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onsemi SZ1SMB5945BT3G
- Part No.:
- SZ1SMB5945BT3G
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SZ1SMB5945BT3G.pdf
- Description:
- DIODE ZENER 68V 3W SMB
- Quantity:
- Payment:
- Shipping:
Inventory:2,504
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Product details
Overview
SZ1SMB5945BT3G from onsemi is a 3 W surface-mount Zener diode with nominal zener voltage of 68 V, ±5% tolerance, 5.5 mA test current (IZT), and maximum zener impedance of 1700 Ω at IZT - designed for precision DC voltage regulation in power supply feedback loops and overvoltage protection circuits.
For engineers reviewing the SZ1SMB5945BT3G datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage stability across temperature, low leakage (<0.25 μA at VR = 51.7 V), surge power capability (up to 100 W nonrepetitive), AEC-Q101 qualification for automotive use, and SMB package thermal performance (RJA = 226 °C/W).
Technical Context
This device operates as a two-terminal voltage reference, clamping reverse voltage at 68 V with specified dynamic impedance and temperature coefficient (θVZ ≈ +0.075 mV/°C above 6.2 V). It maintains regulation under steady-state DC load and transient surges up to 10 ms per Figure 2.
Designed for top-side or bottom-side PCB mounting in SMB (Case 403A) plastic package, it features a cathode polarity band, Pb-free construction, UL 94 V-0 flammability rating, and 260°C soldering tolerance - meeting automotive-grade reliability requirements per AEC-Q101.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 64.6 V (min) to 71.4 V (max) at IZT = 5.5 mA - defines regulated output range for feedback or clamp operation |
| Power Dissipation (PD) | 3.0 W @ TL = 75°C - supports continuous regulation in thermally constrained layouts with lead heat sinking |
| Zener Impedance (ZZT) | 1700 Ω max @ IZT = 5.5 mA - indicates voltage stability under small-signal AC variations in reference applications |
| Reverse Leakage (IR) | 0.25 μA max @ VR = 51.7 V - ensures minimal standby current in high-impedance bias networks |
| Max Zener Current (IZM) | 22 A - sets absolute DC current limit before thermal runaway; derated above 75°C |
| Thermal Resistance (RJA) | 226 °C/W - determines junction temperature rise in still-air conditions on FR-4 board |
| ESD Rating | Class 3 (>16 kV HBM) - enables robust handling in automated assembly without additional ESD protection |
Pinout & Package
Package: SMB (Case 403A), surface-mount plastic package with modified L-bend leads, cathode indicated by polarity band, dimensions 4.06 mm × 2.74 mm × 2.26 mm (L × W × H).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Reference ground node | Connected to circuit common or low-side return; establishes reference potential for zener operation |
| Cathode | Zener regulation terminal / Output node | Provides stable 68 V reference when reverse-biased; connects to feedback point or protected rail |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive powertrain and body electronics requiring extended temperature (-65°C to +150°C) and reliability compliance |
| ESD robustness >16 kV HBM | Eliminates need for external ESD protection during SMT placement and board handling |
| Flat handling surface | Enables precise pick-and-place alignment and consistent solder joint formation on fine-pitch pads |
| Pb-free and RoHS compliant | Meets global environmental regulations and supports lead-free reflow profiles (260°C/10 s) |
| Top- or bottom-side mountable | Supports dual-sided PCB assembly and compact layout in space-constrained modules |
Applications
| Automotive Power Supply Feedback | Industrial DC-DC Converter Clamp |
|---|---|
Use Scenario: Regulating output voltage in 12 V/24 V automotive buck converters where primary-side feedback requires stable reference under load transients. IC Role / Device Role / Timing Role: Zener reference element in optocoupler feedback network, providing fixed 68 V threshold for secondary-side error detection. Use Value: Maintains <±1% output regulation across -40°C to +125°C ambient due to low θVZ drift and AEC-Q101 thermal cycling validation. |
Use Scenario: Clamping transient overvoltage spikes on 48 V industrial bus lines caused by inductive switching or lightning-induced surges. IC Role / Device Role / Timing Role: Standalone overvoltage protector placed across bus rails, absorbing energy up to 100 W peak pulse (10 ms). Use Value: Limits rail voltage to ≤71.4 V during fault events, protecting downstream MOSFETs and controllers rated for 80 V max. |
| LED Driver Overvoltage Protection | Test Equipment Voltage Reference |
Use Scenario: Safeguarding constant-current LED drivers against input surge events in outdoor signage systems exposed to grid fluctuations. IC Role / Device Role / Timing Role: Shunt regulator connected between driver input and ground, conducting excess current when input exceeds 68 V. Use Value: Prevents driver IC latch-up or gate oxide damage with <0.25 μA leakage at 51.7 V, minimizing standby power loss. |
Use Scenario: Providing traceable 68 V calibration reference in portable multimeters and benchtop power supplies requiring stable DC references. IC Role / Device Role / Timing Role: Precision voltage standard in resistor-divider networks, used to verify DMM accuracy at mid-range voltage points. Use Value: Delivers ±5% initial tolerance and <1700 Ω dynamic impedance, enabling <0.1% measurement repeatability under 1 mA test conditions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1SMB5945BT3G | Same electrical specs and SMB package; lacks SZ prefix and AEC-Q101 qualification | Not validated for automotive use; suitable only for commercial/industrial environments | Select when AEC-Q101 compliance is not required and cost sensitivity favors non-automotive grade |
| BZX84-C68LT1G | Lower power (350 mW), SOT-23 package, 68 V ±5%, higher ZZT (50 Ω typical), no AEC-Q101 rating | Limited to low-power signal-level clamping; insufficient for 3 W continuous dissipation | Choose only for space-constrained, low-current bias networks - not a functional replacement for power regulation |
Compared with SZ1SMB5945BT3G, 1SMB5945BT3G offers identical regulation performance but omits automotive qualification, while BZX84-C68LT1G trades power handling and thermal robustness for miniaturization - making SZ1SMB5945BT3G the sole option for AEC-Q101-compliant 3 W Zener regulation at 68 V.
Availability
SZ1SMB5945BT3G is available at Aetrix Electronics and suitable for automotive power management, industrial overvoltage protection, and test equipment voltage reference applications requiring stable component supply, long-term lifecycle support, and AEC-Q101 traceability.
Supply support for SZ1SMB5945BT3G 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 is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
The SZ1SMB59xxT3G series is part of onsemi's automotive-qualified Zener portfolio, engineered specifically for reliable voltage regulation and transient suppression in harsh-environment vehicle electronics.
FAQ
What is the zener voltage tolerance for SZ1SMB5945BT3G?
The SZ1SMB5945BT3G has a nominal zener voltage of 68 V with a tolerance of ±5%, meaning the actual measured VZ falls between 64.6 V and 71.4 V when tested at IZT = 5.5 mA and TL = 30°C. This tolerance is confirmed in the Electrical Characteristics table on page 3 of the onsemi datasheet and applies to all devices in the SZ1SMB59xxT3G series.
Is SZ1SMB5945BT3G suitable for automotive applications?
Yes, SZ1SMB5945BT3G is AEC-Q101 qualified and PPAP capable, with operating temperature range from -65°C to +150°C and validation for thermal cycling, humidity, and mechanical shock. The "SZ" prefix explicitly denotes automotive-grade manufacturing controls and site-specific change management - making SZ1SMB5945BT3G appropriate for engine control units, body electronics, and ADAS power supplies.
What is the maximum surge power rating for SZ1SMB5945BT3G?
SZ1SMB5945BT3G supports up to 100 W peak nonrepetitive surge power for pulse widths ≤10 ms, as shown in Figure 2 of the onsemi datasheet. This rating assumes TJ = 25°C prior to the pulse and applies to rectangular waveforms - enabling robust transient suppression in 48 V industrial bus and automotive load-dump scenarios.
How does the thermal resistance of SZ1SMB5945BT3G affect its power handling?
SZ1SMB5945BT3G has RJA = 226 °C/W and RJL = 40 °C/W. At TA = 25°C, its 3.0 W rating derates linearly above 75°C ambient, limiting usable power to ~1.5 W at 100°C. For sustained operation, thermal design must prioritize lead-to-board conduction (via RJL path) using copper pour and multiple vias - otherwise junction temperature exceeds 150°C and risks parametric shift or failure.
What is the reverse leakage current specification for SZ1SMB5945BT3G?
SZ1SMB5945BT3G specifies IR ≤ 0.25 μA at VR = 51.7 V (80% of nominal VZ), measured at TL = 30°C. This ultra-low leakage ensures minimal current draw in high-impedance feedback dividers and battery-backed circuits - critical for maintaining accuracy in precision voltage references and reducing quiescent power in always-on systems.
SZ1SMB5945BT3G Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-214AA, SMB
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 68 V
- Tolerance:
- ±5%
- Power - Max:
- 3 W
- Impedance (Max) (Zzt):
- 120 Ohms
- Current - Reverse Leakage @ Vr:
- 1 µA @ 51.7 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.5 V @ 200 mA
- Operating Temperature:
- -65°C ~ 150°C
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMB
SZ1SMB5945BT3G FAQ
1.How can I place an order for SZ1SMB5945BT3G through Aetrix?
Please submit a Request for Quotation (RFQ) for SZ1SMB5945BT3G 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 SZ1SMB5945BT3G reliable?
The price and inventory of SZ1SMB5945BT3G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SZ1SMB5945BT3G is usually 5 days.
3.What payment methods are accepted for SZ1SMB5945BT3G?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SZ1SMB5945BT3G transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SZ1SMB5945BT3G?
SZ1SMB5945BT3G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SZ1SMB5945BT3G 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 SZ1SMB5945BT3G?
For technical support, including SZ1SMB5945BT3G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SZ1SMB5945BT3G requirements.
6.How does Aetrix verify that SZ1SMB5945BT3G is sourced from the original manufacturer or authorized distributors?
All SZ1SMB5945BT3G 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 SZ1SMB5945BT3G meets industry standards.
7.What is the process for return or replacement of SZ1SMB5945BT3G?
All SZ1SMB5945BT3G units undergo pre-shipment inspection (PSI). If there is an issue with SZ1SMB5945BT3G, 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 SZ1SMB5945BT3G part is unused and in its original packaging.
Return procedure for SZ1SMB5945BT3G:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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