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Microchip Technology 1N973B
- Part No.:
- 1N973B
- Manufacturer:
- Microchip Technology
- Category:
- Single Zener Diodes
- Package:
- DO-204AA, DO-7, Axial
- Datasheet:
-
1N973B.pdf
- Description:
- DIODE ZENER 33V 500MW DO7
- Quantity:
- Payment:
- Shipping:
Inventory:7,777
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Product details
Overview
1N973B from Microsemi is a silicon 500 mW axial-lead Zener diode with nominal Zener voltage 33 V, ±5% tolerance (B suffix), 3.8 mA Zener test current, 58 Ω dynamic impedance at IZT, and +0.092 %/°C temperature coefficient. It regulates voltage in low-power reference and protection circuits across industrial and aerospace systems operating from –65°C to +175°C.
For engineers reviewing the 1N973B datasheet, 1N973B pinout, 1N973B application, or 1N973B equivalent, key selection criteria include its DO-35 glass package, cathode-band polarity marking, 400 mW maximum DC Zener current rating at 75°C lead temperature, and compatibility with manual or wave-soldering processes per MIL-STD-750.
Technical Context
The 1N973B operates as a reverse-biased voltage reference device with sharp breakdown knee verified by dual-point Zener impedance measurement per MicroNote 202. Its regulation stability relies on metallurgical bond integrity (optional –1 suffix) and hermetic glass sealing, enabling operation up to 175°C junction temperature.
Thermal resistance is 250 °C/W junction-to-lead at 3/8″ lead length, and 310 °C/W junction-to-ambient on FR4 with defined copper pad geometry. Forward voltage is ≤1.1 V at 200 mA, confirming standard silicon P-N junction behavior distinct from Schottky or avalanche structures.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal Zener Voltage | 33 V - stable regulation point under 3.8 mA test current, ±5% tolerance ensures predictable clamping in feedback loops |
| Zener Test Current (IZT) | 3.8 mA - minimum current required to achieve rated VZ; used for calibration and impedance measurement |
| Zener Impedance (ZZT) | 58 Ω at IZT - defines voltage deviation under load transients; lower than 1N972B (49 Ω) but higher than 1N974B (70 Ω) |
| Max DC Zener Current (IZM) | 11 mA - derived for 400 mW dissipation at 75°C lead temp; sets upper limit for continuous regulation current |
| Temp Coefficient (αVZ) | +0.092 %/°C - positive drift rate; enables predictable compensation in temperature-stable references above 20 V |
| Reverse Leakage (IR) | 5 μA at 25 V - confirms low off-state power loss in high-impedance bias networks |
| Package | DO-35 (DO-204AH) - glass axial-leaded case with cathode band; supports through-hole mounting and manual soldering |
Pinout & Package
DO-35 (DO-204AH) glass axial-leaded package with hermetically sealed body, tin-lead or RoHS-compliant matte-tin plating, and cathode indicated by a single dark band. Polarity must be observed: banded end is cathode and must be held positive relative to anode during Zener operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Zener cathode reference node | Connected to circuit ground or lower potential; forms reference return path in shunt regulator topologies |
| Cathode | Zener regulation terminal / voltage clamp input | Banded end; connected to unregulated supply rail; maintains 33 V drop when reverse-biased above breakdown threshold |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC-registered 1N973B series | Industry-standard part numbering and electrical definition ensuring cross-manufacturer interchangeability in legacy designs |
| ±5% Zener voltage tolerance (B suffix) | Enables cost-effective voltage referencing where tight regulation is not required, e.g., overvoltage detection thresholds |
| –65°C to +175°C operating range | Validated for extended-temperature applications including downhole tools, avionics, and engine control modules |
| Nonsensitive to ESD per MIL-STD-750 Method 1020 | Eliminates need for external ESD protection in handling and assembly, reducing BOM count in ruggedized systems |
| Hermetic glass DO-35 construction | Provides long-term reliability in humid or corrosive environments without conformal coating or encapsulation |
Applications
| Industrial Power Supply Monitoring | Aerospace Voltage Reference |
|---|---|
Use Scenario: Monitoring +48 V telecom rectifier output for overvoltage shutdown. IC Role / Device Role / Timing Role: Shunt regulator providing precise 33 V reference to comparator input. Use Value: 58 Ω ZZT ensures <100 mV deviation under 1 mA load shift, meeting ITU-T L.120 fault-detection timing margins. |
Use Scenario: Biasing analog sensor signal conditioning in satellite payload telemetry. IC Role / Device Role / Timing Role: Stable 33 V reference for ADC reference buffer in radiation-hardened subsystems. Use Value: +0.092 %/°C tempco and –65°C to +175°C rating enable <±1.5% reference drift across orbital thermal cycles. |
| Automotive Engine Control Unit | Test & Measurement Equipment |
Use Scenario: Clamping 12 V battery line against load dump spikes in ECU power rail. IC Role / Device Role / Timing Role: Transient voltage suppressor in parallel with microcontroller VDD. Use Value: 11 mA IZM and 400 mW power rating sustain 100 ms surges without degradation per ISO 7637-2 Pulse 5a. |
Use Scenario: Calibrating bench multimeter internal reference divider network. IC Role / Device Role / Timing Role: Precision Zener element in 33 V calibration standard module. Use Value: JEDEC registration and ±5% tolerance allow traceable comparison against NIST-traceable standards without recalibration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4747A (ON Semiconductor) | 33 V, ±5%, 1 W rating, DO-41 package, 100 Ω ZZT at 37 mA | Higher power and impedance; requires larger PCB footprint and different thermal layout | Select when >500 mW surge capability or higher IZM (>37 mA) is required; not drop-in due to DO-41 vs. DO-35 mechanical mismatch |
| BZX55C33 (Vishay) | 33 V, ±5%, 500 mW, DO-35 package, 80 Ω ZZT at 5 mA | Higher dynamic impedance and 5 mA IZT; less stable regulation at low currents | Acceptable for non-critical biasing where 3.8 mA IZT compliance is not mandatory; same DO-35 footprint enables direct replacement if thermal derating is verified |
Compared with 1N973B, 1N4747A offers higher surge robustness but demands PCB redesign, while BZX55C33 matches the DO-35 form factor but exhibits 38% higher ZZT, impacting regulation accuracy in low-current precision references.
Availability
1N973B is available at Aetrix Electronics and suitable for industrial power supply monitoring, aerospace voltage reference, automotive engine control unit, and test & measurement equipment requiring stable component supply across extended temperature ranges and long lifecycle programs.
Supply support for 1N973B 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, radiation-hardened, and high-temperature analog and discrete components for defense, aerospace, and industrial markets.
The 1N973B belongs to Microsemi's legacy 1N957B–1N992B DO-35 Zener series designed for mission-critical voltage regulation where hermetic sealing, wide temperature operation, and JEDEC standardization are essential.
FAQ
What is the Zener voltage tolerance for 1N973B?
The 1N973B has a nominal Zener voltage of 33 V with a ±5% tolerance, indicated by the "B" suffix per JEDEC standard. This means the actual measured VZ at 3.8 mA falls between 31.35 V and 34.65 V at 25°C. The tolerance remains valid across the full –65°C to +175°C operating range, though voltage drift follows the +0.092 %/°C coefficient.
Can 1N973B be used in surface-mount designs?
No, the 1N973B is exclusively offered in the axial-leaded DO-35 (DO-204AH) glass package and is not a surface-mount device. For SMT equivalents, Microsemi offers the MLL973B in DO-213AA (MELF) package; however, 1N973B itself requires through-hole mounting and wave or hand soldering per MIL-STD-750 Method 2026.
What is the maximum steady-state power dissipation for 1N973B?
The 1N973B is rated for 500 mW steady-state power at lead temperature <50°C (3/8″ from body), but its usable DC Zener current is limited to 11 mA (IZM) to maintain 400 mW dissipation at 75°C lead temperature. Derating begins linearly above 50°C per Figure 1 in the datasheet, reaching zero power at 175°C ambient.
How is polarity marked on the 1N973B package?
The 1N973B uses a single dark band on the glass body to indicate the cathode terminal. During Zener operation, the banded end must be held positive relative to the unmarked (anode) end. This polarity is critical-reverse connection results in forward conduction (~1.1 V drop) rather than 33 V regulation.
Is 1N973B compliant with RoHS requirements?
Yes, the RoHS-compliant version of 1N973B is designated as 1N973Be3, where the "e3" suffix indicates annealed matte-tin plating and full compliance with EU Directive 2011/65/EU. Standard 1N973B uses Sn/Pb plating; both variants share identical electrical specifications and DO-35 mechanical dimensions.
1N973B Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- DO-204AA, DO-7, Axial
- Packaging:
- Bulk
- Product Status:
- Discontinued at Digi-Key
- Voltage - Zener (Nom) (Vz):
- 33 V
- Tolerance:
- ±5%
- Power - Max:
- 500 mW
- Impedance (Max) (Zzt):
- 58 Ohms
- Current - Reverse Leakage @ Vr:
- 5 µA @ 25.1 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
1N973B FAQ
1.How can I place an order for 1N973B through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N973B 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 1N973B reliable?
The price and inventory of 1N973B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N973B is usually 5 days.
3.What payment methods are accepted for 1N973B?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N973B transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1N973B?
1N973B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N973B 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 1N973B?
For technical support, including 1N973B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N973B requirements.
6.How does Aetrix verify that 1N973B is sourced from the original manufacturer or authorized distributors?
All 1N973B 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 1N973B meets industry standards.
7.What is the process for return or replacement of 1N973B?
All 1N973B units undergo pre-shipment inspection (PSI). If there is an issue with 1N973B, 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 1N973B part is unused and in its original packaging.
Return procedure for 1N973B:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1N973B 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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