MMSZ5259ET1 Zener Diode 39V 500mW SOD-123 Equivalent & Substitute Parts

Part Overview

The MMSZ5259ET1 is a 39V 500mW Zener diode in SOD-123 surface mount package manufactured by onsemi. This component is classified as obsolete product status. The MMSZ5259ET1 has been superseded by active production alternatives that maintain identical electrical specifications and mechanical compatibility. Identifying equivalent and substitute parts is necessary to ensure design continuity, maintain supply chain reliability, and access components with active manufacturing status and current compliance certifications.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	39	V
Tolerance	±5	%
Power - Maximum	500	mW
Impedance (Maximum)	80	Ohms
Current - Reverse Leakage @ Vr	100	nA @ 30V
Voltage - Forward (Maximum) @ If	900	mV @ 10mA
Operating Temperature Range	-55 to 150	°C
Package / Case	SOD-123	—
Mounting Type	Surface Mount	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the MMSZ5259ET1 is determined by strict equivalence of the following electrical and mechanical parameters:

Critical Matching Parameters:

Voltage - Zener (Nominal): 39V
Tolerance: ±5%
Power - Maximum: 500mW
Impedance (Maximum): 80 Ohms
Current - Reverse Leakage @ Vr: 100nA @ 30V
Voltage - Forward (Maximum) @ If: 900mV @ 10mA
Operating Temperature Range: -55°C to 150°C
Package / Case: SOD-123
Mounting Type: Surface Mount

Substitute Categories:

Direct Manufacturer Equivalent: MMSZ5259BT1G (onsemi) — Active status replacement with identical specifications and RoHS3 compliance.

Parametric Equivalents: SZMMSZ5259BT1G (onsemi), MMSZ5259B-E3-08 (Vishay), MMSZ5259B-E3-18 (Vishay), MMSZ5259B-G3-08 (Vishay), MMSZ5259B-G3-18 (Vishay), MMSZ5259B-HE3-08 (Vishay), MMSZ5259B-TP (Micro Commercial Co) — All maintain identical electrical specifications and SOD-123 package compatibility.

Upgrade Alternative: MMSZ5259B-7-F (Diodes Incorporated) — Extends operating temperature range to -65°C and provides active product status with RoHS3 compliance.

Similar Alternative: BZT52H-C39,115 (Nexperia USA Inc.) — Maintains 39V nominal voltage and ±5% tolerance with SOD-123F package variant; power rating reduced to 375mW and impedance to 75 Ohms; includes automotive AEC-Q101 qualification.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance (%)	Power (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf @ If (mV)	Temp Range (°C)	Package	Status	RoHS
MMSZ5259ET1	onsemi	39	±5	500	80	100 @ 30V	900 @ 10mA	-55 to 150	SOD-123	Obsolete	Non-compliant
MMSZ5259BT1G	onsemi	39	±5	500	80	100 @ 30V	900 @ 10mA	-55 to 150	SOD-123	Active	RoHS3
SZMMSZ5259BT1G	onsemi	39	±5	500	80	100 @ 30V	900 @ 10mA	-55 to 150	SOD-123	Active	RoHS3
MMSZ5259B-7-F	Diodes Inc.	39	±5	500	80	100 @ 30V	900 @ 10mA	-65 to 150	SOD-123	Active	RoHS3
MMSZ5259B-E3-08	Vishay	39	±5	500	80	100 @ 30V	—	-55 to 150	SOD-123	Active	RoHS3
MMSZ5259B-E3-18	Vishay	39	±5	500	80	100 @ 30V	—	-55 to 150	SOD-123	Active	RoHS3
MMSZ5259B-G3-08	Vishay	39	±5	500	80	100 @ 30V	—	-55 to 150	SOD-123	Active	RoHS3
MMSZ5259B-G3-18	Vishay	39	±5	500	80	100 @ 30V	—	-55 to 150	SOD-123	Active	RoHS3
MMSZ5259B-HE3-08	Vishay	39	±5	500	80	100 @ 30V	—	-55 to 150	SOD-123	Obsolete	RoHS3
MMSZ5259B-TP	Micro Commercial	39	±5	500	80	100 @ 30V	900 @ 10mA	-55 to 150	SOD-123	Active	RoHS3
BZT52H-C39,115	Nexperia	39	±5	375	75	50 @ 27.3V	900 @ 10mA	-65 to 150	SOD-123F	Active	RoHS3

Engineering Selection Recommendations

Primary Recommendation: MMSZ5259BT1G (onsemi)

The MMSZ5259BT1G is the direct active-status replacement for the obsolete MMSZ5259ET1. This part maintains 100% electrical and mechanical compatibility with identical specifications across all critical parameters. The MMSZ5259BT1G carries RoHS3 compliance and active manufacturing status, ensuring long-term supply availability and regulatory alignment. Packaging is available in Cut Tape (CT) and Digi-Reel® formats.

Secondary Recommendation: SZMMSZ5259BT1G (onsemi, Automotive Grade)

The SZMMSZ5259BT1G provides identical electrical specifications with automotive-grade qualification (AEC-Q101) and active product status. This variant is suitable for applications requiring automotive-level reliability and traceability. Packaging is Tape & Reel (TR) format with significantly higher inventory availability (125,400 pcs).

Alternative Recommendation: MMSZ5259B-7-F (Diodes Incorporated)

The MMSZ5259B-7-F extends the operating temperature range to -65°C while maintaining all other electrical specifications. This upgrade option is applicable for designs requiring enhanced low-temperature performance. Active product status and RoHS3 compliance are confirmed.

Conditional Alternative: BZT52H-C39,115 (Nexperia USA Inc.)

The BZT52H-C39,115 maintains the 39V nominal voltage specification but operates at reduced power dissipation (375mW versus 500mW) and lower impedance (75 Ohms versus 80 Ohms). This part includes automotive AEC-Q101 qualification and extended temperature range (-65°C to 150°C). Selection of this alternative requires confirmation that the reduced power rating and impedance specifications are acceptable for the application circuit.

Frequently Asked Questions (FAQ)

Q1: Can MMSZ5259BT1G be used as a direct replacement for MMSZ5259ET1?

Yes. The MMSZ5259BT1G is electrically and mechanically identical to the MMSZ5259ET1 across all specified parameters: 39V nominal voltage, ±5% tolerance, 500mW power rating, 80 Ohms impedance, and SOD-123 package. The primary difference is product status (Active versus Obsolete) and RoHS3 compliance certification.

Q2: What is the difference between MMSZ5259BT1G and SZMMSZ5259BT1G?

Both parts share identical electrical specifications and SOD-123 packaging. The SZMMSZ5259BT1G is automotive-grade with AEC-Q101 qualification and carries the "SZ" prefix designation. SZMMSZ5259BT1G offers significantly higher inventory availability and is recommended for automotive applications or designs requiring automotive-level traceability.

Q3: Why would I select MMSZ5259B-7-F over MMSZ5259BT1G?

The MMSZ5259B-7-F extends the minimum operating temperature to -65°C compared to -55°C for MMSZ5259BT1G. Selection depends on application requirements. If the circuit operates in environments below -55°C, the MMSZ5259B-7-F is necessary. Otherwise, MMSZ5259BT1G is the preferred choice due to onsemi original manufacturer status.

Q4: Is BZT52H-C39,115 a suitable substitute?

The BZT52H-C39,115 maintains the 39V nominal voltage and ±5% tolerance but operates at reduced power dissipation (375mW versus 500mW) and lower impedance (75 Ohms versus 80 Ohms). This part is suitable only if the application circuit can operate within these reduced electrical parameters. The SOD-123F package is mechanically compatible with SOD-123 footprints. Automotive AEC-Q101 qualification is included.

Q5: What packaging options are available for substitute parts?

Substitute parts are available in multiple packaging formats: Cut Tape (CT) & Digi-Reel® (MMSZ5259BT1G, MMSZ5259B-HE3-08), Tape & Reel (TR) (SZMMSZ5259BT1G, MMSZ5259B-7-F, Vishay variants, MMSZ5259B-TP, BZT52H-C39,115). Selection depends on procurement volume and assembly process requirements.

Q6: Are all substitute parts RoHS3 compliant?

All active-status substitute parts listed carry RoHS3 compliance certification. The original MMSZ5259ET1 is RoHS non-compliant. The MMSZ5259B-HE3-08 is RoHS3 compliant but carries obsolete product status.

Q7: Which substitute offers the best long-term supply availability?

The SZMMSZ5259BT1G offers the highest inventory level (125,400 pcs) and active automotive-grade status, providing optimal long-term supply security. MMSZ5259BT1G (6,908 pcs) is the second choice for standard industrial applications.

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