MMBZ5255B Equivalent & Substitute Parts

Part Overview

The MMBZ5255B is a 28 V Zener diode rated for 350 mW maximum power dissipation in a surface mount 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 components maintain the core electrical specifications while offering improved availability and active product support.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	28	V
Tolerance	±5	%
Power - Maximum	350	mW
Impedance (Maximum)	44	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 21 V	nA
Voltage - Forward (Maximum) @ If	900 mV @ 10 mA	mV
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—

Substitute Part Grouping Explanation

Substitution eligibility for the MMBZ5255B is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 28 V nominal
Tolerance: ±5%
Impedance (Maximum): 44 Ohms
Current - Reverse Leakage @ Vr: 100 nA @ 21 V
Voltage - Forward (Maximum) @ If: 900 mV @ 10 mA
Mounting Type: Surface Mount
Package / Case: TO-236-3, SC-59, SOT-23-3

Secondary Consideration:

Power - Maximum: Substitute parts with equal or greater power rating are functionally compatible
Operating Temperature Range: Substitute parts with equal or extended temperature range are compatible

All substitute parts listed maintain identical zener voltage, tolerance, impedance, reverse leakage current, and forward voltage specifications. Variations in maximum power rating and operating temperature range do not preclude substitution when the application requirements are met.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance (%)	Power Max (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf Max @ If (mV)	Temp Range (°C)	Package	Status
MMBZ5255B	onsemi	28	±5	350	44	100 @ 21 V	900 @ 10 mA	-55 to 150	SOT-23-3	Obsolete
MMBZ5255BLT1G	onsemi	28	±5	225	44	100 @ 21 V	900 @ 10 mA	-65 to 150	SOT-23-3	Active
CMPZ5255B TR PBFREE	Central Semiconductor Corp	28	±5	350	44	100 @ 21 V	900 @ 10 mA	-65 to 150	SOT-23-3	Active
CZRT5255B-G	Comchip Technology	28	±5	300	44	100 @ 21 V	900 @ 10 mA	-65 to 150	SOT-23-3	Active
CZRT5255B-HF	Comchip Technology	28	±5	300	44	100 @ 21 V	900 @ 10 mA	-65 to 150	SOT-23-3	Active
MMBZ5255B-TP	Micro Commercial Co	28	±5	350	44	100 @ 21 V	900 @ 10 mA	-55 to 150	SOT-23-3	Active
MMBZ5255B_R1_00001	Panjit International Inc.	28	±5	410	44	100 @ 21 V	—	-55 to 150	SOT-23-3	Active

Engineering Selection Recommendations

Direct Replacement (Identical Specifications):

CMPZ5255B TR PBFREE and MMBZ5255B-TP are direct replacements for the MMBZ5255B. Both maintain 350 mW power rating, 28 V zener voltage, and all electrical parameters. CMPZ5255B TR PBFREE offers extended operating temperature range (-65°C to 150°C) and active product status with RoHS3 compliance. MMBZ5255B-TP maintains the original temperature range (-55°C to 150°C) and is actively manufactured by Micro Commercial Co with RoHS3 compliance.

Compatible Substitutes (Reduced Power Rating):

CZRT5255B-G and CZRT5255B-HF are functionally compatible substitutes with 300 mW power rating. These components maintain all critical electrical parameters and offer extended operating temperature range (-65°C to 150°C). Selection is appropriate for applications where 300 mW power dissipation meets design requirements.

Compatible Substitute (Reduced Power Rating, Extended Temperature):

MMBZ5255BLT1G is a compatible substitute with 225 mW power rating and extended operating temperature range (-65°C to 150°C). This component is actively manufactured by onsemi and RoHS3 compliant. Selection is appropriate for applications with lower power dissipation requirements.

Higher Power Rating Option:

MMBZ5255B_R1_00001 provides 410 mW power rating, exceeding the original specification. This component is actively manufactured by Panjit International Inc. with RoHS3 compliance and maintains the original temperature range (-55°C to 150°C).

All substitute parts are RoHS3 compliant and REACH unaffected. Selection should be based on application power dissipation requirements and temperature operating range.

Frequently Asked Questions (FAQ)

Q: Can MMBZ5255BLT1G replace MMBZ5255B in all applications?

A: MMBZ5255BLT1G is compatible when application power dissipation does not exceed 225 mW. The component maintains identical zener voltage (28 V), tolerance (±5%), impedance (44 Ohms), and reverse leakage specifications. Extended operating temperature range (-65°C to 150°C) provides additional margin. Applications requiring 350 mW dissipation require alternative substitutes.

Q: What is the difference between CZRT5255B-G and CZRT5255B-HF?

A: Both components are manufactured by Comchip Technology and maintain identical electrical specifications: 28 V zener voltage, ±5% tolerance, 300 mW power rating, 44 Ohms impedance, and -65°C to 150°C operating temperature range. The designations reflect different manufacturing or packaging variants. Both are functionally equivalent for circuit applications.

Q: Is MMBZ5255B_R1_00001 a direct replacement?

A: MMBZ5255B_R1_00001 is functionally compatible with higher power capability (410 mW versus 350 mW). All critical electrical parameters are maintained: 28 V zener voltage, ±5% tolerance, 44 Ohms impedance, and 100 nA reverse leakage. The higher power rating does not create incompatibility; it provides additional thermal margin. Operating temperature range matches the original (-55°C to 150°C).

Q: Why do substitute parts have different power ratings?

A: Power rating variation reflects different die sizes and thermal designs within the same SOT-23-3 package. All substitute parts maintain identical zener voltage, tolerance, impedance, and leakage specifications. Power rating selection depends on application thermal requirements. Higher power ratings provide additional dissipation capability without affecting electrical performance.

Q: Are all substitute parts RoHS3 compliant?

A: All listed substitute parts are RoHS3 compliant and REACH unaffected. The original MMBZ5255B is classified as obsolete; all active substitutes meet current environmental compliance requirements.

Q: Can CMPZ5255B TR PBFREE be used in designs requiring -55°C minimum temperature?

A: CMPZ5255B TR PBFREE operates from -65°C to 150°C, which exceeds the -55°C to 150°C range of the original MMBZ5255B. The extended lower temperature limit provides additional operational margin and is compatible with designs requiring -55°C minimum temperature.

Q: What packaging formats are available for substitutes?

A: Substitute parts are available in Tape & Reel (TR) and Cut Tape (CT) & Digi-Reel® packaging formats. All maintain SOT-23-3 package configuration. Packaging selection depends on production volume and assembly requirements. Electrical specifications remain identical across packaging variants.

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