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Microchip Technology 1N4491US/TR
- Part No.:
- 1N4491US/TR
- Manufacturer:
- Microchip Technology
- Category:
- Single Zener Diodes
- Package:
- SQ-MELF, A
- Datasheet:
-
1N4491US/TR.pdf
- Description:
- DIODE ZENER 120V 1.5W D5A
- Quantity:
- Payment:
- Shipping:
Inventory:100
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Product details
Overview
1N4491US/TR from Microsemi is a hermetically sealed, voidless glass MELF surface-mount Zener diode rated for 1.5 W steady-state power dissipation, with a nominal Zener voltage of 120 V at 2.0 mA test current, 400 Ω dynamic impedance, and maximum reverse leakage of 0.25 µA at 96 V. It serves as a precision voltage reference in high-reliability military and aerospace power regulation circuits.
For engineers reviewing the 1N4491US/TR datasheet, 1N4491US/TR pinout, 1N4491US/TR application, or 1N4491US/TR equivalent, this part delivers MIL-PRF-19500/406 qualified voltage regulation with JANS-level reliability, thermal stability up to +175 °C junction temperature, and radiation-hardened construction suitable for critical avionics and space-grade systems.
Technical Context
This device operates in reverse breakdown mode to maintain stable output voltage across wide current (2.0 mA to 12 mA) and temperature (–65 °C to +175 °C) ranges. Its internal Category I metallurgical bond and triple-layer passivation ensure long-term parametric stability under thermal cycling and mechanical stress.
The 1N4491US/TR uses a D-5A MELF package with tungsten slugs and tin/lead terminations, achieving 20 °C/W junction-to-end-cap thermal resistance. Its Zener voltage exhibits predictable positive temperature coefficient above ~6 V, confirmed in Figure 1 of the datasheet.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal Zener Voltage (VZ) | 120 V at IZT = 2.0 mA - defines regulated output voltage under standard test conditions |
| Power Dissipation (PD) | 1.5 W @ TA = 25 °C - sets maximum continuous thermal load without derating |
| Dynamic Impedance (ZZT) | 400 Ω @ IZT = 2.0 mA - determines output voltage variation under load current changes |
| Max Reverse Leakage (IR) | 0.25 µA @ VR = 96 V - ensures minimal standby current in high-impedance bias networks |
| Junction Temperature Range | –65 °C to +175 °C - enables operation in extreme environmental conditions including space and jet engine bays |
| Zener Knee Current (IZK) | 0.05 mA - specifies minimum current needed to enter stable regulation region near breakdown threshold |
| Forward Voltage (VF) | 1.5 V @ 1.0 A - defines conduction drop when used in forward-biased protection or clamping roles |
Pinout & Package
The 1N4491US/TR is a two-terminal device in the D-5A MELF (Metal Electrode Leadless Face) package: cylindrical glass body with metallized end caps, total length 4.28–5.08 mm, diameter 2.31–2.62 mm, weight 193 mg. Cathode is marked by a single band.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / low-side reference node | Connected to circuit ground or lower potential in shunt regulator topology |
| Cathode | Zener breakdown terminal / regulated output node | Banded end; connects to unregulated input rail to sink excess current and clamp voltage |
Key Features
| Feature | Design Value |
|---|---|
| Voidless hermetic glass seal | Eliminates moisture ingress and internal delamination, ensuring >20-year parametric stability in sealed enclosures |
| Category I metallurgical bond | Provides mechanical robustness against shock/vibration per MIL-STD-883 Method 2002 |
| MIL-PRF-19500/406 qualification | Validated for JAN, JANTX, JANTXV, and JANS reliability levels - required for DoD procurement |
| Triple-layer passivation | Prevents surface leakage paths and enhances long-term reliability in high-humidity environments |
| Radiation hardness | Characterized per MicroNote 050 for total ionizing dose tolerance - suitable for low-earth orbit missions |
Applications
| Avionics Power Conditioning | Satellite Voltage Reference |
|---|---|
Use Scenario: Regulating auxiliary 120 V bus in flight control computers where failure is not tolerable. IC Role / Device Role / Timing Role: Shunt voltage reference providing stable bias for op-amp comparators and ADC references. Use Value: Maintains ±1% regulation over –55 °C to +125 °C ambient with <0.25 µA leakage, minimizing drift-induced sensor errors. | Use Scenario: Precision reference in star tracker power supply within LEO satellite payload. IC Role / Device Role / Timing Role: Primary Zener reference for DC-DC converter feedback loop under radiation exposure. Use Value: Radiation-hardened construction sustains regulation accuracy after 100 krad(Si), avoiding mission-critical voltage collapse. |
| Missile Guidance Bias Network | Nuclear Instrumentation Calibration |
Use Scenario: Establishing fixed bias points for gyro amplifier stages during high-g launch transients. IC Role / Device Role / Timing Role: High-stability Zener element in analog signal conditioning chain. Use Value: Withstands 20,000 g shock per MIL-STD-883 Method 2002 and maintains VZ within 0.5% post-shock. | Use Scenario: Calibrating high-voltage neutron detector front-end amplifiers in reactor monitoring systems. IC Role / Device Role / Timing Role: Traceable 120 V reference standard traceable to NIST via JANS-certified lot data. Use Value: Delivers certified 5% tolerance with full MIL-PRF-19500 lot documentation and burn-in test reports. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4491US | 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 1N4491US/TR for automated SMT placement; choose bulk 1N4491US for manual prototyping or low-volume hand assembly |
| 1N4491 | Non-hermetic DO-41 axial package; lacks MIL-PRF-19500 qualification and radiation hardness | Not suitable for aerospace/military use; limited to commercial industrial environments | Use only where cost sensitivity outweighs reliability requirements and environmental stress is minimal |
Compared with 1N4491US/TR, the bulk 1N4491US offers identical performance but no reel logistics; the legacy 1N4491 lacks hermetic sealing and qualification, making it unsuitable for high-reliability deployments despite matching nominal voltage.
Availability
1N4491US/TR is available at Aetrix Electronics and suitable for avionics power conditioning, satellite voltage reference, missile guidance bias networks, and nuclear instrumentation calibration requiring stable component supply across extended product lifecycles.
Supply support for 1N4491US/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 defense, aerospace, and industrial markets.
The 1N4491US/TR belongs to Microsemi's military-qualified Zener diode family designed specifically for MIL-PRF-19500/406-compliant shunt regulation in safety-critical systems where parametric drift or catastrophic failure is unacceptable.
FAQ
What is the Zener voltage tolerance for 1N4491US/TR?
The 1N4491US/TR has a nominal Zener voltage of 120 V with a standard tolerance of ±5%, as defined in the Electrical Characteristics table on page 3 of T4-LDS-0183-1. No suffix indicates 5% tolerance; tighter 1% or 2% versions use D or C suffixes respectively. The 1N4491US/TR itself carries no tolerance suffix and therefore conforms to ±5%.
Is 1N4491US/TR RoHS compliant?
The 1N4491US/TR is available in both RoHS-compliant and non-RoHS versions. Per the nomenclature table, the "e3" suffix denotes RoHS compliance, which applies only to commercial-grade units. Since 1N4491US/TR lacks the e3 suffix and is qualified to MIL-PRF-19500/406, it uses standard tin/lead terminations and is not RoHS compliant.
What is the maximum surge current rating for 1N4491US/TR?
The 1N4491US/TR has a non-repetitive peak Zener surge current (IZSM) of 0.12 A for an 8.3 ms square wave, as specified in the Electrical Characteristics table. This value reflects its ability to absorb transient energy without degradation, critical for protecting downstream circuitry during voltage spikes in harsh environments.
Does 1N4491US/TR require derating above 25 °C ambient?
Yes, the 1N4491US/TR must be derated linearly above 25 °C ambient temperature. Per Figure 2 (Temperature-Power Derating Curve), its power dissipation decreases from 1.5 W at 25 °C to zero at approximately 150 °C case temperature. Derating slope is ~12 mW/°C, consistent with its 20 °C/W thermal resistance.
What does the "TR" suffix mean in 1N4491US/TR?
The "TR" suffix in 1N4491US/TR indicates tape-and-reel packaging per EIA-481-B standard, enabling automated surface-mount assembly. It does not alter electrical specifications, qualification level, or reliability - the device remains identical to 1N4491US in all technical respects, differing only in delivery format for SMT line compatibility.
1N4491US/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):
- 120 V
- Tolerance:
- ±5%
- Power - Max:
- 1.5 W
- Impedance (Max) (Zzt):
- 400 Ohms
- Current - Reverse Leakage @ Vr:
- 250 nA @ 96 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
1N4491US/TR FAQ
1.How can I place an order for 1N4491US/TR through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N4491US/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 1N4491US/TR reliable?
The price and inventory of 1N4491US/TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N4491US/TR is usually 5 days.
3.What payment methods are accepted for 1N4491US/TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N4491US/TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1N4491US/TR?
1N4491US/TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N4491US/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 1N4491US/TR?
For technical support, including 1N4491US/TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N4491US/TR requirements.
6.How does Aetrix verify that 1N4491US/TR is sourced from the original manufacturer or authorized distributors?
All 1N4491US/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 1N4491US/TR meets industry standards.
7.What is the process for return or replacement of 1N4491US/TR?
All 1N4491US/TR units undergo pre-shipment inspection (PSI). If there is an issue with 1N4491US/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 1N4491US/TR part is unused and in its original packaging.
Return procedure for 1N4491US/TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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