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onsemi BZX79C51
- Part No.:
- BZX79C51
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-204AH, DO-35, Axial
- Datasheet:
-
BZX79C51.pdf
- Description:
- DIODE ZENER 51V 500MW DO35
- Quantity:
- Payment:
- Shipping:
Inventory:4,367
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Product details
Overview
BZX79C51 from ON Semiconductor is a 51 V ±5% tolerance Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C, with 180 Ω dynamic impedance at 2 mA test current and 0.5 μA maximum leakage current at 39.2 V reverse voltage. It provides precise voltage regulation in low-power reference and protection circuits.
For engineers reviewing the BZX79C51 datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage accuracy (±5%), thermal coefficient (+1.2 mV/°C), junction capacitance (19 pF at 0 V), maximum power rating (500 mW), and DO-35 mechanical compatibility for through-hole PCB layouts.
Technical Context
The BZX79C51 operates as a silicon planar Zener diode optimized for stable voltage reference and overvoltage clamping in DC bias networks. Its 51 V nominal breakdown voltage is specified at 2 mA test current, with 180 Ω dynamic impedance ensuring predictable regulation under small-signal load variations.
It features a positive temperature coefficient of +1.2 mV/°C above 4.7 V, enabling predictable drift compensation in temperature-sensitive references. The device is rated for operation from –65 °C to +200 °C and exhibits 19 pF junction capacitance at 0 V, limiting high-frequency noise coupling in precision analog paths.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 48 V min / 54 V max at IZ = 2 mA - defines usable regulation window for 51 V nominal reference |
| Power Dissipation (PD) | 500 mW @ TL ≤ 75°C - sets maximum continuous DC power handling before thermal derating |
| Dynamic Impedance (ZZ) | 180 Ω max @ IZ = 2 mA - determines output voltage variation under load current changes |
| Leakage Current (IR) | 0.5 μA max @ VR = 39.2 V - ensures minimal error current in high-impedance bias networks |
| Junction Capacitance (CJ) | 19 pF @ VR = 0 V, f = 1 MHz - impacts high-frequency filtering and noise rejection capability |
| Temperature Coefficient (TC) | +1.2 mV/°C - quantifies voltage drift per degree Celsius above 4.7 V threshold |
| Tolerance | ±5% - specifies allowable deviation from nominal 51 V rating at 25°C |
Pinout & Package
DO-35 glass axial package with cathode indicated by color band; two-terminal device requiring no orientation-specific PCB footprint beyond standard axial lead spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Zener cathode reference node | Connected to lower-potential side in reverse-bias regulation configuration |
| Cathode | Zener breakdown terminal / voltage reference output | Marked with color band; connected to higher-potential side to enable controlled avalanche conduction |
Key Features
| Feature | Design Value |
|---|---|
| Stable Zener voltage reference | 51 V ±5% with +1.2 mV/°C TC enables predictable mid-range voltage referencing |
| Low leakage current | ≤0.5 μA at 39.2 V supports high-impedance biasing without loading error |
| Controlled dynamic impedance | 180 Ω max at 2 mA ensures <100 mV output shift for ±1 mA load variation |
| High-temperature operation | –65 °C to +200 °C range allows use in automotive engine bay or industrial control enclosures |
| DO-35 mechanical standardization | Industry-standard axial glass package simplifies hand-soldering and automated insertion |
Applications
| Industrial Power Supply Monitoring | Automotive ECU Reference Voltage |
|---|---|
Use Scenario: Monitoring 48 V battery rail in telecom power systems to trigger undervoltage lockout. IC Role / Device Role / Timing Role: Zener diode providing stable 51 V threshold for comparator input. Use Value: ±5% tolerance and +1.2 mV/°C TC ensure reliable trip point across –40 °C to +105 °C operating range. | Use Scenario: Generating precision bias voltage for sensor signal conditioning in engine control units. IC Role / Device Role / Timing Role: Voltage reference source for ADC reference divider network. Use Value: 0.5 μA leakage prevents loading error in high-resistance divider chains feeding 12-bit ADCs. |
| LED Driver Overvoltage Clamp | Programmable Logic Controller Input Protection |
Use Scenario: Clamping transient spikes on constant-current LED string drivers in streetlight fixtures. IC Role / Device Role / Timing Role: Shunt protection device absorbing surge energy above 51 V. Use Value: 500 mW power rating sustains short-duration transients without thermal runaway. | Use Scenario: Protecting 24 V digital input channels in PLC modules against field-wiring faults. IC Role / Device Role / Timing Role: Reverse-biased clamp limiting input voltage to safe logic levels. Use Value: 19 pF junction capacitance avoids signal integrity degradation on 10 kHz–1 MHz input signals. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N5257B | Same 51 V nominal, ±5% tolerance, but 175 Ω ZZ @ 20 mA (vs. 180 Ω @ 2 mA); DO-35 package | Higher test current shifts regulation point - less suitable for micro-power bias networks | Select BZX79C51 when low-test-current operation (<5 mA) or tighter low-current ZZ spec is required |
| MMSZ5257B | SOD-123 surface-mount package; identical 51 V/±5% rating but 150 Ω ZZ @ 20 mA and 100 mW PD | Not interchangeable due to 80% lower power rating and different footprint - requires PCB redesign | Choose MMSZ5257B only for space-constrained designs where 100 mW suffices and reflow assembly is available |
Compared with 1N5257B and MMSZ5257B, the BZX79C51 offers superior low-current regulation stability (tested at 2 mA vs. 20 mA), higher power headroom (500 mW vs. 500 mW and 100 mW), and proven thermal robustness up to +200 °C - making it preferred for industrial and automotive analog reference designs.
Availability
BZX79C51 is available at Aetrix Electronics and suitable for industrial power supply monitoring, automotive ECU reference voltage generation, and LED driver overvoltage clamping requiring stable component supply and long-term obsolescence management.
Supply support for BZX79C51 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 power management, analog, sensors, and discrete devices for automotive, industrial, and cloud power applications.
The BZX79C series was designed as a general-purpose, cost-optimized Zener diode family for voltage regulation and protection in DC power rails, offering tight tolerance and consistent thermal behavior across 2.4 V to 56 V ratings.
FAQ
What is the Zener voltage tolerance for BZX79C51?
The BZX79C51 has a guaranteed Zener voltage tolerance of ±5% at 25°C, meaning its breakdown voltage falls between 48.0 V and 54.0 V when tested at 2 mA. This tolerance remains valid across the full operating temperature range of –65 °C to +200 °C, though actual voltage drift follows the +1.2 mV/°C temperature coefficient above 4.7 V. The BZX79C51 datasheet confirms this specification under Electrical Characteristics at TA = 25°C.
What is the maximum power dissipation of BZX79C51 and how does it change with temperature?
The BZX79C51 is rated for 500 mW power dissipation 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 100°C lead temperature, maximum allowable power drops to 400 mW. This derating ensures junction temperature stays within safe limits. The BZX79C51 absolute maximum ratings table explicitly defines this behavior.
What is the dynamic impedance of BZX79C51 and why does it matter?
The BZX79C51 has a maximum dynamic impedance (ZZ) of 180 Ω measured at IZ = 2 mA. This value quantifies how much the Zener voltage changes in response to small variations in current - a lower ZZ means better regulation stability. For instance, a ±1 mA current swing causes ≤180 mV output variation. The BZX79C51's ZZ is specified in the Electrical Characteristics table and directly impacts reference accuracy in precision analog circuits.
Does BZX79C51 have a specified leakage current, and at what voltage is it measured?
Yes, the BZX79C51 has a maximum leakage current (IR) of 0.5 μA, measured at a reverse voltage (VR) of 39.2 V - which is approximately 77% of its nominal 51 V Zener voltage. This low leakage ensures minimal error current in high-impedance bias networks, such as those used in sensor front-ends or comparator reference dividers. The value is confirmed in the Electrical Characteristics table under "Leakage Current".
What package type is used for BZX79C51 and how is polarity marked?
The BZX79C51 uses the DO-35 glass axial package, with cathode polarity indicated by a distinct color band near one lead end. This marking aligns with industry-standard diode identification and ensures correct orientation during manual or automated placement. The DO-35 outline and cathode band requirement are documented in the "Top Mark Information" section of the BZX79C2V4–BZX79C56 datasheet.
BZX79C51 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-204AH, DO-35, Axial
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Voltage - Zener (Nom) (Vz):
- 51 V
- Tolerance:
- ±5%
- Power - Max:
- 500 mW
- Impedance (Max) (Zzt):
- 180 Ohms
- Current - Reverse Leakage @ Vr:
- 500 nA @ 35.7 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
BZX79C51 FAQ
1.How can I place an order for BZX79C51 through Aetrix?
Please submit a Request for Quotation (RFQ) for BZX79C51 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 BZX79C51 reliable?
The price and inventory of BZX79C51 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BZX79C51 is usually 5 days.
3.What payment methods are accepted for BZX79C51?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BZX79C51 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BZX79C51?
BZX79C51 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BZX79C51 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 BZX79C51?
For technical support, including BZX79C51 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BZX79C51 requirements.
6.How does Aetrix verify that BZX79C51 is sourced from the original manufacturer or authorized distributors?
All BZX79C51 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 BZX79C51 meets industry standards.
7.What is the process for return or replacement of BZX79C51?
All BZX79C51 units undergo pre-shipment inspection (PSI). If there is an issue with BZX79C51, 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 BZX79C51 part is unused and in its original packaging.
Return procedure for BZX79C51:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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