BZX84C18 Equivalent & Substitute Parts

Part Overview

The BZX84C18 is a surface mount Zener diode rated at 18 V nominal with 350 mW maximum power dissipation in a SOT-23-3 package. Manufactured by onsemi, this component is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active manufacturers are necessary for new designs and ongoing production requirements. Substitute components maintain the core electrical specifications while offering improved availability and compliance with current regulatory standards.

Key Parameters

Parameter	BZX84C18 Value	Unit
Voltage - Zener (Nom)	18	V
Tolerance	±6%	—
Power - Max	350	mW
Impedance (Max)	45	Ohms
Current - Reverse Leakage @ Vr	50	nA @ 12.6 V
Voltage - Forward (Vf) (Max) @ If	900	mV @ 10 mA
Operating Temperature	-55°C ~ 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 BZX84C18 is determined by strict adherence to the following electrical and mechanical parameters:

Critical Parameters for Substitution:

Voltage - Zener (Nom): 18 V (exact match required)
Package / Case: TO-236-3, SC-59, SOT-23-3 (physical compatibility)
Mounting Type: Surface Mount (assembly compatibility)
Power - Max: 250 mW or greater (functional capability)
Impedance (Max): 45 Ohms or less (electrical performance)
Operating Temperature Range: Must encompass or exceed -55°C ~ 150°C
Voltage - Forward (Vf) (Max) @ If: 900 mV @ 10 mA (forward bias characteristics)

Substitute parts are grouped into two categories:

Direct Electrical Equivalents: Parts with identical or superior electrical specifications and active product status, including BZX84C18LT1G, BZX84C18LT3G, BZX84-C18,215, BZX84-C18,235, BZX84C18-7-F, and BZX84C18-TP.

Parametric Equivalents: Parts meeting all critical electrical parameters with minor variations in tolerance, impedance, or reverse leakage current, including BZX84B18-TP, BZX84C18_R1_00001, MMBZ5248B-7-F, and MMBZ5248BQ-7-F.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power Max (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf Max (mV)	Temp Range (°C)	Status	RoHS
BZX84C18	onsemi	18	±6%	350	45	50 @ 12.6V	900 @ 10mA	-55 ~ 150	Obsolete	—
BZX84C18LT1G	onsemi	18	±6%	225	45	50 @ 12.6V	900 @ 10mA	-65 ~ 150	Active	ROHS3
BZX84C18LT3G	onsemi	18	±6%	225	45	50 @ 12.6V	900 @ 10mA	-65 ~ 150	Active	ROHS3
BZX84-C18,215	NXP USA Inc.	18	±5%	250	45	50 @ 12.6V	900 @ 10mA	-65 ~ 150	Active	—
BZX84-C18,235	NXP Semiconductors	18	±5%	250	45	50 @ 12.6V	900 @ 10mA	-65 ~ 150	Active	—
BZX84B18-TP	Micro Commercial Co	18	±2%	350	45	100 @ 12.6V	900 @ 10mA	-55 ~ 150	Active	ROHS3
BZX84C18-7-F	Diodes Incorporated	18	±6%	300	45	100 @ 12.6V	900 @ 10mA	-65 ~ 150	Active	ROHS3
BZX84C18_R1_00001	Panjit International Inc.	18	±5%	410	45	100 @ 12.6V	—	-55 ~ 150	Active	ROHS3
MMBZ5248B-7-F	Diodes Incorporated	18	±5%	350	21	100 @ 14V	900 @ 10mA	-65 ~ 150	Active	ROHS3
MMBZ5248BQ-7-F	Diodes Incorporated	18	±5%	350	21	100 @ 14V	900 @ 10mA	-65 ~ 150	Active	ROHS3
BZX84C18-TP	Micro Commercial Co	18	±5%	350	45	100 @ 12.6V	900 @ 10mA	-55 ~ 150	Active	ROHS3

Engineering Selection Recommendations

For Direct Replacement with Extended Temperature Range: BZX84C18LT1G and BZX84C18LT3G from onsemi provide active product status with extended lower operating temperature limit (-65°C versus -55°C). Both maintain identical electrical specifications to the original BZX84C18 and carry ROHS3 compliance. These parts are recommended for applications requiring the same manufacturer lineage with improved regulatory compliance.

For Automotive and Qualified Applications: BZX84-C18,215 and BZX84-C18,235 from NXP Semiconductors are AEC-Q101 qualified automotive-grade components. These parts maintain the 18 V nominal specification with ±5% tolerance and extended temperature range (-65°C ~ 150°C). Selection of these parts is appropriate for automotive and mission-critical applications requiring formal qualification documentation.

For Higher Power Dissipation Requirements: BZX84C18_R1_00001 from Panjit International Inc. offers 410 mW maximum power dissipation, exceeding the original 350 mW specification. This part is suitable for applications where thermal margin is required. ROHS3 compliance and active status support long-term availability.

For Lower Impedance Performance: MMBZ5248B-7-F and MMBZ5248BQ-7-F from Diodes Incorporated feature reduced impedance (21 Ohms versus 45 Ohms), providing superior dynamic response characteristics. MMBZ5248BQ-7-F includes AEC-Q101 automotive qualification. These parts are appropriate for precision voltage regulation applications requiring tighter impedance control.

For Tighter Tolerance Requirements: BZX84B18-TP from Micro Commercial Co provides ±2% tolerance compared to the original ±6%, delivering improved voltage accuracy. Active status and ROHS3 compliance support modern supply chain requirements.

Frequently Asked Questions (FAQ)

Q: Can BZX84C18LT1G and BZX84C18LT3G be used as direct replacements for the obsolete BZX84C18?

A: Yes. Both parts maintain identical nominal Zener voltage (18 V), tolerance (±6%), impedance (45 Ohms), and forward voltage characteristics. The primary differences are reduced maximum power (225 mW versus 350 mW) and extended lower operating temperature (-65°C versus -55°C). Applications operating within 225 mW power dissipation limits experience no functional change. Both parts are active products with ROHS3 compliance.

Q: What is the difference between BZX84-C18,215 and BZX84-C18,235?

A: Both are NXP Semiconductors 18 V Zener diodes with identical electrical specifications (±5% tolerance, 250 mW power, 45 Ohms impedance, -65°C ~ 150°C operating range). The primary distinction is packaging designation: BZX84-C18,215 is specified as SOT-23, while BZX84-C18,235 is designated TO-236AB. Both are physically compatible with SOT-23-3 footprints and carry AEC-Q101 automotive qualification.

Q: Why do MMBZ5248B-7-F and MMBZ5248BQ-7-F have lower impedance (21 Ohms) than the original BZX84C18 (45 Ohms)?

A: Lower impedance indicates superior dynamic impedance performance, resulting in tighter voltage regulation under load transients. This is a performance enhancement rather than a limitation. Both parts maintain the 18 V nominal specification and 350 mW power rating. MMBZ5248BQ-7-F includes AEC-Q101 automotive qualification, making it suitable for precision regulation applications.

Q: Are all substitute parts ROHS3 compliant?

A: Most active substitute parts carry ROHS3 compliance. BZX84-C18,215 and BZX84-C18,235 from NXP do not specify ROHS3 status in the provided data. For applications requiring mandatory ROHS3 compliance, select from BZX84C18LT1G, BZX84C18LT3G, BZX84B18-TP, BZX84C18-7-F, BZX84C18_R1_00001, MMBZ5248B-7-F, MMBZ5248BQ-7-F, or BZX84C18-TP.

Q: Can BZX84C18_R1_00001 be used in applications designed for 350 mW maximum power?

A: Yes. BZX84C18_R1_00001 is rated for 410 mW maximum power dissipation, exceeding the 350 mW requirement. This part provides additional thermal margin and is suitable for applications with the same or lower power requirements. All other electrical specifications (18 V nominal, ±5% tolerance, 45 Ohms impedance, -55°C ~ 150°C operating range) are compatible.

Q: What is the significance of the different packaging designations (SOT-23, SOT-23-3, TO-236-3, SC-59)?

A: These designations refer to the same physical package with minor nomenclature variations across manufacturers and standards bodies. All substitute parts listed are compatible with SOT-23-3 footprints. Verify PCB footprint compatibility with the specific supplier device package designation during layout design.

Q: Which substitute part offers the best combination of availability, compliance, and performance?

A: BZX84C18-7-F from Diodes Incorporated combines high inventory availability (104,300 pcs), active product status, ROHS3 compliance, AEC-Q101 automotive qualification, extended temperature range (-65°C ~ 150°C), and 300 mW power rating. This part is suitable for both commercial and automotive applications requiring regulatory compliance and long-term supply assurance.

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