MMBZ5250B Equivalent & Substitute Parts

Part Overview

The MMBZ5250B is a 20 V Zener diode rated at 350 mW in a surface mount SOT-23-3 package manufactured by onsemi. This component is classified as obsolete, indicating that direct procurement from the original manufacturer may be limited or unavailable. Equivalent and substitute parts are necessary to maintain design continuity, ensure supply chain reliability, and support ongoing production requirements for applications utilizing this Zener diode specification.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	20	V
Tolerance	±5%	—
Power - Maximum	350	mW
Impedance (Maximum)	25	Ohms
Current - Reverse Leakage @ Vr	100	nA @ 15 V
Voltage - Forward (Maximum) @ If	900	mV @ 10 mA
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the MMBZ5250B is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Zener voltage: 20 V nominal
Package / Case: TO-236-3, SC-59, or SOT-23-3 (surface mount)
Mounting Type: Surface Mount
Moisture Sensitivity Level: 1 (Unlimited)

Secondary Compatibility Parameters:

Power rating: 350 mW or greater
Impedance (Maximum): 25 Ohms or lower (lower impedance provides equivalent or superior performance)
Reverse leakage current: 100 nA @ 15 V or lower
Forward voltage: 900 mV @ 10 mA or lower
Operating temperature range: Must encompass -55°C to 150°C minimum

Tolerance Consideration:

Zener voltage tolerance of ±5% or tighter is acceptable for direct substitution

Substitute parts are grouped based on whether they meet all primary criteria and maintain compatibility within the secondary parameters. Parts with lower impedance, lower leakage current, or tighter tolerance provide equivalent or enhanced performance characteristics.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf @ If (mV)	Temp Range (°C)	Product Status
MMBZ5250B	onsemi	20	±5%	350	25	100 @ 15V	900 @ 10mA	-55 to 150	Obsolete
MMBZ5250BLT1G	onsemi	20	±5%	225	25	100 @ 15V	900 @ 10mA	-65 to 150	Active
SZMMBZ5250BLT1G	onsemi	20	±5%	225	25	100 @ 15V	900 @ 10mA	-65 to 150	Active
BZX84-A20,215	NXP Semiconductors	20	±1%	250	55	50 @ 14V	900 @ 10mA	-65 to 150	Active
BZX84B20-7-F	Diodes Incorporated	20	±2%	300	55	100 @ 14V	900 @ 10mA	-65 to 150	Active
BZX84B20-TP	Micro Commercial Co	20	±2%	350	55	100 @ 14V	900 @ 10mA	-55 to 150	Active
BZX84C20 TR	Central Semiconductor Corp	20	±5%	350	55	50 @ 14V	900 @ 10mA	-65 to 150	Active
BZX84C20-TP	Micro Commercial Co	20	±5%	350	55	100 @ 14V	900 @ 10mA	-55 to 150	Active
CMPZ5250B TR PBFREE	Central Semiconductor Corp	20	±5%	350	25	100 @ 15V	900 @ 10mA	-65 to 150	Active
CZRT55C20-G	Comchip Technology	20	±6%	350	55	100 @ 14V	900 @ 10mA	-65 to 150	Active
DDZX20C-7	Diodes Incorporated	20	±2.48%	300	28	50 @ 15V	900 @ 10mA	-65 to 150	Active

Engineering Selection Recommendations

Direct Substitutes (Highest Compatibility):

CMPZ5250B TR PBFREE (Central Semiconductor Corp) provides the closest electrical match to the MMBZ5250B. This part maintains identical impedance (25 Ohms), identical reverse leakage specification (100 nA @ 15 V), and identical power rating (350 mW). The part is RoHS3 compliant and active in production, ensuring supply availability. Operating temperature range extends to -65°C, providing enhanced low-temperature performance.

MMBZ5250BLT1G and SZMMBZ5250BLT1G (onsemi) are active production alternatives from the original manufacturer. Both maintain the same impedance (25 Ohms) and electrical characteristics as the obsolete MMBZ5250B. SZMMBZ5250BLT1G includes automotive qualification (AEC-Q101), suitable for applications requiring automotive-grade components. Power rating is reduced to 225 mW; this substitution is appropriate only when circuit design permits lower power dissipation.

Secondary Substitutes (Acceptable with Parameter Variance):

BZX84B20-TP (Micro Commercial Co) matches the 350 mW power rating and operating temperature range of the original part. Impedance increases to 55 Ohms, which may affect circuit performance in applications sensitive to dynamic impedance characteristics. This part is suitable for general-purpose applications where impedance variance is tolerable.

BZX84C20 TR (Central Semiconductor Corp) and BZX84C20-TP (Micro Commercial Co) provide 350 mW power rating with extended temperature range to -65°C. Impedance of 55 Ohms represents a trade-off in performance. Both parts are RoHS3 compliant and active in production.

BZX84-A20,215 (NXP Semiconductors) offers superior voltage tolerance (±1%) and lower reverse leakage (50 nA @ 14 V), providing enhanced precision. Power rating of 250 mW is lower than the original specification; this part is suitable only for applications with reduced power dissipation requirements. Automotive qualification (AEC-Q101) is available.

DDZX20C-7 (Diodes Incorporated) provides automotive qualification (AEC-Q101) with ±2.48% tolerance and 300 mW power rating. Impedance of 28 Ohms is closer to the original specification than most alternatives. This part is suitable for automotive applications requiring precision voltage regulation.

Substitutes with Limitations:

MMBZ5250BLT1G and SZMMBZ5250BLT1G are limited to 225 mW power rating. These parts are appropriate only when circuit design accommodates reduced power dissipation or when thermal management is not a constraint.

BZX84B20-7-F (Diodes Incorporated) and CZRT55C20-G (Comchip Technology) provide 300 mW and 350 mW ratings respectively, with impedance of 55 Ohms. These parts are suitable for general-purpose applications where impedance variance is acceptable.

Frequently Asked Questions (FAQ)

Q: Can MMBZ5250BLT1G replace MMBZ5250B in all applications?

A: MMBZ5250BLT1G is electrically compatible with MMBZ5250B for most applications. The primary difference is reduced power rating (225 mW versus 350 mW). Substitution is valid only when circuit design permits lower power dissipation. Impedance, voltage tolerance, and forward voltage characteristics are identical. Operating temperature range is extended to -65°C, providing enhanced performance at low temperatures.

Q: What is the significance of impedance (Zzt) in Zener diode substitution?

A: Impedance affects the dynamic voltage regulation characteristics of the Zener diode. Lower impedance (25 Ohms) provides better voltage stability under varying load conditions. The MMBZ5250B specifies 25 Ohms impedance. Substitute parts with 55 Ohms impedance will exhibit greater voltage variation with load changes. For applications requiring precise voltage regulation, select substitutes with impedance of 25 Ohms or lower, such as CMPZ5250B TR PBFREE or DDZX20C-7.

Q: Are all substitute parts RoHS3 compliant?

A: Most substitute parts listed are RoHS3 compliant. BZX84B20-TP (Micro Commercial Co) does not specify RoHS status in the provided data. Verify RoHS compliance with the component supplier if regulatory compliance is required for your application.

Q: What is the difference between MMBZ5250BLT1G and SZMMBZ5250BLT1G?

A: Both parts are manufactured by onsemi with identical electrical specifications. SZMMBZ5250BLT1G includes automotive qualification (AEC-Q101) and is designated for automotive applications. MMBZ5250BLT1G is suitable for general industrial and commercial applications. Select SZMMBZ5250BLT1G when automotive-grade qualification is required.

Q: Can I substitute a part with lower power rating if my circuit uses less power?

A: Yes, substitution with lower power rating is acceptable only when the actual power dissipation in your circuit is confirmed to be below the substitute part's rating. For example, MMBZ5250BLT1G (225 mW) can replace MMBZ5250B (350 mW) only if circuit analysis confirms power dissipation does not exceed 225 mW. Exceeding the power rating will cause component failure.

Q: What packaging options are available for these substitutes?

A: All substitute parts use the same surface mount package: TO-236-3, SC-59, or SOT-23-3. Packaging variations exist in tape format (Cut Tape, Tape & Reel, or Bulk), which affects procurement and handling but not electrical performance. Verify packaging format compatibility with your assembly process.

Q: Is CMPZ5250B TR PBFREE the best substitute for MMBZ5250B?

A: CMPZ5250B TR PBFREE provides the closest electrical match, maintaining identical impedance (25 Ohms), power rating (350 mW), and reverse leakage characteristics. The part is active in production, RoHS3 compliant, and offers extended temperature range to -65°C. This part is the preferred substitute when electrical performance equivalence is the primary requirement.

Q: What does "Moisture Sensitivity Level 1 (Unlimited)" mean?

A: Moisture Sensitivity Level 1 indicates the component has unlimited shelf life and requires no special moisture control during storage or handling. All substitute parts listed maintain MSL 1 classification, ensuring compatibility with standard component storage and assembly processes.

Q: Can I use BZX84-A20,215 as a direct replacement?

A: BZX84-A20,215 is electrically compatible but with important differences. This part offers superior voltage tolerance (±1% versus ±5%) and lower reverse leakage (50 nA @ 14 V versus 100 nA @ 15 V), providing enhanced precision. However, power rating is reduced to 250 mW, and impedance increases to 55 Ohms. Substitution is appropriate only when reduced power dissipation is acceptable and enhanced voltage precision is beneficial.

Q: Are automotive-qualified alternatives available?

A: Yes. SZMMBZ5250BLT1G (onsemi), BZX84-A20,215 (NXP Semiconductors), and DDZX20C-7 (Diodes Incorporated) all include AEC-Q101 automotive qualification. Select these parts when automotive-grade certification is required for your application.

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