BZX84C18_D87Z Equivalent & Substitute Parts

Part Overview

The BZX84C18_D87Z is an 18 V Zener diode rated for 350 mW power dissipation 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 is no longer available. Identifying equivalent and substitute parts is 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)	18	V
Tolerance	±6%	—
Power - Maximum	350	mW
Impedance (Maximum)	45	Ohms
Current - Reverse Leakage @ Vr	50	nA @ 12.6 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	—

Substitute Part Grouping Explanation

Substitution of the BZX84C18_D87Z is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 18 V nominal
Package type: SOT-23-3 (TO-236-3, SC-59)
Mounting type: Surface Mount
Voltage tolerance: ±6% or tighter
Power rating: 350 mW or greater
Impedance: 45 Ohms or lower
Reverse leakage current: 50 nA @ 12.6 V or lower
Forward voltage: 900 mV @ 10 mA or lower
Operating temperature range: Must encompass -55°C to 150°C minimum

Substitute parts are grouped into two categories:

Direct Equivalents (Active Status): Parts meeting all primary criteria with active product status, ensuring ongoing availability and manufacturing support.

Parametric Equivalents (Active Status): Parts meeting core electrical specifications with minor variations in secondary parameters such as tolerance grade, impedance, or reverse leakage current, while maintaining functional compatibility within the application envelope.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf @ If (mV)	Temp Range (°C)	Status
BZX84C18_D87Z	onsemi	18	±6%	350	45	50 @ 12.6	900 @ 10	-55 to 150	Obsolete
BZX84C18LT1G	onsemi	18	±6%	225	45	50 @ 12.6	900 @ 10	-65 to 150	Active
BZX84C18LT3G	onsemi	18	±6%	225	45	50 @ 12.6	900 @ 10	-65 to 150	Active
BZX84-C18,215	NXP USA Inc.	18	±5%	250	45	50 @ 12.6	900 @ 10	-65 to 150	Active
BZX84-C18,235	NXP Semiconductors	18	±5%	250	45	50 @ 12.6	900 @ 10	-65 to 150	Active
BZX84B18-TP	Micro Commercial Co	18	±2%	350	45	100 @ 12.6	900 @ 10	-55 to 150	Active
BZX84C18-7-F	Diodes Incorporated	18	±6%	300	45	100 @ 12.6	900 @ 10	-65 to 150	Active
MMBZ5248B-7-F	Diodes Incorporated	18	±5%	350	21	100 @ 14	900 @ 10	-65 to 150	Active
MMBZ5248BQ-7-F	Diodes Incorporated	18	±5%	350	21	100 @ 14	900 @ 10	-65 to 150	Active
BZX84C18-TP	Micro Commercial Co	18	±5%	350	45	100 @ 12.6	900 @ 10	-55 to 150	Active

Engineering Selection Recommendations

Primary Recommendation for Direct Replacement:

BZX84C18-TP (Micro Commercial Co) and BZX84C18-7-F (Diodes Incorporated) are the preferred substitutes. Both parts maintain the 18 V nominal Zener voltage, SOT-23-3 package, and 350 mW power rating. Both manufacturers hold active product status with RoHS3 compliance and AEC-Q101 automotive qualification (BZX84C18-7-F). These parts ensure functional equivalence with the obsolete BZX84C18_D87Z.

Secondary Recommendations for Power-Constrained Applications:

BZX84C18LT1G and BZX84C18LT3G (onsemi) are active alternatives from the original manufacturer. These parts maintain electrical equivalence but feature reduced power dissipation (225 mW versus 350 mW). Selection is appropriate for applications where the 350 mW rating is not required. Both parts extend the operating temperature range to -65°C.

Alternative Suppliers with Enhanced Specifications:

MMBZ5248B-7-F and MMBZ5248BQ-7-F (Diodes Incorporated) provide 350 mW power rating with improved impedance characteristics (21 Ohms versus 45 Ohms). MMBZ5248BQ-7-F includes AEC-Q101 automotive qualification. These parts are suitable for applications requiring lower dynamic impedance.

NXP Alternatives:

BZX84-C18,215 and BZX84-C18,235 (NXP) are active alternatives with ±5% tolerance and 250 mW power rating. Both include AEC-Q101 automotive qualification. These parts are appropriate for applications where the tighter tolerance and automotive qualification are required, with adequate power margin.

Frequently Asked Questions (FAQ)

Q: Can BZX84C18LT1G replace BZX84C18_D87Z in all applications?

A: BZX84C18LT1G maintains electrical equivalence in Zener voltage, tolerance, impedance, and forward voltage characteristics. However, the power rating is reduced from 350 mW to 225 mW. Substitution is valid only if the application power dissipation does not exceed 225 mW. Verify thermal requirements before selection.

Q: What is the difference between BZX84C18-TP and BZX84C18-7-F?

A: Both parts share the same 18 V nominal voltage, ±5% to ±6% tolerance, 350 mW power rating, and SOT-23-3 package. BZX84C18-7-F (Diodes Incorporated) includes AEC-Q101 automotive qualification; BZX84C18-TP (Micro Commercial Co) does not. Selection depends on automotive qualification requirements.

Q: Why do MMBZ5248B-7-F and MMBZ5248BQ-7-F have lower impedance (21 Ohms)?

A: Lower impedance indicates reduced dynamic resistance in the Zener breakdown region. This characteristic improves voltage regulation stability under varying load conditions. Selection is appropriate for applications requiring enhanced regulation performance. Functional compatibility with the original part is maintained.

Q: Are NXP parts (BZX84-C18,215 and BZX84-C18,235) suitable replacements?

A: Yes. Both NXP parts maintain 18 V nominal voltage, SOT-23-3 package, and include AEC-Q101 automotive qualification. The ±5% tolerance is tighter than the original ±6%. Power rating is 250 mW, which is lower than the original 350 mW. Substitution is valid if application power dissipation does not exceed 250 mW.

Q: What is the significance of the extended temperature range (-65°C) in BZX84C18LT1G and BZX84C18LT3G?

A: The extended lower temperature limit (-65°C versus -55°C) provides operational capability in more severe thermal environments. This specification does not affect compatibility with applications designed for the original -55°C to 150°C range. Extended range parts are suitable for all applications within the original temperature envelope.

Q: Can I use BZX84B18-TP as a direct replacement?

A: BZX84B18-TP maintains 18 V nominal voltage, 350 mW power rating, and SOT-23-3 package. The tolerance is ±2%, which is tighter than the original ±6%. Reverse leakage current is 100 nA @ 12.6 V, compared to 50 nA in the original part. Functional compatibility is maintained; the tighter tolerance and higher leakage current do not preclude substitution.

Q: What packaging options are available for these substitute parts?

A: All substitute parts are available in SOT-23-3 (TO-236-3, SC-59) surface mount package, matching the original BZX84C18_D87Z. Packaging variants include Cut Tape (CT), Digi-Reel, and Tape & Reel (TR) options depending on the specific part number and manufacturer. Verify packaging format with supplier documentation before procurement.

Q: Are all substitute parts RoHS compliant?

A: All active substitute parts listed are RoHS3 compliant. The original BZX84C18_D87Z does not specify RoHS status due to obsolete classification. RoHS3 compliance ensures compatibility with current environmental and regulatory requirements.

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