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onsemi BZX79C18_T50R
- Part No.:
- BZX79C18_T50R
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-204AH, DO-35, Axial
- Datasheet:
-
BZX79C18_T50R.pdf
- Description:
- DIODE ZENER 18V 500MW DO35
- Quantity:
- Payment:
- Shipping:
Inventory:4,685
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Product details
Overview
BZX79C18_T50R from ON Semiconductor is a 18 V, 5% tolerance, 500 mW DO-35 glass-encapsulated Zener diode optimized for voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and precision biasing networks.
For engineers reviewing the BZX79C18_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage (18 V ±5%), dynamic impedance (45 Ω @ 5 mA), leakage current (0.05 μA @ 14.4 V), temperature coefficient (+12.6 mV/°C), and DO-35 package compatibility with through-hole PCB assembly.
Technical Context
This device operates as a reverse-biased silicon junction diode with controlled avalanche breakdown at precisely defined voltage. It maintains stable regulation across 1 mA to 20 mA operating current, with thermal derating of 4.0 mW/°C above 75°C lead temperature.
The BZX79C18_T50R exhibits a positive temperature coefficient (+12.6 mV/°C) - critical for compensating drift in temperature-sensitive analog references - and features low capacitance (34 pF @ 0 V, 1 MHz) suitable for moderate-frequency noise filtering and transient suppression.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 18 V ±5% (17.1–19.1 V range ensures reliable clamping in 18 V nominal systems) |
| Test Current (IZ) | 5 mA (standard bias point for spec validation and design consistency) |
| Dynamic Impedance (ZZ) | 45 Ω @ 5 mA (low impedance enables tight regulation under load variation) |
| Maximum Leakage (IR) | 0.05 μA @ 14.4 V (minimal standby current preserves battery life in low-power circuits) |
| Power Dissipation (PD) | 500 mW @ TL ≤ 75°C (supports continuous operation in compact linear regulators) |
| Temperature Coefficient (TC) | +12.6 mV/°C (positive TC allows compensation pairing with negative-TC components) |
| Junction Temp Range | −65°C to +200°C (enables deployment in automotive under-hood and industrial environments) |
Pinout & Package
DO-35 glass axial package with cathode indicated by color band; two-terminal device requiring no orientation-specific PCB footprint beyond standard 0.4 mm wire diameter lead spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Reference ground node | Connected to circuit common when used in shunt regulation; defines reference potential |
| Cathode | Zener breakdown terminal / Regulated output node | Connected to input rail; clamps voltage to VZ when reverse biased above breakdown threshold |
Key Features
| Feature | Design Value |
|---|---|
| Stable 18 V reference | Guaranteed 17.1–19.1 V range at 5 mA supports ±5% system tolerance budgets |
| Low dynamic impedance | 45 Ω enables <1% output deviation across 1–20 mA load current swing |
| Controlled temperature coefficient | +12.6 mV/°C allows predictable drift modeling and thermal compensation design |
| High-reliability glass package | DO-35 construction provides hermetic sealing and long-term stability in humid environments |
| Low leakage current | 0.05 μA at 14.4 V minimizes error in high-impedance reference divider networks |
Applications
| Switch-Mode Power Supply Feedback | Industrial Sensor Biasing |
|---|---|
Use Scenario: Provides precise 18 V reference for optocoupler-based feedback in isolated DC-DC converters. IC Role / Device Role / Timing Role: Shunt voltage reference defining secondary-side regulation setpoint. Use Value: Tight 5% VZ tolerance and low ZZ ensure ±2% output voltage accuracy across line/load/temperature. | Use Scenario: Supplies stable bias voltage to bridge-based pressure transducers in factory automation nodes. IC Role / Device Role / Timing Role: Precision analog reference source for ratiometric sensor excitation. Use Value: Low leakage (0.05 μA) prevents loading errors in MΩ-range Wheatstone bridge arms. |
| Overvoltage Protection Clamp | Microcontroller I/O Protection |
Use Scenario: Clamps 24 V industrial bus transients to safe levels before entering downstream logic. IC Role / Device Role / Timing Role: Passive crowbar element limiting rail voltage during surge events. Use Value: 500 mW rating sustains 100 ms surges up to 22 V without degradation; DO-35 allows easy placement near connectors. | Use Scenario: Protects 3.3 V MCU GPIO pins from accidental 18 V miswiring in field-serviceable equipment. IC Role / Device Role / Timing Role: Reverse-biased clamp diverting fault current away from ESD structures. Use Value: 18 V breakdown cleanly intercepts overvoltage before damaging 5 V-tolerant I/O cells. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4746A | Same 18 V rating, 1 W power, DO-41 package (larger footprint, higher PD) | Suitable for higher-power regulation where thermal margin is critical | Select when >500 mW dissipation is required; requires PCB layout change |
| MMSZ4702T1G | 18 V SOD-123 surface-mount package, 500 mW, 30 Ω ZZ, 0.1 μA IR | Designed for automated pick-and-place and space-constrained PCBs | Choose for modern high-density designs; not drop-in compatible with DO-35 |
Compared with BZX79C18_T50R, the 1N4746A offers higher power handling but requires larger board area, while the MMSZ4702T1G delivers identical electrical performance in a compact SMT form - both serve distinct mechanical and thermal design priorities rather than direct replacement roles.
Availability
BZX79C18_T50R is available at Aetrix Electronics and suitable for industrial power supplies, sensor interface modules, and embedded overvoltage protection circuits requiring stable component supply and long-lifecycle support.
Supply support for BZX79C18_T50R 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
ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
The BZX79C series was designed specifically for general-purpose voltage regulation and reference applications where cost-effective, through-hole Zener performance and long-term reliability are essential.
FAQ
What is the exact zener voltage tolerance for BZX79C18_T50R?
The BZX79C18_T50R has a nominal zener voltage of 18 V with a guaranteed tolerance of ±5%, meaning its actual breakdown voltage falls between 17.1 V and 19.1 V when measured at 5 mA test current and 25°C ambient. This tolerance is specified per the ON Semiconductor BZX79C2V4–BZX79C56 datasheet Rev. 3, and applies directly to the BZX79C18_T50R variant.
Does BZX79C18_T50R have a positive or negative temperature coefficient?
The BZX79C18_T50R exhibits a positive temperature coefficient of +12.6 mV/°C, meaning its zener voltage increases predictably with rising junction temperature. This behavior is confirmed in the Electrical Characteristics table for the BZX79C18 entry and is typical for Zener diodes rated above ~6 V, enabling thermal drift compensation in precision analog designs using the BZX79C18_T50R.
What is the maximum power dissipation for BZX79C18_T50R and how does it derate with temperature?
The BZX79C18_T50R has a maximum power dissipation of 500 mW at lead temperature (TL) ≤ 75°C with 3/8″ lead length. Above 75°C, it derates linearly at 4.0 mW/°C - for example, at TL = 100°C, allowable power drops to 400 mW. This derating curve is defined in the Absolute Maximum Ratings section of the official ON Semiconductor datasheet for BZX79C18_T50R.
What package type does BZX79C18_T50R use and how is polarity marked?
The BZX79C18_T50R uses the DO-35 glass axial package with cathode identified by a single color band on the body. The anode and cathode leads are unmarked otherwise, and the device must be oriented with the banded end connected to the higher-potential node in reverse-bias applications. This marking convention and package geometry are standardized across the full BZX79C series, including BZX79C18_T50R.
What is the dynamic impedance of BZX79C18_T50R and why does it matter?
The dynamic impedance (ZZ) of BZX79C18_T50R is 45 Ω at 5 mA test current, representing its small-signal AC resistance near the breakdown knee. This value directly impacts regulation accuracy: lower ZZ means smaller output voltage variation under changing load current. For BZX79C18_T50R, 45 Ω enables sub-1% voltage deviation across typical operating ranges, making it suitable for stable reference and clamping functions.
BZX79C18_T50R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-204AH, DO-35, Axial
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Voltage - Zener (Nom) (Vz):
- 18 V
- Tolerance:
- ±5%
- Power - Max:
- 500 mW
- Impedance (Max) (Zzt):
- 45 Ohms
- Current - Reverse Leakage @ Vr:
- 50 nA @ 12.6 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.5 V @ 100 mA
- Operating Temperature:
- -65°C ~ 200°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-35
BZX79C18_T50R FAQ
1.How can I place an order for BZX79C18_T50R through Aetrix?
Please submit a Request for Quotation (RFQ) for BZX79C18_T50R 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 BZX79C18_T50R reliable?
The price and inventory of BZX79C18_T50R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BZX79C18_T50R is usually 5 days.
3.What payment methods are accepted for BZX79C18_T50R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BZX79C18_T50R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BZX79C18_T50R?
BZX79C18_T50R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BZX79C18_T50R 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 BZX79C18_T50R?
For technical support, including BZX79C18_T50R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BZX79C18_T50R requirements.
6.How does Aetrix verify that BZX79C18_T50R is sourced from the original manufacturer or authorized distributors?
All BZX79C18_T50R 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 BZX79C18_T50R meets industry standards.
7.What is the process for return or replacement of BZX79C18_T50R?
All BZX79C18_T50R units undergo pre-shipment inspection (PSI). If there is an issue with BZX79C18_T50R, 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 BZX79C18_T50R part is unused and in its original packaging.
Return procedure for BZX79C18_T50R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BZX79C18_T50R Tags
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