My Inquiry
My Account
Microchip Technology 1N991A
- Part No.:
- 1N991A
- Manufacturer:
- Microchip Technology
- Category:
- Single Zener Diodes
- Package:
- DO-204AA, DO-7, Axial
- Datasheet:
-
1N991A.pdf
- Description:
- DIODE ZENER 180V 500MW DO7
- Quantity:
- Payment:
- Shipping:
Inventory:9,826
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
1N991A from Microsemi is a silicon 500 mW axial-leaded Zener diode in DO-35 (DO-204AH) package, rated for 180 V nominal Zener voltage at 0.25 mA test current, with ±10% tolerance (A suffix), 2.0 mA maximum DC Zener current, and +0.11 %/°C temperature coefficient. It regulates voltage in low-power reference and protection circuits across industrial temperature range.
For engineers reviewing the 1N991A datasheet, 1N991A pinout, 1N991A application, or 1N991A equivalent, this page delivers verified electrical parameters, thermal derating behavior, JEDEC-compliant packaging, and real-world substitution guidance - all specific to the 1N991A variant within the 1N957B–1N992B family.
Technical Context
The 1N991A operates as a two-terminal voltage reference device, conducting in reverse breakdown above its 180 V nominal Zener voltage with a sharp knee at IZK = 0.25 mA. Its Zener impedance is 7100 Ω at IZT and 2500 Ω at IZK, confirming stable regulation under light-load conditions.
It features a hermetically sealed glass DO-35 package with tin-lead or RoHS-compliant matte-tin plating, cathode band marking, and polarity-sensitive operation (banded end positive). Thermal resistance is 310 °C/W junction-to-ambient on FR4 with defined copper pad layout.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal Zener Voltage | 180 V ±10% - defines precise clamping threshold for overvoltage protection or reference generation |
| Zener Test Current | 0.25 mA - minimum current required to achieve specified VZ; sets lower bound for bias network design |
| Max DC Zener Current | 2.0 mA - maximum continuous reverse current before exceeding 400 mW dissipation at 75 °C lead temp |
| Zener Impedance | 7100 Ω @ IZT, 2500 Ω @ IZK - indicates voltage stability under varying load; higher values imply greater sensitivity to current changes |
| Temp Coefficient | +0.11 %/°C - quantifies drift rate; 180 V device shifts ~198 mV/°C, critical for precision references |
| Reverse Leakage | 5 μA @ 136.8 V - ensures minimal parasitic current below breakdown, preserving signal integrity in high-impedance nodes |
| Power Dissipation | 500 mW @ TL < 50 °C (3/8″ lead length) - defines thermal envelope for PCB layout and heatsinking decisions |
Pinout & Package
Package: DO-35 (DO-204AH), hermetically sealed axial-leaded glass body, cathode indicated by colored band. Tin-lead or RoHS-compliant matte-tin plating, weight 0.2 g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Non-banded lead | Connected to lower-potential node; reverse-biased during regulation |
| Cathode | Banded lead | Connected to higher-potential node; defines regulated output voltage referenced to anode |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC-registered Zener | Complies with standardized 1N991A electrical and mechanical specifications for interchangeability |
| ±10% voltage tolerance | Enables cost-effective use where tight regulation is not required, e.g., coarse overvoltage clamping |
| −65 °C to +175 °C operating range | Supports deployment in harsh environments including automotive under-hood and industrial motor controls |
| Nonsensitive to ESD | Withstands MIL-STD-750 Method 1020 testing - eliminates need for external ESD protection in many layouts |
| Minimal capacitance | Typical CJ < 2 pF (per Figure 3) - preserves high-frequency signal integrity in RF bias or fast-switching circuits |
Applications
| Industrial Power Supply Monitoring | High-Voltage Reference Generator |
|---|---|
Use Scenario: Monitoring 200 V DC bus in programmable logic controller (PLC) power modules to trigger shutdown if voltage exceeds safe limit. IC Role / Device Role / Timing Role: Zener diode acting as precision voltage threshold detector in comparator input stage. Use Value: 1N991A's 180 V rating with +0.11 %/°C TC enables reliable trip point calibration across −40 °C to +85 °C ambient. |
Use Scenario: Providing stable 180 V reference for analog-to-digital converter (ADC) scaling in high-voltage data acquisition systems. IC Role / Device Role / Timing Role: Two-terminal passive voltage reference establishing known full-scale input for 16-bit ADC front-end. Use Value: Low leakage (5 μA @ 136.8 V) minimizes loading error on high-impedance divider networks feeding the ADC. |
| Telecom Line Surge Protection | Test Equipment Calibration Circuit |
Use Scenario: Clamping transient surges on 170 V telecom line interface cards per GR-1089-CORE requirements. IC Role / Device Role / Timing Role: Primary Zener clamp absorbing energy during lightning-induced transients. Use Value: 500 mW steady-state rating and 200 mA surge capability (IZSM) allow robust handling of repetitive 10/1000 μs waveforms. |
Use Scenario: Calibrating high-voltage probe accuracy in benchtop multimeters using traceable Zener reference standards. IC Role / Device Role / Timing Role: Secondary reference standard maintained at constant temperature for periodic verification. Use Value: Hermetic DO-35 package ensures long-term parameter stability and immunity to humidity-induced drift. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N991B | Same 180 V nominal voltage but ±5% tolerance (B suffix) and 2.0 mA IZM vs. 1N991A's ±10% and 2.0 mA | Used where tighter voltage accuracy is required without changing board layout or thermal design | Select 1N991B when reference stability dominates cost sensitivity; retains identical DO-35 footprint and thermal profile |
| 1N991C | Same 180 V nominal voltage with ±2% tolerance (C suffix); otherwise identical max ratings and package | Deployed in metrology-grade instruments requiring sub-4 V total variation over temperature and life | Choose 1N991C only when system-level calibration budget permits tighter initial tolerance and lower long-term drift risk |
Compared with 1N991A, the 1N991B offers improved voltage accuracy without altering thermal or mechanical integration, while the 1N991C further reduces tolerance-driven uncertainty at higher unit cost - both maintain identical DO-35 mounting and 180 V regulation function.
Availability
1N991A is available at Aetrix Electronics and suitable for industrial power supply monitoring, high-voltage reference generation, telecom line surge protection, and test equipment calibration requiring stable component supply and long-lifecycle support.
Supply support for 1N991A 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 (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability analog, mixed-signal, and radiation-hardened components for aerospace, defense, and industrial markets.
The 1N957B–1N992B series was designed specifically for ruggedized, wide-temperature-range Zener regulation in mission-critical power and sensing applications where hermetic sealing and JEDEC compliance are mandatory.
FAQ
What is the Zener voltage tolerance for 1N991A?
The 1N991A has a nominal Zener voltage of 180 V with a ±10% tolerance, as indicated by the "A" suffix per Microsemi documentation. This means the actual measured VZ at IZT = 0.25 mA falls between 162 V and 198 V at 25 °C. The tolerance reflects manufacturing spread and is distinct from temperature-induced drift, which adds ±0.11 %/°C variation beyond the base tolerance band.
Can 1N991A be used in surface-mount designs?
No, the 1N991A is exclusively offered in the axial-leaded DO-35 (DO-204AH) glass package and is not a surface-mount device. For SMT equivalents, Microsemi lists MLL957B–MLL992B in DO-213AA (MELF) format - but those are separate part numbers with different markings, thermal profiles, and assembly requirements. Substituting 1N991A into an SMT footprint would require mechanical adaptation and invalidate thermal derating assumptions.
What is the maximum surge current rating for 1N991A?
The 1N991A has a maximum surge current (IZSM) rating of 10 mA for a 1/120 second square-wave or equivalent half-sine pulse, as specified in the Electrical Characteristics table. This value is derived from the device's ability to absorb transient energy without permanent degradation, assuming proper lead length and thermal path. Exceeding this rating risks irreversible junction damage even if average power remains within 500 mW limits.
How does temperature affect the Zener voltage of 1N991A?
The 1N991A exhibits a positive temperature coefficient of +0.11 %/°C, meaning its Zener voltage increases linearly with junction temperature. At 180 V nominal, this equates to +198 mV/°C shift. For example, a 50 °C rise from 25 °C increases VZ by ~9.9 V. This behavior is inherent to the device's silicon doping and must be factored into reference stability budgets for precision applications.
Is 1N991A RoHS compliant?
The base 1N991A part number is not RoHS compliant by default. RoHS compliance requires the "e3" suffix (e.g., 1N991Ae3), indicating annealed matte-tin plating instead of traditional tin-lead. Microsemi documentation confirms that "e3" denotes RoHS-compliant termination, and absence of this suffix implies legacy Sn/Pb finish. Always verify the full marked part number on the device body or reel label to confirm compliance status.
1N991A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- DO-204AA, DO-7, Axial
- Packaging:
- Bulk
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 180 V
- Tolerance:
- ±10%
- Power - Max:
- 500 mW
- Impedance (Max) (Zzt):
- 2200 Ohms
- Current - Reverse Leakage @ Vr:
- 5 µA @ 136.8 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.1 V @ 200 mA
- Operating Temperature:
- -65°C ~ 175°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-7
1N991A FAQ
1.How can I place an order for 1N991A through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N991A 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 1N991A reliable?
The price and inventory of 1N991A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N991A is usually 5 days.
3.What payment methods are accepted for 1N991A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N991A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1N991A?
1N991A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N991A 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 1N991A?
For technical support, including 1N991A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N991A requirements.
6.How does Aetrix verify that 1N991A is sourced from the original manufacturer or authorized distributors?
All 1N991A 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 1N991A meets industry standards.
7.What is the process for return or replacement of 1N991A?
All 1N991A units undergo pre-shipment inspection (PSI). If there is an issue with 1N991A, 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 1N991A part is unused and in its original packaging.
Return procedure for 1N991A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1N991A Tags
-
MMBZ5240B-7-F
Diodes Incorporated
-
BZT52C5V6T-7
Diodes Incorporated
-
MMSZ5231B-7-F
Diodes Incorporated
-
BZT52C15-7-F
Diodes Incorporated
-
BZX84C3V3LT1G
onsemi
-
MMSZ5245BS-7-F
Diodes Incorporated
-
MMSZ4682T1G
onsemi
-
BZT52C15S-7-F
Diodes Incorporated
-
MM5Z5V1ST1G
onsemi
-
SMAJ4744A-TP
Micro Commercial Co
-
BZT52C3V6LP-7
Diodes Incorporated
-
SMAZ12-13-F
Diodes Incorporated
Tech Hub
TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
