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Microchip Technology 1N2818BU3/TR
- Part No.:
- 1N2818BU3/TR
- Manufacturer:
- Microchip Technology
- Category:
- Single Zener Diodes
- Package:
- 3-SMD, No Lead
- Datasheet:
-
1N2818BU3/TR.pdf
- Description:
- DIODE ZENER 20V 50W U3
- Quantity:
- Payment:
- Shipping:
Inventory:6,566
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Product details
Overview
1N2818BU3/TR from Microsemi is a 50 W, 20 V ±5% Zener diode in TO-204AD (TO-3) package with anode-to-case polarity, rated for junction temperatures from –65 °C to +175 °C and thermal resistance of 2.0 °C/W. It delivers stable voltage regulation in high-reliability power supply and reference circuits requiring MIL-PRF-19500/114 qualification.
For engineers reviewing the 1N2818BU3/TR datasheet, 1N2818BU3/TR pinout, 1N2818BU3/TR application, or 1N2818BU3/TR equivalent, this part supports precise DC voltage clamping at 20 V with 1.0 mA knee current, 2.4 Ω dynamic impedance at 890 mA test current, and 10 µA reverse leakage at 15.2 V - critical for aerospace power conditioning and industrial overvoltage protection design.
Technical Context
This device operates as a high-power, hermetically sealed Zener regulator with internal solder bond construction and welded metal case. Its anode-to-case polarity enables direct mounting to heatsinks while maintaining electrical isolation via optional insulators. The 2.0 °C/W thermal resistance allows full 50 W dissipation when case temperature is maintained ≤75 °C.
It complies with MIL-PRF-19500/114 at JANTX level (U3 suffix), supports RoHS-compliant matte-tin plating (TR suffix), and exhibits radiation hardness per Microsemi MicroNote 050. Temperature coefficient is +0.086 %/°C, ensuring predictable VZ drift across –65 °C to +175 °C operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 20 V ±5% at IZT = 890 mA - defines nominal regulation point with tight tolerance for precision reference use. |
| Max Power Dissipation | 50 W @ TC ≥ 75 °C - requires active heatsinking; derates linearly at 0.5 W/°C above 75 °C. |
| Dynamic Impedance | 2.4 Ω @ IZT = 890 mA - low impedance ensures minimal output voltage variation under load transients. |
| Reverse Leakage Current | 10 µA @ VR = 15.2 V - confirms sharp breakdown knee and low standby power loss. |
| Junction Temp Range | –65 °C to +175 °C - enables operation in extreme environments including avionics and downhole tools. |
| Thermal Resistance | 2.0 °C/W (junction-to-case) - dictates minimum heatsink thermal resistance needed to sustain 50 W. |
| Zener Test Current | 890 mA - standardized test condition ensuring consistent VZ measurement across production lots. |
Pinout & Package
Package: TO-204AD (TO-3), hermetically sealed metal can with 0.052" diameter pins, weight ≈15 g. Anode internally connected to case; both pins electrically common to anode (standard polarity). Mounting requires insulator kit for case isolation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Case (Metal Body) | Anode | Primary current path and thermal interface; must be electrically isolated from chassis unless circuit design intentionally references anode to ground. |
| Pin 1 | Anode | Internally jumpered to case; provides redundant mechanical attachment and solderable terminal for anode connection. |
| Pin 2 | Anode | Identical to Pin 1 and case - dual-pin configuration improves mechanical stability and current sharing in high-current mounting. |
Key Features
| Feature | Design Value |
|---|---|
| Hermetic metal package | Weld-sealed TO-3 construction prevents moisture ingress and ensures long-term reliability in harsh environments. |
| MIL-PRF-19500/114 qualification | JANTX-level screening (U3 suffix) includes extended life testing, thermal shock, and hermeticity validation for defense programs. |
| Anode-to-case polarity | Enables direct heatsink mounting without insulating washers when anode is system ground - simplifies thermal management. |
| Low thermal resistance | 2.0 °C/W junction-to-case allows 50 W operation with modest heatsink requirements versus plastic-packaged alternatives. |
| Radiation hardness | Inherent tolerance to total ionizing dose (TID) per MicroNote 050 - suitable for space-qualified power systems. |
Applications
| Aerospace Power Conditioning | Industrial Overvoltage Protection |
|---|---|
|
Use Scenario: Regulating auxiliary 28 VDC bus in satellite power distribution units under wide temperature and radiation exposure. IC Role / Device Role / Timing Role: Zener diode acting as shunt voltage clamp to protect downstream DC-DC converters from transient overvoltage events. Use Value: 20 V regulation with +0.086 %/°C tempco and radiation hardness maintains accuracy over mission lifetime without recalibration. |
Use Scenario: Clamping surge-induced spikes on 24 V PLC I/O modules exposed to inductive load switching. IC Role / Device Role / Timing Role: High-energy shunt regulator absorbing repetitive 50–100 W transients during relay coil de-energization. Use Value: 50 W continuous rating and 2.0 °C/W RθJC enable reliable clamping without thermal runaway under repeated stress. |
| Military Radar Power Supplies | Downhole Oilfield Instrumentation |
|
Use Scenario: Providing stable 20 V reference for analog front-end circuitry in airborne radar transceivers operating at –55 °C to +125 °C. IC Role / Device Role / Timing Role: Precision voltage reference element in feedback loop of high-stability regulated power supply. Use Value: ±5% VZ tolerance and –65 °C to +175 °C junction rating ensure reference integrity across full military temperature range. |
Use Scenario: Protecting sensor signal conditioning circuitry in borehole logging tools subjected to 175 °C ambient and gamma radiation. IC Role / Device Role / Timing Role: Primary overvoltage clamp on 18–30 V bias rails feeding MEMS pressure sensors and telemetry drivers. Use Value: Hermetic TO-3 package and radiation-hardened structure prevent parameter shift or failure in high-TID environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N2818B | No U3 (JANTX) or TR (RoHS) suffixes; commercial-grade only, no military screening. | Lacks MIL-PRF-19500/114 qualification and RoHS compliance - unsuitable for defense or regulated commercial programs. | Select 1N2818B only for cost-sensitive, non-military prototypes where full qualification is unnecessary. |
| 1N2818BR | Reverse polarity (cathode-to-case); same VZ, power, and package but inverted terminal assignment. | Requires PCB layout change: case becomes cathode, so heatsink must be biased at cathode potential - incompatible with anode-grounded designs. | Choose 1N2818BR only when system architecture mandates cathode-referenced clamping or isolated heatsink biasing. |
Compared with 1N2818B and 1N2818BR, the 1N2818BU3/TR uniquely combines JANTX-level military qualification, RoHS-compliant plating, and standard anode-to-case polarity - making it the sole option for production aerospace hardware requiring traceable, screened, and environmentally compliant 20 V Zener regulation.
Availability
1N2818BU3/TR is available at Aetrix Electronics and suitable for aerospace power conditioning, industrial overvoltage protection, military radar power supplies, and downhole oilfield instrumentation requiring stable component supply with full traceability and long-lifecycle support.
Supply support for 1N2818BU3/TR 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
Microsemi Corporation (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability, radiation-hardened, and military-qualified analog and discrete components.
The 1N2818BU3/TR belongs to Microsemi's legacy MIL-PRF-19500/114-qualified 50 W Zener family, engineered for voltage regulation in mission-critical defense, aerospace, and industrial systems where long-term stability and environmental resilience are mandatory.
FAQ
What is the Zener voltage tolerance and test current for 1N2818BU3/TR?
The 1N2818BU3/TR has a nominal Zener voltage of 20 V with ±5% tolerance (B suffix), measured at a Zener test current (IZT) of 890 mA. This test condition ensures consistent regulation performance across production lots and aligns with JEDEC registration standards for the 1N28xxB series.
Does 1N2818BU3/TR support direct mounting to a heatsink without electrical isolation?
Yes - the 1N2818BU3/TR uses standard polarity (anode-to-case), so its metal case is electrically connected to the anode. If the anode is referenced to system ground or chassis, direct heatsink mounting is permissible. Otherwise, an insulating kit must be used to prevent short circuits.
What does the 'U3' and 'TR' suffix indicate in 1N2818BU3/TR?
The 'U3' suffix denotes JANTX-level qualification per MIL-PRF-19500/114, including enhanced screening for military applications. The 'TR' suffix indicates RoHS-compliant matte-tin plating on the leads and case - required for environmentally regulated commercial programs.
What is the maximum reverse leakage current specification for 1N2818BU3/TR?
The 1N2818BU3/TR specifies a maximum reverse leakage current (IR) of 10 µA at VR = 15.2 V (76% of nominal VZ). This low leakage confirms a well-defined breakdown knee and supports stable regulation in low-power reference circuits.
How does thermal derating apply to 1N2818BU3/TR at elevated case temperatures?
The 1N2818BU3/TR delivers full 50 W only when case temperature (TC) is held at or below 75 °C. Above that, power must be reduced linearly at 0.5 W/°C - e.g., at TC = 100 °C, max allowable power is 37.5 W. This reflects its 2.0 °C/W junction-to-case thermal resistance.
1N2818BU3/TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 3-SMD, No Lead
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 20 V
- Tolerance:
- ±5%
- Power - Max:
- 50 W
- Impedance (Max) (Zzt):
- 2.4 Ohms
- Current - Reverse Leakage @ Vr:
- 10 µA @ 15.2 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.5 V @ 10 A
- Operating Temperature:
- -65°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- U3 (SMD-0.5)
1N2818BU3/TR FAQ
1.How can I place an order for 1N2818BU3/TR through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N2818BU3/TR 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 1N2818BU3/TR reliable?
The price and inventory of 1N2818BU3/TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N2818BU3/TR is usually 5 days.
3.What payment methods are accepted for 1N2818BU3/TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N2818BU3/TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1N2818BU3/TR?
1N2818BU3/TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N2818BU3/TR 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 1N2818BU3/TR?
For technical support, including 1N2818BU3/TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N2818BU3/TR requirements.
6.How does Aetrix verify that 1N2818BU3/TR is sourced from the original manufacturer or authorized distributors?
All 1N2818BU3/TR 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 1N2818BU3/TR meets industry standards.
7.What is the process for return or replacement of 1N2818BU3/TR?
All 1N2818BU3/TR units undergo pre-shipment inspection (PSI). If there is an issue with 1N2818BU3/TR, 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 1N2818BU3/TR part is unused and in its original packaging.
Return procedure for 1N2818BU3/TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1N2818BU3/TR Tags
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