MM5Z12VST1G Equivalent & Substitute Parts

Part Overview

The MM5Z12VST1G is a Zener diode rated at 12 V nominal with 500 mW power dissipation in a surface mount SOD-523 package, manufactured by onsemi. This component is classified as obsolete, indicating discontinuation from the manufacturer. Locating equivalent or substitute parts is necessary to support ongoing production, maintenance, and repair applications where this diode was originally specified.

Key Parameters

Parameter	Value
Voltage - Zener (Nom)	12 V
Power - Max	500 mW
Tolerance	±2%
Impedance (Max)	25 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 8 V
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA
Operating Temperature Range	-65°C ~ 150°C
Mounting Type	Surface Mount
Package / Case	SC-79, SOD-523
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the MM5Z12VST1G is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 12 V nominal
Package type: SOD-523 surface mount
Power rating: 500 mW or greater
Reverse leakage: 100 nA @ 8 V or lower
Operating temperature range: -65°C to 150°C minimum

Secondary Compatibility Factors:

Tolerance: ±2% preferred; wider tolerances acceptable if application permits
Impedance: 25 Ohms maximum preferred
Forward voltage: 900 mV @ 10 mA or lower

Substitute parts are grouped into two categories based on power rating alignment:

Category A - Full Power Rating Match (500 mW): Parts maintaining the original 500 mW specification provide direct functional equivalence with identical thermal performance.

Category B - Reduced Power Rating (150-350 mW): Parts with lower power dissipation ratings are suitable only for applications where the circuit operates below the original power envelope. These substitutes require verification that the actual operating power does not exceed the substitute part's rating.

Parameter Comparison

Parameter	MM5Z12VST1G	MM5Z12VT1G	BZT585B12T-7	CZRU12VB	EDZVFHT2R12B
Manufacturer	onsemi	onsemi	Diodes Incorporated	Comchip Technology	Rohm Semiconductor
Product Status	Obsolete	Active	Active	Active	Active
Voltage - Zener (Nom)	12 V	12 V	12 V	12 V	12 V
Tolerance	±2%	±5.4%	±2%	±3%	±2%
Power - Max	500 mW	500 mW	350 mW	150 mW	150 mW
Impedance (Max)	25 Ohms	25 Ohms	10 Ohms	22 Ohms	30 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 8 V	100 nA @ 8 V	100 nA @ 8 V	100 nA @ 9.1 V	100 nA @ 9 V
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	900 mV @ 10 mA	1.1 V @ 100 mA	900 mV @ 10 mA	Not Specified
Operating Temperature Range	-65°C ~ 150°C	-65°C ~ 150°C	-65°C ~ 150°C	-55°C ~ 125°C	-55°C ~ 150°C
Package / Case	SC-79, SOD-523	SC-79, SOD-523	SC-79, SOD-523	2-SMD, No Lead (0603)	SC-79, SOD-523
RoHS Status	Not Specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Packaging Type	Not Specified	Tape & Reel (TR)	Tape & Reel (TR)	Tape & Reel (TR)	Cut Tape (CT) & Digi-Reel®

Engineering Selection Recommendations

MM5Z12VT1G (onsemi)

This part is the primary substitute for MM5Z12VST1G. Both are onsemi products with identical 12 V, 500 mW specifications and SOD-523 packaging. MM5Z12VT1G carries Active product status with ROHS3 compliance. The tolerance specification differs at ±5.4% versus the original ±2%, which may impact applications requiring tighter voltage regulation. This substitute is suitable for direct replacement in designs where the wider tolerance is acceptable.

BZT585B12T-7 (Diodes Incorporated)

This part maintains 12 V nominal voltage and SOD-523 packaging with ±2% tolerance matching the original specification. Power rating is reduced to 350 mW, representing a 30% decrease from the original 500 mW. Impedance is improved at 10 Ohms versus 25 Ohms. This substitute is suitable only for applications where actual operating power remains below 350 mW. The part carries Active status and ROHS3 compliance.

EDZVFHT2R12B (Rohm Semiconductor)

This part provides 12 V nominal voltage with ±2% tolerance and 150 mW power rating in SOD-523 packaging. It carries automotive-grade qualification (AEC-Q101) and Active product status with ROHS3 compliance. Operating temperature range extends to 150°C maximum. This substitute is suitable only for low-power applications where operating power does not exceed 150 mW. The automotive qualification may provide additional reliability assurance for certain applications.

CZRU12VB (Comchip Technology)

This part provides 12 V nominal voltage with ±3% tolerance and 150 mW power rating. Package is 0603/SOD-523F (2-SMD, No Lead), which differs from the original SOD-523. Operating temperature range is limited to -55°C to 125°C, which is narrower than the original -65°C to 150°C specification. This substitute is suitable only for low-power applications and requires verification that the operating temperature range is compatible with the application. The different package footprint requires PCB layout modification.

Frequently Asked Questions (FAQ)

Q: Can MM5Z12VT1G be used as a direct replacement for MM5Z12VST1G?

A: Yes. Both parts share identical 12 V nominal voltage, 500 mW power rating, and SOD-523 packaging. The primary difference is tolerance specification (±5.4% versus ±2%) and product status (Active versus Obsolete). MM5Z12VT1G is suitable for direct replacement if the application tolerates the wider voltage tolerance.

Q: What is the key limitation when using BZT585B12T-7 as a substitute?

A: The power rating is reduced from 500 mW to 350 mW. This substitute is suitable only if the circuit operates at or below 350 mW. Applications requiring the full 500 mW dissipation capability must use MM5Z12VT1G or equivalent full-power alternatives.

Q: Why do CZRU12VB and EDZVFHT2R12B have lower power ratings?

A: These parts are designed for lower-power applications and use different thermal management approaches. CZRU12VB uses a 0603 package footprint, while EDZVFHT2R12B uses an EMD2 package. Both are limited to 150 mW maximum dissipation and are suitable only for circuits operating well below the original 500 mW specification.

Q: Is CZRU12VB compatible with the original PCB layout?

A: No. CZRU12VB uses a 0603 package (2-SMD, No Lead) while MM5Z12VST1G uses SOD-523 packaging. PCB footprint modification is required. The different package dimensions and lead configuration necessitate layout changes.

Q: Does operating temperature range affect substitute selection?

A: Yes. CZRU12VB is limited to -55°C to 125°C, which is narrower than the original -65°C to 150°C range. If the application requires operation below -55°C or above 125°C, CZRU12VB is not suitable. MM5Z12VT1G, BZT585B12T-7, and EDZVFHT2R12B all support the full -65°C to 150°C range.

Q: What does ROHS3 compliance indicate?

A: ROHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements, restricting lead and other hazardous materials. All active substitute parts listed carry ROHS3 compliance. The original MM5Z12VST1G does not specify RoHS status due to its obsolete classification.

Q: Can EDZVFHT2R12B be used in automotive applications?

A: EDZVFHT2R12B carries AEC-Q101 automotive qualification, indicating it meets automotive industry reliability and performance standards. This qualification is specific to this part and does not apply to other substitutes listed. Use EDZVFHT2R12B only if automotive-grade qualification is a requirement.

Q: What is the significance of impedance differences between substitutes?

A: Impedance affects voltage regulation under load changes. Lower impedance (BZT585B12T-7 at 10 Ohms) provides better voltage stability. Higher impedance (EDZVFHT2R12B at 30 Ohms) may result in greater voltage variation. For precision voltage regulation applications, lower impedance is preferred.

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