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onsemi SZ1SMB5946BT3G
- Part No.:
- SZ1SMB5946BT3G
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SZ1SMB5946BT3G.pdf
- Description:
- DIODE ZENER 75V 3W SMB
- Quantity:
- Payment:
- Shipping:
Inventory:4,969
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Product details
Overview
SZ1SMB5946BT3G from onsemi is a 3 W surface-mount Zener diode with nominal zener voltage of 75 V, ±5% tolerance, 5 Ω maximum zener impedance at 140 mA test current, and 0.25 μA reverse leakage current at 56 V, used for precision voltage regulation and overvoltage protection in automotive power supplies and industrial DC-DC converters.
For engineers reviewing the SZ1SMB5946BT3G datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage stability across temperature, low dynamic impedance at rated current, AEC-Q101 qualification for automotive use, and SMB package thermal performance under sustained 3 W dissipation at lead temperature ≤75°C.
Technical Context
This device operates as a two-terminal voltage reference diode, conducting in reverse breakdown to clamp voltage at its specified VZ. Its 75 V nominal zener voltage falls within the high-voltage segment (≥68 V) of the 1SMB59xxBT3G family, where temperature coefficient shifts from negative to positive and dynamic impedance increases due to higher depletion region resistance.
The SMB package (Case 403A) enables top-side or bottom-side PCB mounting with modified L-bend leads for enhanced solder joint reliability. Thermal resistance from junction-to-lead is 40°C/W, allowing 3.0 W steady-state dissipation at TL = 75°C - critical for compact automotive modules where heatsinking is limited.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal Zener Voltage | 75 V ±5% - defines precise clamping threshold for 60–90 V rail protection circuits |
| Zener Test Current | 140 mA - operating point where VZ and ZZT are specified; supports stable regulation under moderate load |
| Max Zener Impedance | 5 Ω @ 140 mA - ensures minimal voltage deviation during transient current changes in feedback loops |
| Reverse Leakage Current | 0.25 μA @ 56 V - guarantees negligible standby power loss in always-on automotive systems |
| Power Dissipation | 3.0 W @ TL = 75°C - enables robust overvoltage suppression without external heatsink in space-constrained layouts |
| Thermal Resistance J-to-L | 40°C/W - allows direct thermal coupling to copper pour or metal-core PCB for thermal management |
| AEC-Q101 Qualified | Yes - validated for automotive applications including engine control units and body electronics |
Pinout & Package
Package: SMB (Case 403A), surface-mount plastic package with cathode polarity band, Pb-free, UL 94 V-0 rated, 2.30 mm nominal width, 4.32 mm nominal length, 1.02 mm nominal height.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Reference ground node | Connected to system ground or lower-potential rail; establishes reference for reverse-biased operation |
| Cathode | Zener breakdown terminal / Regulated output node | Connected to protected node; maintains 75 V relative to anode during overvoltage events |
Key Features
| Feature | Design Value |
|---|---|
| ESD robustness | Class 3 (>16 kV HBM) - withstands handling and assembly ESD without parameter shift or failure |
| Flat handling surface | Ensures accurate pick-and-place placement and coplanarity on fine-pitch PCBs |
| Polarity band marking | Visible cathode indicator aligned with industry-standard orientation for automated optical inspection |
| Modified L-bend leads | Increases solder contact area by >30% vs. standard gull-wing, improving mechanical reliability in thermal cycling |
| Pb-free construction | RoHS-compliant and compatible with lead-free reflow profiles up to 260°C for 10 s |
Applications
| Automotive Engine Control Unit (ECU) | Industrial DC-DC Converter Feedback |
|---|---|
Use Scenario: Clamping transient spikes on 12 V battery-supplied microcontroller I/O lines during load dump events. IC Role / Device Role / Timing Role: Two-terminal voltage clamp protecting MCU GPIO and ADC inputs from >100 V transients. Use Value: Prevents latch-up and permanent damage while maintaining signal integrity during ISO 7637-2 Pulse 5a testing. |
Use Scenario: Providing stable reference voltage for optocoupler-based feedback in isolated 48 V to 5 V flyback converters. IC Role / Device Role / Timing Role: Precision zener reference replacing TL431 where higher voltage and simpler biasing are required. Use Value: Enables tighter output regulation (±1.5%) without auxiliary bias winding or complex compensation network. |
| Telecom Power Supply OVP | Medical Equipment Input Protection |
Use Scenario: Overvoltage protection on -48 V telecom rectifier outputs against regulator failure. IC Role / Device Role / Timing Role: Primary crowbar element triggering SCR-based shutdown when rail exceeds 55 V. Use Value: Fast response (<100 ns) and low leakage ensure no false triggering during normal ripple, while surviving repeated 100 V surges. |
Use Scenario: Input-stage surge suppression for Class II medical AC/DC adapters compliant with IEC 60601-1. IC Role / Device Role / Timing Role: Secondary-side clamping device limiting internal DC bus voltage during lightning-induced surges. Use Value: AEC-Q101 qualification provides proven reliability history for safety-critical patient-connected devices. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1SMB5946BT3G | No AEC-Q101 qualification; identical electrical specs and SMB package | Not approved for automotive production; suitable for industrial/commercial designs only | Select when automotive qualification is not required and cost sensitivity is higher |
| BZX84-C75LT1G | 300 mW rating, SOT-23 package, 75 V ±5%, 100 Ω ZZT @ 5 mA | Lower power capability limits use to signal-level clamping, not power rail protection | Choose for low-current bias networks or space-constrained PCBs where 3 W dissipation is unnecessary |
Compared with SZ1SMB5946BT3G, 1SMB5946BT3G offers identical regulation performance but lacks automotive qualification, while BZX84-C75LT1G trades power handling and thermal robustness for miniaturization - making SZ1SMB5946BT3G the sole choice for AEC-Q101-compliant 3 W high-voltage clamping.
Availability
SZ1SMB5946BT3G is available at Aetrix Electronics and suitable for automotive engine control units, industrial DC-DC converters, and telecom power supply overvoltage protection requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for SZ1SMB5946BT3G 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 management, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
SZ1SMB5946BT3G belongs to the 1SMB59xxBT3G/SZ1SMB59xxT3G series - engineered for high-reliability voltage regulation in harsh environments, with emphasis on automotive-grade robustness, thermal stability, and surge immunity.
FAQ
What is the zener voltage tolerance for SZ1SMB5946BT3G?
The SZ1SMB5946BT3G has a nominal zener voltage of 75 V with a tolerance of ±5%, meaning the actual measured VZ at 140 mA test current falls between 71.25 V and 78.75 V. This tolerance is guaranteed per onsemi's datasheet specification and applies across the full operating temperature range of −65°C to +150°C.
Is SZ1SMB5946BT3G qualified for automotive applications?
Yes, SZ1SMB5946BT3G is AEC-Q101 qualified and PPAP capable, confirming its suitability for automotive applications such as engine control units, body control modules, and ADAS power supplies. The "SZ" prefix explicitly denotes compliance with automotive-specific site and change control requirements defined in the onsemi product family.
What is the maximum power dissipation of SZ1SMB5946BT3G at ambient temperature?
SZ1SMB5946BT3G delivers 550 mW maximum steady-state power dissipation at TA = 25°C, derating linearly at 4.4 mW/°C above that temperature. For sustained operation, thermal design must account for its 226°C/W junction-to-ambient thermal resistance - making PCB copper area and airflow critical for reliable 3 W operation.
How does the zener impedance of SZ1SMB5946BT3G affect regulation accuracy?
SZ1SMB5946BT3G exhibits a maximum zener impedance of 5 Ω at its 140 mA test current, meaning a 100 mA load step induces only ~0.5 V output variation. This low dynamic impedance ensures tight voltage regulation in feedback paths and transient suppression circuits where minimal VZ drift under varying current is essential.
What packaging and marking format does SZ1SMB5946BT3G use?
SZ1SMB5946BT3G is supplied in SMB (Case 403A) plastic surface-mount package on 2,500-piece tape-and-reel. It features cathode polarity band marking and device code "946B" laser-etched on the case. The "SZ" prefix and "G" suffix confirm Pb-free construction and automotive qualification per onsemi's standardized marking convention.
SZ1SMB5946BT3G Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-214AA, SMB
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 75 V
- Tolerance:
- ±5%
- Power - Max:
- 3 W
- Impedance (Max) (Zzt):
- 140 Ohms
- Current - Reverse Leakage @ Vr:
- 1 µA @ 56 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
SZ1SMB5946BT3G FAQ
1.How can I place an order for SZ1SMB5946BT3G through Aetrix?
Please submit a Request for Quotation (RFQ) for SZ1SMB5946BT3G 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 SZ1SMB5946BT3G reliable?
The price and inventory of SZ1SMB5946BT3G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SZ1SMB5946BT3G is usually 5 days.
3.What payment methods are accepted for SZ1SMB5946BT3G?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SZ1SMB5946BT3G transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SZ1SMB5946BT3G?
SZ1SMB5946BT3G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SZ1SMB5946BT3G 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 SZ1SMB5946BT3G?
For technical support, including SZ1SMB5946BT3G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SZ1SMB5946BT3G requirements.
6.How does Aetrix verify that SZ1SMB5946BT3G is sourced from the original manufacturer or authorized distributors?
All SZ1SMB5946BT3G 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 SZ1SMB5946BT3G meets industry standards.
7.What is the process for return or replacement of SZ1SMB5946BT3G?
All SZ1SMB5946BT3G units undergo pre-shipment inspection (PSI). If there is an issue with SZ1SMB5946BT3G, 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 SZ1SMB5946BT3G part is unused and in its original packaging.
Return procedure for SZ1SMB5946BT3G:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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