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onsemi 1SMB5945BT3
- Part No.:
- 1SMB5945BT3
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
1SMB5945BT3.pdf
- Description:
- DIODE ZENER 68V 3W SMB
- Quantity:
- Payment:
- Shipping:
Inventory:2,064
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Product details
Overview
1SMB5945BT3 from onsemi is a 3 W surface-mount Zener diode with nominal zener voltage of 68 V, maximum zener impedance of 5.5 Ω at 120 mA test current, and reverse leakage current ≤0.25 μA at 51.7 V. It features AEC-Q101 qualification, ESD rating >16 kV (HBM), and SMB (Case 403A) plastic package for automotive and industrial voltage regulation.
For engineers reviewing the 1SMB5945BT3 datasheet, pinout, applications, or equivalent options, key selection criteria include its 68 V ±5% zener tolerance, 3 W power dissipation at TL = 75°C, thermal resistance of 40 °C/W junction-to-lead, and Pb-free SMB package compatibility with automated SMT assembly.
Technical Context
This device operates as a precision DC voltage reference and overvoltage clamp in power supply feedback loops and protection circuits. Its 68 V nominal zener voltage is specified at IZT = 120 mA with ZZT ≤ 5.5 Ω, and it maintains stable regulation across −65°C to +150°C operating temperature range.
The 1SMB5945BT3 uses a planar epitaxial construction with cathode polarity indicated by a band, and achieves 226 °C/W junction-to-ambient thermal resistance on FR-4 board. Derating begins above 25°C ambient or 75°C lead temperature, supporting robust thermal management in compact layouts.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 68 V nominal (64.6–71.4 V, ±5% tolerance) - sets precise clamping/reference level in feedback or protection paths |
| Zener Test Current (IZT) | 120 mA - defines operating point where VZ and dynamic impedance are guaranteed |
| Zener Impedance (ZZT) | ≤5.5 Ω @ IZT - ensures low AC impedance for stable regulation under varying load conditions |
| Max Power Dissipation (PD) | 3.0 W @ TL = 75°C - supports high-energy transient suppression without derating in thermally anchored designs |
| Reverse Leakage (IR) | ≤0.25 μA @ VR = 51.7 V - enables low-quiescent-current operation in battery-backed or standby circuits |
| Junction-to-Lead RθJL | 40 °C/W - allows direct thermal coupling to PCB copper for efficient heat transfer in high-reliability applications |
| ESD Rating | Class 3 (>16 kV HBM) - provides robust handling and system-level ESD immunity without external protection |
Pinout & Package
Package: SMB (Case 403A), surface-mount plastic package with modified L-bend leads, cathode indicated by polarity band, UL 94 V-0 flammability rating, and Pb-free construction.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Zener cathode reference node | Connected to lower-potential side of regulated circuit; forms reference ground return path in shunt regulator topologies |
| Cathode | Zener breakdown terminal / Voltage clamp input | Connected to higher-potential rail being regulated or protected; carries full surge current during overvoltage events |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive under-hood applications including engine control modules and body electronics |
| 3 W steady-state power | Enables single-device transient suppression up to 100 W peak (per Figure 2) without external heatsinking |
| ±5% zener tolerance | Reduces need for post-assembly trimming in production, improving yield in voltage-critical feedback networks |
| Flat handling surface | Ensures consistent coplanarity and placement accuracy during high-speed pick-and-place assembly |
| Top/bottom board mounting | Supports dual-side PCB routing and space-constrained layouts where component height must be minimized |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC Analog Input Protection |
|---|---|
Use Scenario: Clamping 12 V/24 V supply rails against load-dump transients in engine management systems. IC Role / Device Role / Timing Role: Shunt voltage regulator and overvoltage protector placed across microcontroller power pins. Use Value: Withstands 100 W nonrepetitive surges (Figure 2) and maintains <0.25 μA leakage at 51.7 V, preserving low-power sleep modes. |
Use Scenario: Protecting 4–20 mA current loop receiver inputs from field-induced surges in factory automation. IC Role / Device Role / Timing Role: Precision voltage clamp referenced to isolated analog ground, limiting input to safe levels before ADC front-end. Use Value: 5.5 Ω dynamic impedance ensures minimal voltage deviation during fast transients, preserving signal integrity in 16-bit measurement systems. |
| DC-DC Converter Feedback Network | Medical Equipment Power Supply Monitoring |
Use Scenario: Providing stable 68 V reference for optocoupler-based feedback in isolated flyback converters. IC Role / Device Role / Timing Role: Zener reference element setting secondary-side regulation threshold in isolated power supplies. Use Value: ±5% tolerance and 68 V nominal value enable accurate output voltage setpoint without calibration, reducing BOM count. |
Use Scenario: Monitoring high-voltage auxiliary rails (e.g., 60–70 V) in diagnostic imaging power subsystems. IC Role / Device Role / Timing Role: Fail-safe voltage supervisor that triggers shutdown if rail exceeds 71.4 V (max VZ). Use Value: AEC-Q101 qualification and −65°C to +150°C operating range ensure reliability in thermally demanding medical enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N5945BRLG | Same 68 V nominal zener voltage but DO-41 through-hole package; 1.5 W power rating; no AEC-Q101 qualification | Not suitable for SMT production or automotive environments; limited to prototyping or low-volume through-hole designs | Select only when legacy through-hole layout or manual assembly is required |
| SZ1SMB5945BT3G | Identical electrical specs and SMB package; "SZ" prefix denotes AEC-Q101 compliance and PPAP capability; same Pb-free construction | Designed specifically for automotive OEM programs requiring full traceability and process validation | Preferred for Tier 1 automotive supply chains where PPAP documentation is mandatory |
Compared with 1SMB5945BT3, 1N5945BRLG lacks SMT compatibility and automotive qualification, while SZ1SMB5945BT3G adds formal PPAP support without altering electrical performance-making it the drop-in choice for certified automotive deployments.
Availability
1SMB5945BT3 is available at Aetrix Electronics and suitable for automotive engine control units, industrial programmable logic controllers, and medical power supply monitoring requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.
Supply support for 1SMB5945BT3 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 IoT applications.
The 1SMB59xxBT3 series is part of onsemi's high-reliability Zener regulator portfolio, engineered for stable voltage reference and transient suppression in harsh-environment applications where precision, ruggedness, and AEC-Q101 compliance are essential.
FAQ
What is the nominal zener voltage and tolerance of the 1SMB5945BT3?
The 1SMB5945BT3 has a nominal zener voltage of 68 V with a tolerance of ±5%, meaning the actual measured voltage falls between 64.6 V and 71.4 V at IZT = 120 mA and TL = 30°C. This tolerance is confirmed in the Electrical Characteristics table on page 3 of the official datasheet and applies directly to the 1SMB5945BT3 device marking "945B".
Is the 1SMB5945BT3 suitable for automotive applications?
Yes, the 1SMB5945BT3 is AEC-Q101 qualified and PPAP capable, as explicitly stated in the Features section of the datasheet. While the "SZ" prefix variants (e.g., SZ1SMB5945BT3G) emphasize automotive-specific change controls, the 1SMB5945BT3 itself meets the stress-test requirements defined in AEC-Q101 Rev D for Zener diodes and is approved for use in engine control, body electronics, and chassis systems.
What is the maximum surge power rating of the 1SMB5945BT3?
The 1SMB5945BT3 supports up to 100 W peak nonrepetitive surge power for pulse widths ≤10 ms, as shown in Figure 2 ("Maximum Surge Power") of the datasheet. This rating assumes TJ = 25°C prior to the pulse and applies to rectangular waveforms; actual clamping performance depends on PCB copper area and thermal interface design.
Does the 1SMB5945BT3 have Pb-free packaging?
Yes, the "G" suffix in the ordering code (1SMB5945BT3G) indicates Pb-free packaging, and the base part number 1SMB5945BT3 is also supplied in Pb-free form per the datasheet's "ORDERING INFORMATION" table. Both versions comply with JEDEC J-STD-020 moisture sensitivity level 1 and RoHS Directive 2011/65/EU.
What is the thermal resistance from junction to ambient for the 1SMB5945BT3?
The 1SMB5945BT3 has a thermal resistance from junction to ambient (RθJA) of 226 °C/W when mounted on an FR-4 board using the recommended footprint. This value is specified in the "MAXIMUM RATINGS" table and assumes zero airflow and standard 1 oz copper; actual performance improves with added copper pour or thermal vias.
1SMB5945BT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-214AA, SMB
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMB
1SMB5945BT3 FAQ
1.How can I place an order for 1SMB5945BT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMB5945BT3 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 1SMB5945BT3 reliable?
The price and inventory of 1SMB5945BT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMB5945BT3 is usually 5 days.
3.What payment methods are accepted for 1SMB5945BT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMB5945BT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMB5945BT3?
1SMB5945BT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMB5945BT3 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 1SMB5945BT3?
For technical support, including 1SMB5945BT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMB5945BT3 requirements.
6.How does Aetrix verify that 1SMB5945BT3 is sourced from the original manufacturer or authorized distributors?
All 1SMB5945BT3 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 1SMB5945BT3 meets industry standards.
7.What is the process for return or replacement of 1SMB5945BT3?
All 1SMB5945BT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMB5945BT3, 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 1SMB5945BT3 part is unused and in its original packaging.
Return procedure for 1SMB5945BT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1SMB5945BT3 Tags
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