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Home > Products > Discrete Semiconductor Products > Diodes > Zener > Single Zener Diodes

onsemi BZX84C18LT3G

Name: BZX84C18LT3G
Brand: onsemi
SKU: BZX84C18LT3G
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BZX84C18LT3G

Manufacturer:: onsemi

Category:: Single Zener Diodes

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: BZX84C18LT3G.pdf

Description:: DIODE ZENER 18V 250MW SOT23-3

Quantity:: RFQ Add To RFQ list

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Inventory:40,041

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Product details

Overview

BZX84C18LT3G from onsemi is a 250 mW, 18 V nominal Zener voltage regulator diode in SOT-23 package, designed for precision voltage reference and overvoltage protection in space-constrained circuits. It delivers ±5% tolerance at 5 mA test current, 45 Ω dynamic impedance, and operates across −65°C to +150°C junction temperature range. It is used in power supply feedback loops, voltage clamping in portable electronics, and ESD-sensitive analog front-ends.

For engineers reviewing the BZX84C18LT3G datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage tolerance (±5%), thermal resistance (500 °C/W on FR-5), cathode-anode polarity marking, and Class 3 ESD rating (>16 kV HBM) - all critical for low-power, high-density board designs requiring stable regulation under transient stress.

Technical Context

This device functions as a two-terminal shunt voltage regulator, maintaining a stable 18 V reverse breakdown voltage across its cathode–anode terminals when biased above IZT = 5 mA. Its operation relies on controlled avalanche breakdown, with temperature coefficient of +12.6 mV/°C ensuring predictable drift over industrial temperature ranges.

The SOT-23 package features pin 1 (anode), pin 2 (no connection), and pin 3 (cathode), with polarity indicated by a band on the cathode end. Its 250 mW power rating is derated linearly above 25°C at 2.0 mW/°C on FR-5 board, supporting reliable operation in thermally constrained environments.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	16.8 V min / 18.0 V nom / 19.1 V max @ I_ZT = 5 mA - defines regulation window for feedback or clamp circuits.
Zener Impedance (Z_ZT)	45 Ω max @ I_ZT = 5 mA - determines output voltage stability under load current variation.
Reverse Leakage Current	0.05 μA max @ V_R = 13.7 V - ensures minimal quiescent current in standby or high-impedance bias networks.
Power Dissipation	250 mW on FR-5 board @ T_A = 25°C - sets maximum continuous power handling before thermal derating applies.
Temperature Coefficient	+12.6 mV/°C @ I_ZT = 5 mA - quantifies voltage drift per degree, critical for temperature-critical references.
Capacitance	100 pF @ V_R = 0 V, f = 1 MHz - impacts high-frequency noise filtering and signal integrity in RF-adjacent nodes.
ESD Rating	Class 3 (>16 kV) per Human Body Model - enables direct placement near connectors or I/O without external protection.

Pinout & Package

SOT-23 (TO-236) surface-mount plastic package, 2.90 mm × 1.30 mm × 1.00 mm, void-free thermosetting case with corrosion-resistant finish. Cathode identified by band; maximum soldering temperature 260°C for 10 seconds. UL 94 V-0 flammability rating.

Pin/Terminal	Circuit Role	Design Meaning
1	Anode	Connected to lower-potential node in shunt regulation; reverse-biased during Zener operation.
2	No Connection	Internally unconnected; must remain floating - no PCB trace or pad required.
3	Cathode	Connected to regulated voltage node; polarity band aligns with this terminal for visual orientation.

Key Features

Feature	Design Value
250 mW power rating on FR-5 board	Enables compact voltage reference design without heatsinking in handheld and IoT devices.
±5% Zener voltage tolerance at 5 mA	Supports cost-effective regulation where tight accuracy is not required, reducing BOM complexity.
Class 3 ESD protection (>16 kV HBM)	Eliminates need for discrete ESD diodes in low-voltage I/O protection schemes.
Pb-free and RoHS-compliant construction	Meets global environmental compliance requirements for industrial and consumer production.
Tight thermal resistance control (500 °C/W)	Allows predictable thermal modeling in multi-layer PCB layouts with limited copper area.

Applications

Power Supply Feedback Reference	Overvoltage Clamp for Microcontroller I/O
Use Scenario: Stabilizing output voltage in adjustable DC-DC converter feedback network using TL431 or similar error amplifier. IC Role / Device Role / Timing Role: Provides precise 18 V reference point for comparator input, enabling accurate output setpoint control. Use Value: Maintains ±5% regulation accuracy across temperature, minimizing output drift without trimming resistors.	Use Scenario: Protecting 3.3 V or 5 V GPIO pins from accidental 12–24 V miswiring or inductive kickback. IC Role / Device Role / Timing Role: Shunt clamp that conducts above 19.1 V, limiting voltage seen by downstream logic inputs. Use Value: Absorbs transient energy up to 250 mW without latch-up, preserving MCU functionality during fault events.
Low-Power Sensor Biasing	ESD Protection for Analog Front-Ends
Use Scenario: Generating stable bias voltage for op-amp rail-to-rail sensors operating near 18 V supply rails. IC Role / Device Role / Timing Role: Supplies low-noise, low-drift reference to sensor excitation circuitry in battery-powered instrumentation. Use Value: Delivers 100 pF capacitance and <0.05 μA leakage, minimizing loading and offset errors in high-impedance paths.	Use Scenario: Safeguarding ADC input channels exposed to user-accessible ports in medical or test equipment. IC Role / Device Role / Timing Role: First-line defense against ESD events, clamping fast transients before they reach sensitive silicon. Use Value: Withstands >16 kV HBM strikes while adding negligible parasitic capacitance to signal path.

Power Supply Feedback Reference

Overvoltage Clamp for Microcontroller I/O

Use Scenario: Stabilizing output voltage in adjustable DC-DC converter feedback network using TL431 or similar error amplifier.

IC Role / Device Role / Timing Role: Provides precise 18 V reference point for comparator input, enabling accurate output setpoint control.

Use Value: Maintains ±5% regulation accuracy across temperature, minimizing output drift without trimming resistors.

Use Scenario: Protecting 3.3 V or 5 V GPIO pins from accidental 12–24 V miswiring or inductive kickback.

IC Role / Device Role / Timing Role: Shunt clamp that conducts above 19.1 V, limiting voltage seen by downstream logic inputs.

Use Value: Absorbs transient energy up to 250 mW without latch-up, preserving MCU functionality during fault events.

Low-Power Sensor Biasing

ESD Protection for Analog Front-Ends

Use Scenario: Generating stable bias voltage for op-amp rail-to-rail sensors operating near 18 V supply rails.

IC Role / Device Role / Timing Role: Supplies low-noise, low-drift reference to sensor excitation circuitry in battery-powered instrumentation.

Use Value: Delivers 100 pF capacitance and <0.05 μA leakage, minimizing loading and offset errors in high-impedance paths.

Use Scenario: Safeguarding ADC input channels exposed to user-accessible ports in medical or test equipment.

IC Role / Device Role / Timing Role: First-line defense against ESD events, clamping fast transients before they reach sensitive silicon.

Use Value: Withstands >16 kV HBM strikes while adding negligible parasitic capacitance to signal path.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener regulation applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BZX84C18LT1G	Same electrical specs, but supplied in 3,000-piece tape-and-reel vs. 10,000-piece for BZX84C18LT3G.	Identical performance; preferred for prototyping or low-volume builds due to smaller reel size.	Select BZX84C18LT1G when order quantity or inventory turnover favors smaller reels.
BZX84B18LT1G	Tighter ±2% tolerance (vs. ±5%), higher test current (IZT = 5 mA), same 18 V nominal, 45 Ω Z_ZT.	Better suited for precision references where voltage stability outweighs cost sensitivity.	Choose BZX84B18LT1G when system-level accuracy demands tighter initial tolerance and lower TC drift.

Compared with BZX84C18LT3G, BZX84C18LT1G offers identical regulation performance in a smaller reel format ideal for evaluation, while BZX84B18LT1G trades wider tolerance for improved accuracy-making it suitable for metrology-grade biasing where ±2% matters more than unit cost.

Availability

BZX84C18LT3G is available at Aetrix Electronics and suitable for power supply feedback, overvoltage clamping, and low-power sensor biasing requiring stable component supply, consistent Pb-free compliance, and high-volume tape-and-reel logistics.

Supply support for BZX84C18LT3G includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

onsemi (Semiconductor Components Industries, LLC) is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

BZX84C18LT3G belongs to the BZX84CxxxLTxG series of standard-tolerance Zener regulators, engineered for cost-sensitive, high-density applications where robustness, small footprint, and ESD resilience are prioritized over ultra-precise voltage matching.

FAQ

What is the Zener voltage tolerance of BZX84C18LT3G?

The BZX84C18LT3G has a nominal Zener voltage of 18.0 V with a tolerance of ±5%, meaning its actual breakdown voltage falls between 16.8 V and 19.1 V when tested at I_ZT = 5 mA and T_A = 25°C. This tolerance reflects the standard grade of the BZX84C series, distinguishing it from the tighter ±2% BZX84B variant.

Can BZX84C18LT3G be used as a replacement for BZX84C18LT1G?

Yes, BZX84C18LT3G is electrically identical to BZX84C18LT1G - same Zener voltage, impedance, leakage, and thermal specs - differing only in packaging quantity (10,000 vs. 3,000 pieces per reel). No circuit or layout changes are needed; the substitution is fully compatible for production scaling or inventory optimization.

What is the maximum power dissipation of BZX84C18LT3G on an FR-5 board?

BZX84C18LT3G is rated for 250 mW total power dissipation on FR-5 board at ambient temperature of 25°C. Above 25°C, it derates linearly at 2.0 mW/°C, reaching zero dissipation capability at 150°C ambient. This rating assumes standard JEDEC-defined board conditions and must be validated against actual PCB thermal design.

How is polarity marked on the BZX84C18LT3G SOT-23 package?

The BZX84C18LT3G uses a cathode band to indicate polarity: the banded end corresponds to pin 3 (cathode), while pin 1 (anode) is at the opposite end. Pin 2 is internally unconnected and must remain unattached on the PCB. This marking aligns with SOT-23 Style 8 mechanical outline defined in the onsemi package documentation.

Does BZX84C18LT3G meet automotive qualification standards?

No - BZX84C18LT3G is part of the commercial-grade BZX84C series. For automotive applications, the SZBZX84C18LT3G variant is AEC-Q101 qualified and PPAP capable. The "SZ" prefix denotes automotive-specific manufacturing controls, while BZX84C18LT3G is intended for industrial, consumer, and general-purpose use.

BZX84C18LT3G Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: BZX84CxxxLT1G

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Active

Voltage - Zener (Nom) (Vz):: 18 V

Tolerance:: ±6%

Power - Max:: 250 mW

Impedance (Max) (Zzt):: 45 Ohms

Current - Reverse Leakage @ Vr:: 50 nA @ 12.6 V

Voltage - Forward (Vf) (Max) @ If:: 900 mV @ 10 mA

Operating Temperature:: -65°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3 (TO-236)

BZX84C18LT3G FAQ

1.How can I place an order for BZX84C18LT3G through Aetrix?

Please submit a Request for Quotation (RFQ) for BZX84C18LT3G on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BZX84C18LT3G reliable?

The price and inventory of BZX84C18LT3G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BZX84C18LT3G is usually 5 days.

3.What payment methods are accepted for BZX84C18LT3G?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BZX84C18LT3G transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BZX84C18LT3G?

BZX84C18LT3G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BZX84C18LT3G order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BZX84C18LT3G?

For technical support, including BZX84C18LT3G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BZX84C18LT3G requirements.

6.How does Aetrix verify that BZX84C18LT3G is sourced from the original manufacturer or authorized distributors?

All BZX84C18LT3G products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BZX84C18LT3G meets industry standards.

7.What is the process for return or replacement of BZX84C18LT3G?

All BZX84C18LT3G units undergo pre-shipment inspection (PSI). If there is an issue with BZX84C18LT3G, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BZX84C18LT3G part is unused and in its original packaging.

Return procedure for BZX84C18LT3G:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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