CMPZ5257B BK PBFREE Equivalent & Substitute Parts

Part Overview

The CMPZ5257B BK PBFREE is a 33 V Zener diode manufactured by Central Semiconductor Corp, rated for 350 mW power dissipation in a surface mount SOT-23 package. This component is classified as Active product status and is ROHS3 compliant. Equivalent and substitute parts are identified based on matching electrical specifications including nominal Zener voltage, power rating, tolerance, and mechanical package compatibility. Alternative sources are necessary to ensure supply chain continuity, optimize procurement costs, and maintain design flexibility across manufacturing partners.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	33	V
Power - Max	350	mW
Tolerance	±5%	-
Impedance (Max)	58	Ohms
Current - Reverse Leakage @ Vr	100	nA @ 25 V
Voltage - Forward (Vf) (Max) @ If	900	mV @ 10 mA
Operating Temperature	-65 to 150	°C
Mounting Type	Surface Mount	-
Package / Case	TO-236-3, SC-59, SOT-23-3	-
RoHS Status	ROHS3 Compliant	-

Substitute Part Grouping Explanation

Substitution of the CMPZ5257B BK PBFREE is determined by the following critical parameters:

Primary Matching Criteria:

Nominal Zener voltage: 33 V (exact match required)
Package type: SOT-23 or TO-236-3 (mechanical and electrical compatibility)
Operating temperature range: -65°C to 150°C minimum
RoHS3 compliance and REACH unaffected status

Secondary Compatibility Factors:

Power rating: 350 mW (primary part) to 225 mW minimum (acceptable for lower-power applications)
Tolerance: ±5% (primary part) to ±1% (tighter tolerance acceptable)
Impedance: 58 Ohms (primary part) to 80 Ohms (acceptable variation)
Reverse leakage current: 100 nA @ 25 V (primary part) to 50 nA (acceptable improvement)

Parts are grouped by power rating capability and tolerance specification. Parts with 350 mW or 300 mW ratings provide direct substitution. Parts with 250 mW or 225 mW ratings are suitable for applications with lower power dissipation requirements. Tolerance variations (±1%, ±2%, ±5%, ±6%) do not prevent substitution but should be evaluated against circuit design margins.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Power (mW)	Tolerance	Zzt (Ohms)	Ir @ Vr (nA)	Package	Temp Range (°C)
CMPZ5257B BK PBFREE	Central Semiconductor Corp	33	350	±5%	58	100 @ 25V	SOT-23	-65 to 150
BZX84-A33,215	NXP USA Inc.	33	250	±1%	80	50 @ 700mV	SOT-23	-65 to 150
BZX84-B33,215	Nexperia USA Inc.	33	250	±2%	80	50 @ 23.1V	TO-236AB	-65 to 150
BZX84-C33,215	NXP Semiconductors	33	250	±5%	80	50 @ 23.1V	TO-236AB	-65 to 150
BZX84-C33,235	Nexperia USA Inc.	33	250	±5%	80	50 @ 23.1V	TO-236AB	-65 to 150
BZX84C33-7-F	Diodes Incorporated	33	300	±6%	80	100 @ 23.1V	SOT-23-3	-65 to 150
BZX84C33-E3-08	Vishay General Semiconductor	33	300	±5%	80	50 @ 23.1V	SOT-23-3	-55 to 150
BZX84C33-TP	Micro Commercial Co	33	350	±5%	80	100 @ 23.1V	SOT-23	-55 to 150
MMBZ5257B-7-F	Diodes Incorporated	33	350	±5%	58	100 @ 25V	SOT-23-3	-65 to 150
MMBZ5257BLT1G	onsemi	33	225	±5%	58	100 @ 25V	SOT-23-3	-65 to 150
MMBZ5257BTS-7-F	Diodes Incorporated	33	200	±5%	58	100 @ 25V	SOT-363	-65 to 150

Engineering Selection Recommendations

Direct Substitutes (Highest Compatibility):

MMBZ5257B-7-F (Diodes Incorporated) provides direct substitution with identical electrical specifications: 33 V nominal voltage, 350 mW power rating, ±5% tolerance, 58 Ohms impedance, and -65°C to 150°C operating range. Package designation SOT-23-3 is mechanically equivalent to SOT-23. Both parts are ROHS3 compliant with unlimited moisture sensitivity level.

BZX84C33-TP (Micro Commercial Co) matches the primary part in voltage, power rating, and tolerance. Operating temperature range is -55°C to 150°C, which is acceptable for most applications but does not extend to -65°C. Impedance specification is 80 Ohms versus 58 Ohms in the primary part.

Secondary Substitutes (Acceptable with Design Verification):

BZX84C33-7-F (Diodes Incorporated) and BZX84C33-E3-08 (Vishay) provide 300 mW power rating, which is 86% of the primary part's 350 mW capacity. These parts are suitable for applications where power dissipation does not exceed 300 mW. Both maintain 33 V nominal voltage and ±5% or ±6% tolerance. Operating temperature range is -65°C to 150°C (BZX84C33-7-F) or -55°C to 150°C (BZX84C33-E3-08).

BZX84-A33,215, BZX84-B33,215, and BZX84-C33,215 (NXP/Nexperia) provide 250 mW power rating with tighter tolerance specifications (±1% to ±2%). These parts are suitable for lower-power applications and offer improved voltage accuracy. All maintain -65°C to 150°C operating range and ROHS3 compliance.

Lower-Power Alternative:

MMBZ5257BLT1G (onsemi) provides 225 mW power rating with identical impedance (58 Ohms) and reverse leakage characteristics. This part is suitable for applications with reduced power dissipation requirements and maintains full -65°C to 150°C operating range.

Array Configuration:

MMBZ5257BTS-7-F (Diodes Incorporated) is a 3-independent Zener diode array in SOT-363 package. This part is not a direct substitute for single-diode applications but provides equivalent electrical specifications per diode element (33 V, 200 mW per element, ±5% tolerance). Use only when circuit design requires multiple independent Zener elements.

All recommended substitutes maintain ROHS3 compliance, REACH unaffected status, and ECCN EAR99 classification.

Frequently Asked Questions (FAQ)

Q: Can BZX84-C33,215 replace CMPZ5257B BK PBFREE in all applications?

A: BZX84-C33,215 is electrically compatible for voltage regulation (33 V nominal, ±5% tolerance) but has reduced power rating (250 mW versus 350 mW). Substitution is valid only if circuit power dissipation does not exceed 250 mW. Verify thermal design margins before implementation.

Q: What is the difference between SOT-23 and SOT-23-3 packages?

A: SOT-23 and SOT-23-3 are equivalent designations for the same three-terminal surface mount package (TO-236-3, SC-59). Both terms refer to identical mechanical and electrical footprints. Parts specified as SOT-23 or SOT-23-3 are mechanically interchangeable.

Q: Is MMBZ5257BLT1G suitable for high-power applications?

A: No. MMBZ5257BLT1G is rated for 225 mW maximum power dissipation, which is 64% of the primary part's 350 mW rating. Use this part only in applications where power dissipation is confirmed to remain below 225 mW. For higher power requirements, select BZX84C33-7-F (300 mW), BZX84C33-TP (350 mW), or MMBZ5257B-7-F (350 mW).

Q: Why do some substitutes have ±1% or ±2% tolerance instead of ±5%?

A: Tighter tolerance specifications (±1%, ±2%) indicate improved manufacturing precision and voltage accuracy. These parts are acceptable substitutes for the ±5% primary part. Tighter tolerance does not create compatibility issues; it provides better voltage regulation performance.

Q: Can BZX84C33-E3-08 be used in applications requiring -65°C operation?

A: BZX84C33-E3-08 is specified for -55°C to 150°C operating range. It is not suitable for applications requiring operation below -55°C. For full -65°C to 150°C range compatibility, use MMBZ5257B-7-F, BZX84C33-7-F, or BZX84-A33,215.

Q: What is the significance of impedance (Zzt) differences between 58 Ohms and 80 Ohms?

A: Impedance affects voltage regulation stability under varying load conditions. The primary part specifies 58 Ohms; substitutes with 80 Ohms impedance have slightly higher dynamic resistance. This difference is acceptable for most applications but should be verified in circuits with stringent voltage regulation requirements.

Q: Is MMBZ5257BTS-7-F a direct replacement for single-diode applications?

A: No. MMBZ5257BTS-7-F is a three-independent Zener diode array in SOT-363 package. It is not mechanically compatible with SOT-23 footprints and is intended for applications requiring multiple independent Zener elements. Use only when circuit design specifically requires array configuration.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts are ROHS3 compliant and REACH unaffected. Compliance status is maintained across all recommended alternatives.

Q: What is the impact of reverse leakage current differences?

A: The primary part specifies 100 nA @ 25 V reverse leakage. Substitutes with 50 nA leakage (BZX84 series) represent improved performance with lower standby current. This difference is beneficial and does not create compatibility issues. Higher leakage specifications are not acceptable substitutes.

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