MMSZ5256BT3 Equivalent & Substitute Parts

Part Overview

The MMSZ5256BT3 is a Zener diode rated at 30 V nominal voltage with 500 mW power dissipation in a surface mount SOD-123 package. Manufactured by onsemi, this component is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for new designs and ongoing production requirements. Substitute parts maintain identical or superior electrical characteristics while offering improved availability and compliance status.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	30	V
Tolerance	±5	%
Power - Max	500	mW
Impedance (Max)	49	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 23 V	nA
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	mV
Operating Temperature	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOD-123	—
RoHS Status	RoHS non-compliant	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitute parts are classified into three categories based on electrical and mechanical compatibility with the MMSZ5256BT3:

Direct Manufacturer Equivalents (onsemi): Parts MMSZ5256BT1G and MMSZ5256ET1G maintain all electrical parameters (30 V, 500 mW, ±5% tolerance, SOD-123 package) and are active products with RoHS3 compliance. These parts are interchangeable at the functional level.

Parametric Equivalents (onsemi Automotive Grade): Parts SMMSZ5256BT1G, SZMMSZ5256BT1G, and SZMMSZ5256ET1G meet all electrical specifications and package requirements. SMMSZ5256BT1G and SZMMSZ5256BT1G/SZMMSZ5256ET1G include AEC-Q101 automotive qualification. These parts provide enhanced reliability for automotive applications.

Cross-Manufacturer Equivalents: Parts from Diodes Incorporated (MMSZ5256B-7-F), Vishay (MMSZ5256B-E3-08), and Central Semiconductor (CMHZ5256B TR PBFREE) maintain the 30 V, 500 mW, ±5% tolerance specification in SOD-123 packaging with RoHS3 compliance and active product status.

Similar Parts (Reduced Power Rating): Parts BZT52H-C30,115 (NXP, 375 mW) and PZU30BA,115 (Nexperia, 320 mW) provide 30 V zener voltage with lower power ratings and different package options (SOD-123F and SOD-323 respectively). These are suitable only when power dissipation requirements are lower than 500 mW.

Substitution is determined by matching: Zener voltage (30 V), tolerance (±5%), power rating (500 mW minimum for direct equivalents), impedance (49 Ohms), reverse leakage (100 nA @ 23 V), forward voltage (900 mV @ 10 mA), operating temperature range (-55 to 150°C), and package type (SOD-123 for direct equivalents).

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance (%)	Power (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf @ If (mV)	Temp Range (°C)	Package	Status	RoHS
MMSZ5256BT3	onsemi	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Obsolete	Non-compliant
MMSZ5256BT1G	onsemi	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Active	RoHS3
MMSZ5256ET1G	onsemi	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Active	RoHS3
SMMSZ5256BT1G	onsemi	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Obsolete	RoHS3
SZMMSZ5256BT1G	onsemi	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Active	RoHS3
SZMMSZ5256ET1G	onsemi	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Active	RoHS3
MMSZ5256B-7-F	Diodes Incorporated	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-65 to 150	SOD-123	Active	RoHS3
MMSZ5256B-E3-08	Vishay	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-55 to 150	SOD-123	Active	RoHS3
CMHZ5256B TR PBFREE	Central Semiconductor	30	±5	500	49	100 @ 23 V	900 @ 10 mA	-65 to 150	SOD-123	Active	RoHS3
BZT52H-C30,115	NXP Semiconductors	30	±5	375	40	50 @ 21 V	900 @ 10 mA	-65 to 150	SOD-123F	Active	RoHS3
PZU30BA,115	Nexperia USA Inc.	30	±5	320	40	50 @ 23 V	1.1 @ 100 mA	-55 to 150	SOD-323	Active	RoHS3

Engineering Selection Recommendations

Primary Recommendation: MMSZ5256BT1G or MMSZ5256ET1G (onsemi) are the preferred direct substitutes. Both parts maintain complete electrical and mechanical compatibility with the MMSZ5256BT3, offer active product status with extended availability, and provide RoHS3 compliance. These parts are suitable for all applications where the original part was specified.

Automotive Applications: SZMMSZ5256BT1G or SZMMSZ5256ET1G (onsemi) are qualified to AEC-Q101 automotive standards and provide the same electrical specifications as the primary recommendation. These parts are appropriate for automotive-grade designs requiring enhanced reliability documentation.

Cross-Manufacturer Alternatives: MMSZ5256B-7-F (Diodes Incorporated), MMSZ5256B-E3-08 (Vishay), and CMHZ5256B TR PBFREE (Central Semiconductor) provide equivalent electrical performance with active product status and RoHS3 compliance. These options are suitable when supply chain diversification or preferred vendor requirements necessitate cross-manufacturer sourcing.

Extended Temperature Range: MMSZ5256B-7-F (Diodes Incorporated) and CMHZ5256B TR PBFREE (Central Semiconductor) extend the lower operating temperature limit to -65°C, providing enhanced performance in extreme cold environments compared to the original -55°C specification.

Reduced Power Applications: BZT52H-C30,115 (NXP) and PZU30BA,115 (Nexperia) are suitable only for applications where power dissipation does not exceed 375 mW and 320 mW respectively. These parts are not direct substitutes for the 500 mW rated MMSZ5256BT3 in high-power applications.

Frequently Asked Questions (FAQ)

Q: Can MMSZ5256BT1G directly replace MMSZ5256BT3 without circuit modification?

A: Yes. MMSZ5256BT1G maintains identical electrical parameters (30 V zener voltage, 500 mW power rating, ±5% tolerance, 49 Ohms impedance) and the same SOD-123 package. No circuit modifications are required for functional substitution.

Q: What is the difference between MMSZ5256BT1G and SZMMSZ5256BT1G?

A: Both parts meet identical electrical specifications and package requirements. SZMMSZ5256BT1G includes AEC-Q101 automotive qualification, making it suitable for automotive applications requiring enhanced reliability documentation. MMSZ5256BT1G is the standard industrial-grade equivalent.

Q: Why is the MMSZ5256BT3 marked as obsolete?

A: The MMSZ5256BT3 is obsolete due to its RoHS non-compliant status. Modern production has transitioned to RoHS3-compliant alternatives such as MMSZ5256BT1G and MMSZ5256ET1G, which provide equivalent performance with regulatory compliance.

Q: Can BZT52H-C30,115 replace MMSZ5256BT3 in all applications?

A: No. BZT52H-C30,115 has a reduced power rating of 375 mW compared to the 500 mW specification of MMSZ5256BT3. It is suitable only for applications where power dissipation does not exceed 375 mW. Additionally, it uses the SOD-123F package variant rather than SOD-123.

Q: What is the significance of the "T1G" suffix in MMSZ5256BT1G?

A: The "T1G" suffix indicates the part is supplied in Tape & Reel (TR) packaging format with the latest generation designation. This is a standard onsemi packaging designation for surface mount components.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended substitute parts (MMSZ5256BT1G, MMSZ5256ET1G, SZMMSZ5256BT1G, SZMMSZ5256ET1G, MMSZ5256B-7-F, MMSZ5256B-E3-08, CMHZ5256B TR PBFREE, BZT52H-C30,115, and PZU30BA,115) are RoHS3 compliant. The original MMSZ5256BT3 is RoHS non-compliant.

Q: Can I use MMSZ5256B-E3-08 from Vishay as a substitute?

A: Yes. MMSZ5256B-E3-08 maintains all critical electrical parameters (30 V, 500 mW, ±5% tolerance, 49 Ohms impedance) and uses the SOD-123 package. It is an active product with RoHS3 compliance and is suitable for direct substitution.

Q: What is the difference between SOD-123 and SOD-123F packages?

A: SOD-123F is a variant of the SOD-123 package with different dimensional specifications. While both are surface mount packages for small signal diodes, they have different footprints. BZT52H-C30,115 uses SOD-123F and may require PCB layout modifications if the original design specifies SOD-123.

Q: Is SMMSZ5256BT1G a suitable replacement despite being marked obsolete?

A: SMMSZ5256BT1G meets all electrical specifications and is RoHS3 compliant. However, it is marked as obsolete, which may limit future availability. MMSZ5256BT1G or MMSZ5256ET1G are preferred alternatives due to their active product status.

Q: Do all substitute parts have the same operating temperature range?

A: Most substitute parts operate from -55°C to 150°C, matching the original MMSZ5256BT3. However, MMSZ5256B-7-F (Diodes Incorporated) and CMHZ5256B TR PBFREE (Central Semiconductor) extend the lower limit to -65°C, providing enhanced cold-temperature performance.

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