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Microchip Technology 1N991B
- Part No.:
- 1N991B
- Manufacturer:
- Microchip Technology
- Category:
- Single Zener Diodes
- Package:
- DO-204AA, DO-7, Axial
- Datasheet:
-
1N991B.pdf
- Description:
- DIODE ZENER 180V 500MW DO7
- Quantity:
- Payment:
- Shipping:
Inventory:3,498
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Product details
Overview
1N991B 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 0.68 mA test current, with ±5% tolerance (B suffix), 2200 Ω maximum Zener impedance at IZT, and +0.11 %/°C temperature coefficient. It regulates voltage in low-power reference and protection circuits across industrial temperature range.
For engineers reviewing the 1N991B datasheet, 1N991B pinout, 1N991B application, or 1N991B equivalent, key selection factors include its 180 V Zener voltage, 0.68 mA test current, 2200 Ω dynamic impedance, -65°C to +175°C operating temperature, and DO-35 glass axial-leaded package compatibility with through-hole PCB assembly.
Technical Context
The 1N991B operates as a reverse-biased voltage reference device, maintaining stable 180 V regulation over a broad current range (IZK = 0.25 mA, IZM = 2.0 mA) and temperature extremes (-65°C to +175°C). Its Zener impedance of 2200 Ω at 0.68 mA reflects knee sharpness and stability under varying load conditions.
Designed for JEDEC-standard compliance, it features tin-lead or RoHS-compliant matte-tin plating, cathode band polarity marking, and hermetically sealed glass DO-35 construction. Thermal resistance is 250 °C/W junction-to-lead (3/8" lead length) and 310 °C/W junction-to-ambient on FR4 board with defined copper pad geometry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal Zener Voltage | 180 V - precise regulation point for high-voltage reference or clamping applications |
| Zener Test Current | 0.68 mA - minimum current required to achieve specified 180 V regulation |
| Zener Impedance | 2200 Ω @ IZT - indicates voltage stability under small-signal AC variations |
| Max DC Zener Current | 2.0 mA - maximum continuous current before exceeding 400 mW dissipation at 75°C lead temp |
| Temp Coefficient | +0.11 %/°C - predictable positive drift enables compensation in precision references |
| Reverse Leakage | 5 μA @ 136.8 V - low leakage ensures minimal error in high-impedance bias networks |
| Power Dissipation | 500 mW @ TL < 50°C - derates linearly above 50°C per Figure 1 power curve |
Pinout & Package
Package: DO-35 (DO-204AH), hermetically sealed axial-leaded glass body, 0.2 g weight, cathode indicated by colored band. Tin-lead or RoHS-compliant matte-tin plating, solderable per MIL-STD-750 Method 2026.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Non-banded end | Connected to lower potential node during Zener operation; forward voltage ≤1.3 V @ 200 mA |
| Cathode | Banded end | Connected to higher potential node; Zener breakdown occurs when cathode is ≥180 V above anode |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC-registered Zener series | Ensures standardized electrical behavior and interchangeability across qualified suppliers |
| ±5% Zener voltage tolerance (B suffix) | Meets general-purpose regulation accuracy without requiring tight-tolerance sourcing |
| -65°C to +175°C operating range | Supports deployment in aerospace, downhole, and high-reliability industrial environments |
| Nonsensitive to ESD (MIL-STD-750 Method 1020) | Eliminates need for handling precautions beyond standard static-safe protocols |
| Inherently radiation-hardened | Validated per Microsemi MicroNote 050 for use in radiation-exposed systems |
Applications
| High-Voltage Power Supply Reference | Overvoltage Protection Clamp |
|---|---|
Use Scenario: Stabilizing feedback node in 200 V DC-DC converter output stage. IC Role / Device Role / Timing Role: Zener diode providing fixed 180 V reference for error amplifier comparison. Use Value: Maintains ±5% output regulation despite line/load transients and temperature shifts from -40°C to +125°C ambient. |
Use Scenario: Clamping transient spikes on 150 V bus in motor drive gate driver circuit. IC Role / Device Role / Timing Role: Shunt protector diverting surge energy above 180 V to ground. Use Value: Limits peak voltage to 180 V + IZSM × ZZT, preventing MOSFET gate oxide failure during 1/120 sec surges. |
| Precision Analog Sensor Biasing | Legacy Equipment Voltage Calibration |
Use Scenario: Generating stable bias voltage for high-impedance photodiode amplifier in spectroscopy module. IC Role / Device Role / Timing Role: Low-leakage (5 μA @ 136.8 V) Zener reference establishing 180 V common-mode level. Use Value: Enables sub-0.1% gain stability over 10-year field life due to radiation hardness and thermal coefficient predictability. |
Use Scenario: Replacing obsolete 180 V Zener in military-grade test equipment calibration circuitry. IC Role / Device Role / Timing Role: Direct-fit DO-35 replacement maintaining original footprint and electrical specs. Use Value: Eliminates redesign effort while meeting MIL-STD-750 qualification and -65°C to +175°C storage requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N991A | ±10% Zener voltage tolerance vs. 1N991B's ±5%; otherwise identical DO-35 package and 180 V nominal rating | Suitable where cost sensitivity outweighs regulation accuracy; not recommended for closed-loop feedback | Select 1N991A only if system-level tolerance budget allows ±10% deviation at 180 V |
| MMBZ5267B | Surface-mount SOT-23 package, 180 V nominal, ±5%, but rated at 225 mW (vs. 500 mW) and 1.5 Ω ZZT @ 1.0 mA | Used in space-constrained PCBs; requires layout change and derating for equivalent power handling | Choose MMBZ5267B only when board area is critical and thermal management supports lower power dissipation |
Compared with 1N991A and MMBZ5267B, the 1N991B delivers optimal balance of accuracy, power capability, and legacy compatibility-its 500 mW rating and DO-35 form factor make it uniquely suited for through-hole industrial and defense systems where reliability and thermal margin are prioritized over miniaturization.
Availability
1N991B is available at Aetrix Electronics and suitable for high-voltage reference design, overvoltage clamp circuits, and legacy equipment repair requiring stable component supply and long-term obsolescence support.
Supply support for 1N991B 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 and mixed-signal components for aerospace, defense, and industrial markets.
The 1N991B belongs to Microsemi's legacy 1N957B–1N992B Zener series, engineered for ruggedized voltage regulation in extreme environments including extended temperature ranges and radiation exposure.
FAQ
What is the Zener voltage tolerance of the 1N991B?
The 1N991B has a nominal Zener voltage of 180 V with a ±5% tolerance, as indicated by the "B" suffix per JEDEC standard. This means the actual measured Zener voltage at 0.68 mA test current falls between 171 V and 189 V at 25°C, confirmed in the Electrical Characteristics table on page 2 of the Microsemi datasheet.
Can the 1N991B be used in surface-mount designs?
No-the 1N991B is exclusively packaged in the axial-leaded DO-35 (DO-204AH) glass case and is not a surface-mount device. For SMT equivalents, Microsemi offers the MLL991B in DO-213AA (MELF) package; the 1N991B itself requires through-hole mounting with 3/8" lead length for thermal rating compliance.
What is the maximum steady-state power dissipation for the 1N991B?
The 1N991B is rated for 500 mW steady-state power dissipation at lead temperature (TL) below 50°C with 3/8" (10 mm) lead length from the body. At ambient temperature (TA) < 25°C on FR4 board with specified copper pads, it delivers 480 mW-both values are defined in the Maximum Ratings section of the Microsemi datasheet.
Does the 1N991B require special ESD handling?
No-the 1N991B is nonsensitive to electrostatic discharge per MIL-STD-750 Method 1020, as stated in the Features section. Standard industry ESD precautions are sufficient; no additional shielding or grounding protocols beyond typical handling for discrete semiconductors are required for the 1N991B.
Is the 1N991B RoHS compliant?
The base 1N991B is not RoHS compliant; however, the RoHS-compliant version is designated as 1N991B-e3, achieved by adding the "e3" suffix. This variant uses annealed matte-tin plating instead of tin-lead and meets EU RoHS Directive 2011/65/EU requirements, as documented in the Features and Mechanical Packaging sections.
1N991B 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:
- ±5%
- 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
1N991B FAQ
1.How can I place an order for 1N991B through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N991B 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 1N991B reliable?
The price and inventory of 1N991B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N991B is usually 5 days.
3.What payment methods are accepted for 1N991B?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N991B transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1N991B?
1N991B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N991B 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 1N991B?
For technical support, including 1N991B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N991B requirements.
6.How does Aetrix verify that 1N991B is sourced from the original manufacturer or authorized distributors?
All 1N991B 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 1N991B meets industry standards.
7.What is the process for return or replacement of 1N991B?
All 1N991B units undergo pre-shipment inspection (PSI). If there is an issue with 1N991B, 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 1N991B part is unused and in its original packaging.
Return procedure for 1N991B:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1N991B 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
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