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

onsemi SZ1SMA5939BT3G

Name: SZ1SMA5939BT3G
Brand: onsemi
SKU: SZ1SMA5939BT3G
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SZ1SMA5939BT3G

Manufacturer:: onsemi

Category:: Single Zener Diodes

Package:: DO-214AC, SMA

Datasheet:: SZ1SMA5939BT3G.pdf

Description:: DIODE ZENER 39V 1.5W SMA

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Product details

Overview

SZ1SMA5939BT3G from onsemi is a 1.5 W surface-mount Zener diode with nominal zener voltage of 39 V, maximum zener impedance of 9.6 Ω at 45 mA test current, and reverse leakage current ≤0.25 μA at 31.7 V. It operates across −65 °C to +150 °C and is AEC−Q101 qualified for automotive applications requiring stable voltage regulation in power supply rails and overvoltage protection circuits.

For engineers reviewing the SZ1SMA5939BT3G datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance (±5%), thermal resistance (50 °C/W junction-to-lead), low-profile SMA package compatibility, and ESD robustness (>16 kV HBM).

Technical Context

This device functions as a precision voltage reference and shunt regulator in DC power conditioning circuits. Its 39 V nominal breakdown voltage is guaranteed at thermal equilibrium with ±5% tolerance, and it maintains regulation under DC zener current up to 29.7 mA at rated power dissipation.

The SMA package enables top-slide or bottom-board mounting with flat handling surface and Pb-free construction. Thermal derating begins at 75 °C (20 mW/°C), and junction-to-lead thermal resistance is fixed at 50 °C/W - critical for thermal design in compact automotive and industrial PCB layouts.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	37.05 V (min) to 40.95 V (max) at I_ZT = 45 mA - defines regulated output range under nominal bias
Zener Impedance (Z_ZT)	9.6 Ω max at I_ZT = 45 mA - determines AC ripple rejection and regulation stability
Max DC Power Dissipation	1.5 W @ T_L = 75 °C - sets absolute thermal limit with zero-lead-length mounting condition
Reverse Leakage Current	≤0.25 μA at V_R = 31.7 V - ensures minimal standby power loss in high-impedance bias networks
Junction-to-Lead Thermal Resistance	50 °C/W - enables direct thermal path modeling from die to PCB copper pad
ESD Rating (HBM)	Class 3 (>16 kV) - supports robust handling in automated SMT assembly without external protection
Operating Temperature Range	−65 °C to +150 °C - validated for under-hood automotive and industrial ambient conditions

Pinout & Package

The SZ1SMA5939BT3G is housed in an SMA (DO-214AC) surface-mount plastic package (Case 403D, Style 1), featuring a molded cathode band for polarity identification and corrosion-resistant, solderable leads. Maximum soldering temperature is 260 °C for 10 seconds.

Pin/Terminal	Circuit Role	Design Meaning
Cathode (marked band)	Zener anode connection point	Connected to regulated output node; carries full zener current during regulation
Anode	Zener cathode connection point	Connected to reference or ground potential; establishes reverse-bias polarity

Key Features

Feature	Design Value
AEC−Q101 qualification	Validated reliability for automotive power management systems including engine control units and body electronics
Low-profile SMA package	Enables board-space-constrained designs where MELF or axial-leaded devices are impractical
Flat handling surface	Ensures consistent pick-and-place accuracy during high-speed SMT assembly
UL 94 V−0 flammability rating	Meets safety requirements for enclosed industrial and transportation equipment enclosures
Pb-free construction	Complies with RoHS Directive 2011/65/EU and JEDEC J-STD-020 reflow profile standards

Applications

Automotive Engine Control Unit (ECU) Reference	Industrial PLC Analog Input Protection
Use Scenario: Stabilizing 39 V reference rail for sensor signal conditioning in harsh under-hood environments. IC Role / Device Role / Timing Role: Shunt voltage regulator providing precise, temperature-stable reference for ADC front-end circuitry. Use Value: Maintains <±1% regulation error across −40 °C to +125 °C ambient due to low dynamic impedance (9.6 Ω) and AEC−Q101 validation.	Use Scenario: Clamping transient overvoltage on 24 V analog input channels exposed to inductive switching noise. IC Role / Device Role / Timing Role: Overvoltage protection element diverting surge energy away from precision op-amps and ADCs. Use Value: Limits peak voltage to ≤41 V while sustaining 29.7 mA continuous current - sufficient for sustained fault conditions per IEC 61000-4-4.
Telecom Power Supply Feedback Loop	Medical Diagnostic Equipment Bias Supply
Use Scenario: Providing feedback reference for isolated flyback converter regulating +39 V auxiliary rail in base station power modules. IC Role / Device Role / Timing Role: Precision voltage reference in optocoupler-coupled feedback path. Use Value: Delivers ±5% tolerance and <10 Ω dynamic impedance to minimize loop gain variation and improve load regulation (<±2%).	Use Scenario: Generating stable bias voltage for photodiode amplifier stages in portable ultrasound imaging front-ends. IC Role / Device Role / Timing Role: Low-noise shunt regulator supplying clean 39 V to high-gain transimpedance amplifiers. Use Value: Achieves <0.25 μA leakage at 31.7 V, reducing input offset drift and enabling sub-picoampere current measurement fidelity.

Automotive Engine Control Unit (ECU) Reference

Industrial PLC Analog Input Protection

Use Scenario: Stabilizing 39 V reference rail for sensor signal conditioning in harsh under-hood environments.

IC Role / Device Role / Timing Role: Shunt voltage regulator providing precise, temperature-stable reference for ADC front-end circuitry.

Use Value: Maintains <±1% regulation error across −40 °C to +125 °C ambient due to low dynamic impedance (9.6 Ω) and AEC−Q101 validation.

Use Scenario: Clamping transient overvoltage on 24 V analog input channels exposed to inductive switching noise.

IC Role / Device Role / Timing Role: Overvoltage protection element diverting surge energy away from precision op-amps and ADCs.

Use Value: Limits peak voltage to ≤41 V while sustaining 29.7 mA continuous current - sufficient for sustained fault conditions per IEC 61000-4-4.

Telecom Power Supply Feedback Loop

Medical Diagnostic Equipment Bias Supply

Use Scenario: Providing feedback reference for isolated flyback converter regulating +39 V auxiliary rail in base station power modules.

IC Role / Device Role / Timing Role: Precision voltage reference in optocoupler-coupled feedback path.

Use Value: Delivers ±5% tolerance and <10 Ω dynamic impedance to minimize loop gain variation and improve load regulation (<±2%).

Use Scenario: Generating stable bias voltage for photodiode amplifier stages in portable ultrasound imaging front-ends.

IC Role / Device Role / Timing Role: Low-noise shunt regulator supplying clean 39 V to high-gain transimpedance amplifiers.

Use Value: Achieves <0.25 μA leakage at 31.7 V, reducing input offset drift and enabling sub-picoampere current measurement fidelity.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1SMA5939BT3G	No SZ prefix; commercial-grade (non-AEC−Q101 qualified); identical electrical specs and package	Not suitable for automotive production; acceptable for industrial prototypes and non-safety-critical systems	Select when AEC−Q101 qualification is not required and cost optimization is prioritized
MMSZ5267ET1G	Lower power rating (500 mW), higher zener impedance (17 Ω), different package (SOD-123), ±5% tolerance	Limited to low-current biasing and signal-level clamping; unsuitable for >15 mA continuous regulation	Choose only for space-constrained designs where 1.5 W dissipation is unnecessary and thermal margin is ample

Compared with 1SMA5939BT3G and MMSZ5267ET1G, the SZ1SMA5939BT3G uniquely combines automotive qualification, 1.5 W power handling, and 9.6 Ω dynamic impedance - making it the sole option for thermally demanding, safety-compliant 39 V regulation in production vehicles and industrial controls.

Availability

SZ1SMA5939BT3G is available at Aetrix Electronics and suitable for automotive ECU design, industrial PLC analog input protection, and telecom power supply feedback loops requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for SZ1SMA5939BT3G 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.

The 1SMA59xxBT3G/SZ1SMA59xxBT3G series was designed specifically for surface-mount voltage regulation and overvoltage protection in space-constrained, high-reliability systems - emphasizing AEC−Q101 compliance, low-profile packaging, and robust ESD performance.

FAQ

What is the zener voltage tolerance for SZ1SMA5939BT3G?

The SZ1SMA5939BT3G has a zener voltage tolerance of ±5%, with a nominal value of 39 V and guaranteed limits of 37.05 V (minimum) and 40.95 V (maximum) at I_ZT = 45 mA and thermal equilibrium. This tolerance is specified per the onsemi datasheet Rev. 11 and applies directly to the SZ1SMA5939BT3G device marking "839B".

Is SZ1SMA5939BT3G suitable for automotive applications?

Yes, SZ1SMA5939BT3G is AEC−Q101 qualified and PPAP capable, making it suitable for automotive applications such as engine control units, body control modules, and ADAS power supplies. The SZ prefix explicitly denotes automotive-grade qualification, and the device meets stringent reliability and thermal cycling requirements defined in the AEC−Q101 standard.

What is the maximum DC zener current for SZ1SMA5939BT3G?

The maximum DC zener current (I_ZM) for SZ1SMA5939BT3G is 29.7 mA at rated power dissipation. This value is derived from the 1.5 W power rating and nominal 39 V zener voltage (I_ZM = P_D/V_Z ≈ 1.5 W / 39 V), and is confirmed in the Electrical Characteristics table on page 2 of the onsemi datasheet for SZ1SMA5939BT3G.

Does SZ1SMA5939BT3G have ESD protection?

Yes, SZ1SMA5939BT3G features an ESD rating of Class 3 (>16 kV) per the Human Body Model (HBM), as stated in the Features section of the onsemi datasheet. This level of ESD robustness eliminates the need for additional external protection during automated SMT assembly and improves field reliability in electrostatic-prone environments.

What package type does SZ1SMA5939BT3G use?

SZ1SMA5939BT3G uses the SMA (DO-214AC) surface-mount package, also designated Case 403D Style 1. It features a molded cathode band for polarity identification, Pb-free construction, and UL 94 V−0 flammability rating - all confirmed in the Mechanical Characteristics and Ordering Information sections of the official onsemi datasheet.

SZ1SMA5939BT3G Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: SZ1SMA59xxBT3G

Package/Case:: DO-214AC, SMA

Packaging:: Tape & Reel (TR)

Product Status:: Active

Voltage - Zener (Nom) (Vz):: 39 V

Tolerance:: ±5%

Power - Max:: 1.5 W

Impedance (Max) (Zzt):: 45 Ohms

Current - Reverse Leakage @ Vr:: 500 nA @ 29.7 V

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

Operating Temperature:: -65°C ~ 150°C

Grade:: Automotive

Qualification:: AEC-Q101

Mounting Type:: Surface Mount

Supplier Device Package:: SMA

SZ1SMA5939BT3G FAQ

1.How can I place an order for SZ1SMA5939BT3G through Aetrix?

Please submit a Request for Quotation (RFQ) for SZ1SMA5939BT3G 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 SZ1SMA5939BT3G reliable?

The price and inventory of SZ1SMA5939BT3G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SZ1SMA5939BT3G is usually 5 days.

3.What payment methods are accepted for SZ1SMA5939BT3G?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SZ1SMA5939BT3G transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SZ1SMA5939BT3G?

SZ1SMA5939BT3G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SZ1SMA5939BT3G 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 SZ1SMA5939BT3G?

For technical support, including SZ1SMA5939BT3G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SZ1SMA5939BT3G requirements.

6.How does Aetrix verify that SZ1SMA5939BT3G is sourced from the original manufacturer or authorized distributors?

All SZ1SMA5939BT3G 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 SZ1SMA5939BT3G meets industry standards.

7.What is the process for return or replacement of SZ1SMA5939BT3G?

All SZ1SMA5939BT3G units undergo pre-shipment inspection (PSI). If there is an issue with SZ1SMA5939BT3G, 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 SZ1SMA5939BT3G part is unused and in its original packaging.

Return procedure for SZ1SMA5939BT3G:

1.Submit a request within 90 days.

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

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