MMSZ5259B-7 Equivalent & Substitute Parts

Part Overview

The MMSZ5259B-7 is a 39 V, 500 mW Zener diode in SOD-123 surface mount packaging manufactured by Diodes Incorporated. This component is classified as discontinued at DiGi Electronics, with 1013 pieces available in current inventory. The part operates across a temperature range of -65°C to 150°C and maintains ±5% voltage tolerance. Due to its discontinued status, equivalent and substitute parts from active manufacturers are necessary for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	39	V
Power - Maximum	500	mW
Tolerance	±5	%
Impedance (Maximum)	80	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 30 V	nA
Voltage - Forward (Maximum) @ If	900 mV @ 10 mA	mV
Operating Temperature Range	-65 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOD-123	—
RoHS Status	RoHS non-compliant	—

Substitute Part Grouping Explanation

Substitution of the MMSZ5259B-7 is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 39 V nominal
Power dissipation: 500 mW maximum
Voltage tolerance: ±5%
Package type: SOD-123 surface mount
Operating temperature range: -65°C to 150°C minimum
Forward voltage: 900 mV maximum @ 10 mA

Secondary Compatibility Parameters:

Impedance (Zzt): Maximum 80 Ohms (allows higher values in certain applications)
Reverse leakage current: 100 nA @ 30 V (allows lower values)
Mounting type: Surface mount only

Substitute parts are grouped into two categories:

Full Parametric Equivalents: Parts matching all primary and secondary specifications, including impedance and reverse leakage characteristics identical to the main part.

Functional Equivalents: Parts meeting all primary substitution criteria with variations in secondary parameters (impedance, reverse leakage, or power dissipation) that remain within acceptable operational limits for the 39 V zener function.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Vz (V)	Power (mW)	Tolerance (%)	Zzt (Ohms)	Reverse Leakage @ Vr	Vf (Max) @ If	Temp Range (°C)	Package	Product Status	RoHS Status
MMSZ5259B-7	Diodes Incorporated	39	500	±5	80	100 nA @ 30 V	900 mV @ 10 mA	-65 to 150	SOD-123	Discontinued	Non-compliant
BZT52C39-7-F	Diodes Incorporated	39	500	±5	130	100 nA @ 27.3 V	900 mV @ 10 mA	-65 to 150	SOD-123	Active	ROHS3 Compliant
MMSZ5259B-7-F	Diodes Incorporated	39	500	±5	80	100 nA @ 30 V	900 mV @ 10 mA	-65 to 150	SOD-123	Active	ROHS3 Compliant
BZT52C39-TP	Micro Commercial Co	39	200	±5	130	100 nA @ 27.3 V	900 mV @ 10 mA	-65 to 150	SOD-123	Active	ROHS3 Compliant
BZT52H-C39,115	Nexperia USA Inc.	39	375	±5	75	50 nA @ 27.3 V	900 mV @ 10 mA	-65 to 150	SOD-123F	Active	ROHS3 Compliant
MMSZ5259BT1G	onsemi	39	500	±5	80	100 nA @ 30 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
SZMMSZ5259BT1G	onsemi	39	500	±5	80	100 nA @ 30 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
CMHZ5259B TR PBFREE	Central Semiconductor Corp	39	500	±5	80	100 nA @ 30 V	900 mV @ 10 mA	-65 to 150	SOD-123	Active	ROHS3 Compliant

Engineering Selection Recommendations

Full Parametric Equivalent (Recommended Primary Substitute):

MMSZ5259B-7-F from Diodes Incorporated is the direct parametric equivalent to the MMSZ5259B-7. This part maintains identical electrical specifications including 39 V zener voltage, 500 mW power rating, 80 Ohms maximum impedance, and 100 nA reverse leakage at 30 V. The primary distinction is product status: MMSZ5259B-7-F is active and ROHS3 compliant, addressing the discontinued status of the original part. Operating temperature range remains -65°C to 150°C. This substitution requires no circuit redesign.

Equivalent from Alternative Manufacturer (Recommended Secondary Substitute):

CMHZ5259B TR PBFREE from Central Semiconductor Corp provides full parametric equivalence with identical electrical characteristics and operating temperature range (-65°C to 150°C). This part is active and ROHS3 compliant. Selection of this substitute is appropriate when Diodes Incorporated parts are unavailable or when supply chain diversification is required.

Active Manufacturer Alternatives with Acceptable Variations:

MMSZ5259BT1G and SZMMSZ5259BT1G from onsemi are functionally equivalent with matching 39 V, 500 mW, and 80 Ohms specifications. Both parts are active and ROHS3 compliant. The operating temperature range is -55°C to 150°C, which is narrower at the lower end compared to the original -65°C specification. SZMMSZ5259BT1G includes AEC-Q101 automotive qualification. These substitutes are suitable for applications where the -55°C minimum temperature is acceptable.

Functional Substitute with Power Derating:

BZT52C39-TP from Micro Commercial Co operates at 39 V with ±5% tolerance but is rated for 200 mW maximum power dissipation, representing a 60% reduction from the original 500 mW specification. This part is active and ROHS3 compliant. Selection of this substitute requires verification that circuit power dissipation does not exceed 200 mW. Impedance is 130 Ohms, higher than the original 80 Ohms specification.

Functional Substitute with Package Variation:

BZT52H-C39,115 from Nexperia USA Inc. provides 39 V zener function with 375 mW power rating and is packaged in SOD-123F (variant of SOD-123). This part is active, ROHS3 compliant, and carries AEC-Q101 automotive qualification. Impedance is 75 Ohms (lower than original), and reverse leakage is 50 nA at 27.3 V (lower than original). The SOD-123F package may require PCB layout verification for compatibility with SOD-123 footprints.

Higher Impedance Substitute:

BZT52C39-7-F from Diodes Incorporated matches the 39 V, 500 mW, and ±5% tolerance specifications but specifies 130 Ohms maximum impedance compared to 80 Ohms in the original part. This part is active and ROHS3 compliant. Higher impedance may affect voltage regulation performance in applications with varying load conditions. Selection requires circuit analysis to confirm acceptable performance.

Frequently Asked Questions (FAQ)

Q: Can MMSZ5259B-7-F be used as a direct replacement for MMSZ5259B-7?

A: Yes. MMSZ5259B-7-F is a full parametric equivalent with identical electrical specifications (39 V, 500 mW, 80 Ohms impedance, 100 nA reverse leakage). The primary difference is that MMSZ5259B-7-F is active and ROHS3 compliant, whereas the original is discontinued and non-compliant. No circuit modifications are required.

Q: What is the difference between MMSZ5259BT1G and SZMMSZ5259BT1G?

A: Both parts from onsemi provide identical electrical specifications (39 V, 500 mW, 80 Ohms impedance). The primary difference is that SZMMSZ5259BT1G includes AEC-Q101 automotive qualification and has significantly higher inventory availability (125,400 pieces versus 6,908 pieces). Both have an operating temperature range of -55°C to 150°C, which is narrower at the lower end than the original -65°C specification.

Q: Why does BZT52C39-TP have lower power rating than the original part?

A: BZT52C39-TP is rated for 200 mW maximum power dissipation, compared to 500 mW for MMSZ5259B-7. This represents a different product variant within the 39 V zener family. Selection of this part requires verification that circuit power dissipation remains below 200 mW. If higher power dissipation is required, alternative substitutes with 500 mW ratings should be selected.

Q: Is the SOD-123F package used by BZT52H-C39,115 compatible with SOD-123 PCB footprints?

A: SOD-123F is a variant of the SOD-123 package. Physical compatibility depends on specific PCB footprint design. PCB layout verification is required before selecting BZT52H-C39,115 as a substitute. Consult the component datasheets and PCB design guidelines to confirm footprint compatibility.

Q: What does impedance (Zzt) mean, and why does it vary among substitutes?

A: Impedance (Zzt) is the dynamic impedance of the zener diode at the specified test current. Lower impedance indicates better voltage regulation performance under varying load conditions. The original MMSZ5259B-7 specifies 80 Ohms maximum impedance. Substitutes with higher impedance (such as BZT52C39-7-F at 130 Ohms) may exhibit slightly different voltage regulation characteristics. Circuit analysis is recommended for applications with stringent voltage regulation requirements.

Q: Can I use CMHZ5259B TR PBFREE if Diodes Incorporated parts are unavailable?

A: Yes. CMHZ5259B TR PBFREE from Central Semiconductor Corp is a full parametric equivalent with identical electrical specifications and operating temperature range (-65°C to 150°C). This part is active and ROHS3 compliant. Selection of this substitute is appropriate for supply chain diversification or when Diodes Incorporated inventory is depleted.

Q: What is the significance of AEC-Q101 qualification on SZMMSZ5259BT1G and BZT52H-C39,115?

A: AEC-Q101 is an automotive qualification standard that certifies component reliability for automotive applications. Parts carrying this qualification have undergone additional testing and screening. Selection of AEC-Q101 qualified parts is required for automotive designs or applications with equivalent reliability requirements.

Q: Does the narrower operating temperature range (-55°C to 150°C) of onsemi parts affect suitability?

A: The onsemi parts (MMSZ5259BT1G and SZMMSZ5259BT1G) specify -55°C to 150°C, compared to -65°C to 150°C for the original part. If the application requires operation below -55°C, these substitutes are not suitable. For applications with minimum operating temperatures above -55°C, these parts are fully acceptable.

Q: What is the difference between reverse leakage specifications at different voltages?

A: Reverse leakage current varies with applied reverse voltage. The original MMSZ5259B-7 specifies 100 nA at 30 V reverse voltage. Some substitutes specify reverse leakage at 27.3 V. Lower reverse leakage (such as 50 nA in BZT52H-C39,115) indicates better leakage performance. These variations are within normal manufacturing tolerances and do not affect functional compatibility in standard applications.

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