBFREE, MMBZ5242B-7-F, and MMBZ5242BQ-7-F provide full electrical equivalence at 350mW power rating with identical Zener voltage, tolerance, and package configuration across multiple manufacturers.

Similar Parts (Tighter Tolerance): BZX84B12-TP offers ±2% voltage tolerance versus the ±5% specification of the main part, with matching 350mW power rating and SOT-23-3 package.

Related Parts (Alternative Impedance): BZX84C12 TR PBFREE and BZX84B12-TP feature 25 Ohms maximum impedance compared to 30 Ohms, representing a tighter impedance specification while maintaining all other electrical parameters.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Vf @ 10mA (mV)	Temp Range (°C)	Package	Status
MMBZ5242B	onsemi	12	±5%	350	30	900	-55 to 150	SOT-23-3	Obsolete
MMBZ5242BLT1G	onsemi	12	±5%	225	30	900	-65 to 150	SOT-23-3	Active
MMBZ5242ELT1G	onsemi	12	±5%	225	30	900	-55 to 150	SOT-23-3	Active
SZMMBZ5242BLT1G	onsemi	12	±5%	225	30	900	-65 to 150	SOT-23-3	Active
BZX84C12-TP	Micro Commercial Co	12	±5%	350	25	900	-55 to 150	SOT-23	Active
CMPZ5242B BK PBFREE	Central Semiconductor	12	±5%	350	30	900	-65 to 150	SOT-23	Active
CMPZ5242B TR PBFREE	Central Semiconductor	12	±5%	350	30	900	-65 to 150	SOT-23	Active
MMBZ5242B-7-F	Diodes Incorporated	12	±5%	350	30	900	-65 to 150	SOT-23-3	Active
MMBZ5242BQ-7-F	Diodes Incorporated	12	±5%	350	30	900	-65 to 150	SOT-23-3	Active
BZX84B12-TP	Micro Commercial Co	12	±2%	350	25	900	-55 to 150	SOT-23	Active
BZX84C12 TR PBFREE	Central Semiconductor	12	±5%	350	25	900	-65 to 150	SOT-23	Active

Engineering Selection Recommendations

For Direct Replacement (Full 350mW Specification): Select MMBZ5242B-7-F or MMBZ5242BQ-7-F from Diodes Incorporated. Both parts maintain identical electrical specifications to the obsolete MMBZ5242B while offering active product status and RoHS3 compliance. MMBZ5242BQ-7-F includes AEC-Q101 automotive qualification for applications requiring automotive-grade components.

For Automotive Applications: SZMMBZ5242BLT1G (onsemi) and MMBZ5242BQ-7-F (Diodes Incorporated) both carry AEC-Q101 qualification. SZMMBZ5242BLT1G operates at 225mW, while MMBZ5242BQ-7-F maintains the full 350mW rating.

For Extended Temperature Range: MMBZ5242BLT1G, SZMMBZ5242BLT1G, CMPZ5242B variants, MMBZ5242B-7-F, and MMBZ5242BQ-7-F all support -65°C minimum operating temperature compared to -55°C for the original part.

For Reduced Power Dissipation Applications: MMBZ5242BLT1G or MMBZ5242ELT1G provide 225mW rating with identical Zener voltage and tolerance specifications. These parts reduce thermal load while maintaining functional equivalence for applications not requiring full 350mW dissipation.

For Tighter Impedance Specification: BZX84C12-TP or BZX84C12 TR PBFREE offer 25 Ohms maximum impedance versus 30 Ohms, providing improved voltage regulation characteristics.

For Tighter Voltage Tolerance: BZX84B12-TP provides ±2% tolerance versus ±5%, suitable for applications requiring enhanced voltage accuracy.

Frequently Asked Questions (FAQ)

Q: Can MMBZ5242BLT1G replace MMBZ5242B in all applications?

A: MMBZ5242BLT1G is electrically equivalent for Zener voltage, tolerance, impedance, and forward voltage specifications. The primary difference is reduced power rating (225mW versus 350mW). Substitution is valid only if the application power dissipation does not exceed 225mW. Extended temperature range (-65°C to 150°C) provides additional operational margin.

Q: What is the difference between MMBZ5242B-7-F and MMBZ5242BQ-7-F?

A: Both parts from Diodes Incorporated maintain identical electrical specifications (12V, ±5%, 350mW, SOT-23-3). MMBZ5242BQ-7-F includes AEC-Q101 automotive qualification and extended temperature range (-65°C to 150°C), while MMBZ5242B-7-F operates -65°C to 150°C without automotive qualification.

Q: Are BZX84C12-TP and CMPZ5242B TR PBFREE interchangeable with MMBZ5242B?

A: Both parts match the critical electrical specifications (12V Zener voltage, ±5% tolerance, 350mW power, 900mV forward voltage). BZX84C12-TP features 25 Ohms impedance versus 30 Ohms, representing a tighter specification. Both are electrically compatible substitutes with active product status.

Q: Why do some substitute parts have lower power ratings?

A: MMBZ5242BLT1G, MMBZ5242ELT1G, and SZMMBZ5242BLT1G are rated at 225mW instead of 350mW. These parts are suitable for applications where thermal dissipation is not a limiting factor. Selection depends on actual circuit power requirements.

Q: What packaging differences exist among substitute parts?

A: All parts use SOT-23-3 or equivalent TO-236-3 surface mount packages. Supplier device package designations may vary (SOT-23 versus SOT-23-3), but physical dimensions and pin configurations are identical for PCB compatibility.

Q: Which substitute part offers the best compliance profile?

A: MMBZ5242B-7-F, MMBZ5242BQ-7-F, CMPZ5242B variants, and BZX84C12 TR PBFREE all carry RoHS3 compliance. MMBZ5242BQ-7-F additionally includes AEC-Q101 automotive qualification for regulated applications.

Q: Can BZX84B12-TP be used where tighter voltage tolerance is required?

A: BZX84B12-TP provides ±2% voltage tolerance compared to ±5% for MMBZ5242B. This tighter tolerance is suitable for applications requiring enhanced voltage regulation accuracy. All other electrical parameters remain compatible.

Q: What is the inventory status for substitute parts?

A: MMBZ5242BLT1G (95,100 pcs), SZMMBZ5242BLT1G (17,100 pcs), BZX84C12-TP (43,634 pcs), CMPZ5242B TR PBFREE (25,544 pcs), and MMBZ5242B-7-F (22,554 pcs) offer substantial stock availability. MMBZ5242ELT1G (9,310 pcs) and MMBZ5242BQ-7-F (9,825 pcs) provide moderate availability.

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