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Microchip Technology 1N4494US/TR
- Part No.:
- 1N4494US/TR
- Manufacturer:
- Microchip Technology
- Category:
- Single Zener Diodes
- Package:
- SQ-MELF, A
- Datasheet:
-
1N4494US/TR.pdf
- Description:
- DIODE ZENER 160V 1.5W D5A
- Quantity:
- Payment:
- Shipping:
Inventory:100
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Product details
Overview
1N4494US/TR from Microsemi is a military-qualified, hermetically sealed MELF surface-mount Zener diode with nominal Zener voltage 160 V, 1.5 W power rating, ±5% tolerance, 1.6 mA test current (IZT), and 1000 Ω dynamic impedance (ZZT) at IZT. It operates from –65 °C to +175 °C and serves as a precision voltage reference in high-reliability power regulation circuits for aerospace and defense systems.
For engineers reviewing the 1N4494US/TR datasheet, 1N4494US/TR pinout, 1N4494US/TR application, or 1N4494US/TR equivalent, this page delivers verified electrical parameters, MIL-PRF-19500/406 qualification status, thermal derating behavior, package dimensions, and direct alternatives for ruggedized analog design and voltage stabilization under extreme environmental stress.
Technical Context
This device belongs to the 1N4460US–1N4496US series of voidless glass-sealed Zener diodes featuring internal Category 1 metallurgical bonds and triple-layer passivation. Its 160 V Zener voltage is stabilized across wide temperature and current ranges, with reverse leakage ≤0.25 µA at 128 V and maximum continuous Zener current of 8.9 mA.
The 1N4494US/TR uses a D-5A MELF package with tungsten slugs and tin/lead terminations, delivering 20 °C/W junction-to-end-cap thermal resistance and a thermal impedance curve per Figure 3. It is non-sensitive to ESD per MIL-STD-750 Method 1020 and inherently radiation-hardened per MicroNote 050.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 160 V nominal at 1.6 mA - defines stable regulation point for high-voltage reference applications |
| Power Dissipation (PD) | 1.5 W at 25 °C - supports robust operation in compact, conduction-cooled layouts |
| Dynamic Impedance (ZZT) | 1000 Ω at IZT = 1.6 mA - indicates moderate regulation stiffness under small-signal AC perturbation |
| Reverse Leakage (IR) | ≤0.25 µA at VR = 128 V - ensures minimal standby current in high-impedance bias networks |
| Junction Temperature Range | –65 °C to +175 °C - enables deployment in extended-temperature avionics and downhole electronics |
| Thermal Resistance (RθJEC) | 20 °C/W - allows accurate end-cap temperature estimation for thermal margining |
| Package Type | D-5A MELF - provides hermetic reliability and mechanical robustness for shock/vibration environments |
Pinout & Package
The 1N4494US/TR is a two-terminal Zener diode in the D-5A MELF (Metal Electrode Leadless Face) package. Cathode is marked by a single band on the glass body; no polarity marking on anode.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / low-side connection | Connected to circuit ground or lower potential node during Zener operation |
| Cathode | Zener breakdown terminal / high-side connection | Banded end; connected to unregulated input rail to clamp voltage at 160 V |
Key Features
| Feature | Design Value |
|---|---|
| Voidless hermetic glass seal | Prevents moisture ingress and long-term parameter drift in humid or corrosive atmospheres |
| Category 1 metallurgical bond | Ensures mechanical integrity and thermal cycling reliability over >1000 cycles between –65 °C and +175 °C |
| Triple-layer passivation | Suppresses surface leakage paths and enhances stability under high humidity and ionizing radiation |
| MIL-PRF-19500/406 qualification | Validated performance across JAN, JANTX, JANTXV, and JANS reliability levels for mission-critical use |
| Radiation hardness | Inherent tolerance to total ionizing dose (TID) per Microsemi MicroNote 050 - suitable for space-qualified designs |
Applications
| Aerospace Power Regulation | Defense System Reference |
|---|---|
Use Scenario: Stabilizing auxiliary supply rails in satellite power management units where voltage transients must be clamped without failure. IC Role / Device Role / Timing Role: Zener diode operating in reverse breakdown to provide fixed 160 V reference for overvoltage protection circuitry. Use Value: Hermetic seal and radiation hardness ensure uninterrupted regulation over 15+ year orbital missions. | Use Scenario: Precision voltage reference in missile guidance inertial measurement unit (IMU) bias supplies exposed to wide thermal excursions. IC Role / Device Role / Timing Role: High-stability Zener element maintaining calibration accuracy across –55 °C to +125 °C ambient. Use Value: <1000 Ω dynamic impedance and <0.25 µA leakage preserve reference integrity under low-current bias conditions. |
| Industrial High-Voltage Monitoring | Nuclear Instrumentation |
Use Scenario: Overvoltage detection in 150–200 V DC industrial motor drives where transient suppression must survive repeated surge events. IC Role / Device Role / Timing Role: Clamping diode absorbing energy during IGBT switching spikes while maintaining tight voltage threshold. Use Value: 1.5 W steady-state rating and 8.9 mA IZM support reliable surge handling without thermal runaway. | Use Scenario: Bias voltage generation for radiation detector photomultiplier tubes requiring ultra-low leakage and long-term drift stability. IC Role / Device Role / Timing Role: Low-noise, low-drift Zener source supplying high-impedance anode chain in scintillation counters. Use Value: Triple-layer passivation and voidless construction minimize dark current increase over decades of field operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4494US | Same electrical specs and package; differs only in packaging format (bulk vs. tape-and-reel) | No functional difference; TR suffix denotes EIA-481-B tape-and-reel delivery | Select 1N4494US/TR when automated SMT placement is required |
| 1N4494 | Identical Zener voltage, power, and tolerance; lacks US suffix indicating hermetic MELF construction - uses DO-41 axial package | Not suitable for high-vibration or hermetic system integration; limited thermal performance due to higher RθJA | Choose 1N4494 only for cost-sensitive commercial prototypes where MIL-spec reliability is not mandated |
Compared with 1N4494US/TR, the 1N4494US offers identical performance in bulk form but requires manual or tray-based placement, while the legacy 1N4494 sacrifices hermeticity and thermal robustness for lower cost and through-hole compatibility - making the TR variant optimal for automated, high-reliability production.
Availability
1N4494US/TR is available at Aetrix Electronics and suitable for aerospace power regulation, defense system reference, and industrial high-voltage monitoring requiring stable component supply, full traceability, and long-term lifecycle support.
Supply support for 1N4494US/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 analog and mixed-signal components for aerospace, defense, and industrial markets.
The 1N4494US/TR belongs to Microsemi's military-qualified Zener diode product line, engineered specifically for voltage regulation in mission-critical systems where failure is not an option - emphasizing hermetic sealing, radiation tolerance, and extended temperature operation.
FAQ
What is the Zener voltage tolerance for the 1N4494US/TR?
The 1N4494US/TR has a nominal Zener voltage of 160 V with a standard tolerance of ±5%, as specified in the Electrical Characteristics table on page 3 of T4-LDS-0183-1. Tighter tolerances (±2% or ±1%) are available under different suffixes (C or D), but the TR-suffixed part defaults to the 5% grade unless otherwise ordered.
Is the 1N4494US/TR RoHS compliant?
The 1N4494US/TR is not RoHS compliant by default; it uses traditional tin/lead (Sn/Pb) terminations per MIL-PRF-19500/406 requirements. RoHS-compliant matte tin terminations are available only on commercial-grade versions (no JAN/JANTX/JANTXV/JANS suffix), and the TR designation does not imply RoHS compliance.
What is the maximum reverse leakage current for the 1N4494US/TR?
The 1N4494US/TR exhibits a maximum reverse leakage current (IR) of 0.25 µA at VR = 128 V (80% of nominal VZ), as confirmed in the Electrical Characteristics table. This low leakage supports stable biasing in high-impedance reference networks and radiation-tolerant instrumentation.
Does the 1N4494US/TR require derating above 25 °C?
Yes - the 1N4494US/TR must be derated linearly above 25 °C ambient per the Temperature-Power Derating Curve (Figure 2). At 100 °C case temperature, its power dissipation drops to approximately 0.75 W, and it reaches zero derated power at 175 °C, consistent with its rated junction temperature range.
What package type does the 1N4494US/TR use, and what are its key mechanical features?
The 1N4494US/TR uses the D-5A MELF package: a cylindrical, hermetically sealed voidless glass body with tungsten slugs and tin/lead terminations. Key dimensions include BD = 0.091–0.103 inch (2.31–2.62 mm) diameter and BL = 0.168–0.200 inch (4.28–5.08 mm) length, per Package Dimensions on page 6.
1N4494US/TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- SQ-MELF, A
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 160 V
- Tolerance:
- ±5%
- Power - Max:
- 1.5 W
- Impedance (Max) (Zzt):
- 1000 Ohms
- Current - Reverse Leakage @ Vr:
- 250 nA @ 128 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.5 V @ 1 A
- Operating Temperature:
- -65°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- D-5A
1N4494US/TR FAQ
1.How can I place an order for 1N4494US/TR through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N4494US/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 1N4494US/TR reliable?
The price and inventory of 1N4494US/TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N4494US/TR is usually 5 days.
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1N4494US/TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N4494US/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 1N4494US/TR?
For technical support, including 1N4494US/TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N4494US/TR requirements.
6.How does Aetrix verify that 1N4494US/TR is sourced from the original manufacturer or authorized distributors?
All 1N4494US/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 1N4494US/TR meets industry standards.
7.What is the process for return or replacement of 1N4494US/TR?
All 1N4494US/TR units undergo pre-shipment inspection (PSI). If there is an issue with 1N4494US/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 1N4494US/TR part is unused and in its original packaging.
Return procedure for 1N4494US/TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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