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

onsemi BZX85C3V9

Name: BZX85C3V9
Brand: onsemi
SKU: BZX85C3V9
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BZX85C3V9

Manufacturer:: onsemi

Category:: Single Zener Diodes

Package:: DO-204AL, DO-41, Axial

Datasheet:: BZX85C3V9.pdf

Description:: DIODE ZENER 3.9V 1W DO204AL

Quantity:: RFQ Add To RFQ list

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Inventory:68,500

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Product details

Overview

BZX85C3V9 from onsemi is a 3.9 V, ±5% tolerance, 1.0 W axial-leaded Zener diode in DO-41 glass package, designed for voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and precision biasing networks where stable low-voltage clamping is required.

For engineers reviewing the BZX85C3V9 datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance (±5%), zener impedance (15 Ω @ 60 mA), leakage current (5 μA max @ 1 V), thermal derating (6.67 mW/°C above 50°C), and DO-41 mechanical compatibility with through-hole PCB assembly.

Technical Context

The BZX85C3V9 operates as a silicon planar Zener diode with controlled avalanche breakdown at nominal 3.9 V, specified under thermal equilibrium conditions at lead temperature TL = 30°C ±1°C and 3/8″ lead length. Its 1.0 W power rating at 25°C ambient enables robust transient suppression in low-to-medium current regulation paths.

Zener impedance is characterized at IZ = 60 mA (ZZ = 15 Ω) and at knee current IZK = 1 mA (ZZK = 500 Ω), supporting both stable regulation and low-current reference use. Forward voltage is 1.2 V max at 200 mA, confirming standard PN junction behavior for bidirectional circuit analysis.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	3.7 V min to 4.1 V max - defines regulated output range under 60 mA test current; ±5% tolerance ensures predictable clamping in feedback networks.
Power Dissipation (P_D)	1.0 W @ T_A = 25°C - sets maximum continuous power handling before thermal derating begins at 50°C.
Zener Impedance (Z_Z)	15 Ω @ I_Z = 60 mA - indicates low dynamic resistance for minimal output voltage variation under load changes.
Leakage Current (I_R)	5 μA max @ V_R = 1 V - confirms negligible reverse conduction below breakdown, critical for low-power standby circuits.
Operating Temperature	−65°C to +200°C - supports deployment in automotive engine compartments, industrial controls, and high-reliability environments.
Forward Voltage (V_F)	1.2 V max @ I_F = 200 mA - enables accurate forward-bias modeling in dual-direction protection or clamp-assisted startup circuits.

Pinout & Package

DO-41 glass axial package with cathode indicated by color band; two-terminal device requiring no orientation-specific PCB footprint beyond standard 0.4″ lead spacing.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward current entry / Reverse breakdown reference node	Connected to lower-potential side of regulated node; used for biasing, sensing, or current sourcing in shunt regulator topologies.
Cathode	Zener breakdown terminal / Reference voltage output	Marked with color band; delivers stable 3.9 V reference when reverse-biased; ties to regulated rail or error amplifier input.

Key Features

Feature	Design Value
±5% Zener voltage tolerance	Enables consistent regulation across production batches without post-assembly trimming in cost-sensitive consumer and industrial supplies.
Low Zener impedance (15 Ω)	Minimizes output voltage deviation under varying load currents, improving stability in closed-loop feedback systems like SMPS voltage references.
DO-41 glass package	Provides hermetic sealing and high-temperature reliability up to +200°C, suitable for under-hood automotive and high-temp industrial modules.
1.0 W power rating	Supports direct shunt regulation of up to ~250 mA at 3.9 V without external heat sinking in compact board layouts.

Applications

Switch-Mode Power Supply Feedback	Microcontroller Reset Circuit
Use Scenario: Provides precise 3.9 V reference for optocoupler-based feedback in isolated AC/DC converters. IC Role / Device Role: Shunt voltage reference enabling secondary-side regulation without auxiliary winding. Use Value: Maintains ±1% output accuracy over line/load/temperature due to tight 3.9 V tolerance and low ZZ.	Use Scenario: Generates clean reset signal for 3.3 V microcontrollers during power-up and brownout events. IC Role / Device Role: Threshold detector that triggers reset IC or MCU internal POR when V_CC drops below 3.9 V. Use Value: Low leakage (5 μA) prevents excessive current draw in sleep mode; DO-41 allows easy hand-soldering in prototyping.
Overvoltage Clamp for Sensor Inputs	Reference Voltage for Analog Front-Ends
Use Scenario: Protects ADC inputs from ESD or transient spikes exceeding 3.9 V in industrial sensor interfaces. IC Role / Device Role: Bidirectional transient suppressor leveraging Zener action in reverse and 1.2 V forward drop in positive transients. Use Value: Fast response (<1 ns) and low clamping voltage prevent damage to 3.3 V analog inputs while maintaining signal integrity.	Use Scenario: Supplies stable 3.9 V reference for op-amp biasing or DAC reference in battery-powered instrumentation. IC Role / Device Role: Low-drift voltage source with minimal self-heating due to 1.0 W rating and DO-41 thermal mass. Use Value: 15 Ω Z_Z ensures <0.1% reference shift per 1 mA load change-critical for 12-bit+ measurement accuracy.

Switch-Mode Power Supply Feedback

Microcontroller Reset Circuit

Use Scenario: Provides precise 3.9 V reference for optocoupler-based feedback in isolated AC/DC converters.

IC Role / Device Role: Shunt voltage reference enabling secondary-side regulation without auxiliary winding.

Use Value: Maintains ±1% output accuracy over line/load/temperature due to tight 3.9 V tolerance and low ZZ.

Use Scenario: Generates clean reset signal for 3.3 V microcontrollers during power-up and brownout events.

IC Role / Device Role: Threshold detector that triggers reset IC or MCU internal POR when V_CC drops below 3.9 V.

Use Value: Low leakage (5 μA) prevents excessive current draw in sleep mode; DO-41 allows easy hand-soldering in prototyping.

Overvoltage Clamp for Sensor Inputs

Reference Voltage for Analog Front-Ends

Use Scenario: Protects ADC inputs from ESD or transient spikes exceeding 3.9 V in industrial sensor interfaces.

IC Role / Device Role: Bidirectional transient suppressor leveraging Zener action in reverse and 1.2 V forward drop in positive transients.

Use Value: Fast response (<1 ns) and low clamping voltage prevent damage to 3.3 V analog inputs while maintaining signal integrity.

Use Scenario: Supplies stable 3.9 V reference for op-amp biasing or DAC reference in battery-powered instrumentation.

IC Role / Device Role: Low-drift voltage source with minimal self-heating due to 1.0 W rating and DO-41 thermal mass.

Use Value: 15 Ω Z_Z ensures <0.1% reference shift per 1 mA load change-critical for 12-bit+ measurement accuracy.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4729A	Zener voltage 4.0 V (±5%), P_D = 1.0 W, DO-41, Z_Z = 10 Ω @ 60 mA	Slightly higher nominal voltage; tighter Z_Z improves regulation but may require minor feedback resistor recalibration.	Select when 4.0 V nominal matches system reference target and lower impedance is prioritized over exact 3.9 V match.
BZX55C3V9	Zener voltage 3.9 V (±5%), P_D = 500 mW, DO-35 glass, Z_Z = 15 Ω @ 60 mA	Half the power rating limits current capability; smaller DO-35 footprint reduces board space but increases thermal stress at full load.	Choose for space-constrained designs where ≤125 mA regulation suffices and DO-35 mounting is preferred.

Compared with BZX85C3V9, the 1N4729A offers marginally better regulation stability at 4.0 V, while the BZX55C3V9 trades power handling for compactness-making BZX85C3V9 optimal for 3.9 V, 1 W, DO-41-restricted designs.

Availability

BZX85C3V9 is available at Aetrix Electronics and suitable for switch-mode power supplies, microcontroller reset circuits, sensor input protection, and analog front-end references requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for BZX85C3V9 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 (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BZX85 series was engineered for general-purpose voltage regulation and reference applications, emphasizing rugged DO-41 packaging, wide temperature operation, and consistent Zener performance across voltage grades from 3.3 V to 56 V.

FAQ

What is the maximum reverse leakage current for BZX85C3V9?

The BZX85C3V9 has a maximum reverse leakage current of 5 μA at 1 V reverse voltage (V_R), measured at 25°C. This low leakage ensures minimal quiescent current draw in battery-powered or low-power monitoring circuits where the BZX85C3V9 serves as a reference or clamp. The specification is confirmed in the official onsemi datasheet Rev. 2 (October 2017).

Is BZX85C3V9 compatible with automated through-hole assembly?

Yes, the BZX85C3V9 uses the standard DO-41 axial package with 0.4″ (10.16 mm) lead spacing and JEDEC-compliant dimensions, making it fully compatible with automated insertion and wave soldering equipment. Its glass body and color-band cathode marking support optical recognition and polarity verification during placement-key for high-yield BZX85C3V9 manufacturing runs.

Does BZX85C3V9 meet automotive AEC-Q200 requirements?

No, the BZX85C3V9 is not AEC-Q200 qualified. While it operates from −65°C to +200°C and uses a glass DO-41 package, onsemi does not list this part in its AEC-Q200 stress-tested portfolio. For automotive applications requiring qualification, engineers should consider the AEC-Q200–rated equivalents such as the 1N4729A-Q or NZ9F3V9T5G, not the BZX85C3V9.

What is the thermal derating slope for BZX85C3V9 above 50°C?

The BZX85C3V9 derates linearly at 6.67 mW/°C above an ambient temperature of 50°C, reducing its maximum allowable power dissipation from 1.0 W at 25°C to zero at approximately 200°C. This slope is defined in the Absolute Maximum Ratings table and must be applied in thermal design calculations for BZX85C3V9 in enclosed or high-ambient environments.

Can BZX85C3V9 be used in forward-bias applications?

Yes, the BZX85C3V9 exhibits a forward voltage of 1.2 V maximum at 200 mA, allowing use as a standard silicon diode in low-voltage rectification or polarity protection roles. However, its primary design intent-and validated specifications-are for reverse-bias Zener operation; forward characteristics are secondary and not optimized for high-efficiency rectification like Schottky diodes.

BZX85C3V9 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: DO-204AL, DO-41, Axial

Packaging:: Bulk

Product Status:: Active

Voltage - Zener (Nom) (Vz):: 3.9 V

Tolerance:: ±5%

Power - Max:: 1 W

Impedance (Max) (Zzt):: 15 Ohms

Current - Reverse Leakage @ Vr:: 5 µA @ 1 V

Voltage - Forward (Vf) (Max) @ If:: 1.2 V @ 200 mA

Operating Temperature:: -65°C ~ 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-204AL (DO-41)

BZX85C3V9 FAQ

1.How can I place an order for BZX85C3V9 through Aetrix?

Please submit a Request for Quotation (RFQ) for BZX85C3V9 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 BZX85C3V9 reliable?

The price and inventory of BZX85C3V9 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BZX85C3V9 is usually 5 days.

3.What payment methods are accepted for BZX85C3V9?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BZX85C3V9 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BZX85C3V9?

BZX85C3V9 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BZX85C3V9 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 BZX85C3V9?

For technical support, including BZX85C3V9 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BZX85C3V9 requirements.

6.How does Aetrix verify that BZX85C3V9 is sourced from the original manufacturer or authorized distributors?

All BZX85C3V9 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 BZX85C3V9 meets industry standards.

7.What is the process for return or replacement of BZX85C3V9?

All BZX85C3V9 units undergo pre-shipment inspection (PSI). If there is an issue with BZX85C3V9, 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 BZX85C3V9 part is unused and in its original packaging.

Return procedure for BZX85C3V9:

1.Submit a request within 90 days.

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

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