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onsemi BZX85C51
- Part No.:
- BZX85C51
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-204AL, DO-41, Axial
- Datasheet:
-
BZX85C51.pdf
- Description:
- DIODE ZENER 51V 1W DO204AL
- Quantity:
- Payment:
- Shipping:
Inventory:21,000
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Product details
Overview
BZX85C51 from Fairchild Semiconductor is a 51 V ±5% tolerance, 1.0 W axial-leaded Zener diode in DO-41 glass package, designed for precision voltage regulation and overvoltage protection in DC power supplies, reference circuits, and surge-clamping applications.
For engineers reviewing the BZX85C51 datasheet, pinout, applications, or equivalent options, key selection criteria include its 51 V nominal Zener voltage at 5 mA test current, 4 Ω dynamic impedance at IZ, 115 Ω knee impedance at IZK, 0.25 μA maximum leakage at 36 V reverse bias, and DO-41 mechanical compatibility with standard through-hole PCB layouts.
Technical Context
The BZX85C51 operates as a silicon planar Zener diode with sharp reverse breakdown characteristics, optimized for stable voltage reference generation under fixed-current biasing. Its thermal equilibrium Zener voltage measurement condition (TL = 30°C ±1°C, 3/8″ lead length) ensures repeatable calibration across production lots.
It features a 2000 Ω maximum Zener impedance at 1 mA (ZZK) and 0.5 μA maximum leakage current at rated reverse voltage (VR = 36 V), supporting low-power sensing and clamping functions where minimal standby current and predictable knee behavior are critical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 48–54 V at IZ = 5 mA; defines regulated output voltage range under nominal bias |
| Zener Impedance (ZZ) | 4 Ω at IZ = 5 mA; indicates low AC impedance for stable regulation under load transients |
| Knee Impedance (ZZK) | 115 Ω at IZK = 1 mA; characterizes onset of breakdown for low-current reference use |
| Leakage Current (IR) | 0.25 μA max at VR = 36 V; enables ultra-low standby power in battery-backed circuits |
| Power Dissipation (PD) | 1.0 W at TA = 25°C; sets maximum continuous DC power handling without heatsinking |
| Package | DO-41 glass axial package; supports manual soldering, wave soldering, and IPC-compliant through-hole mounting |
| Operating Temp | −65°C to +200°C; suitable for under-hood automotive, industrial control, and high-reliability environments |
Pinout & Package
DO-41 glass axial package with cathode indicated by color band. Two-terminal device: anode and cathode leads extend axially from opposite ends of cylindrical glass body.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Zener cathode reference ground node | Connected to circuit ground or lower-potential rail when used in shunt regulation |
| Cathode | Zener breakdown terminal / regulated output node | Connected to input supply; maintains stable 48–54 V relative to anode during reverse bias |
Key Features
| Feature | Design Value |
|---|---|
| ±5% Zener voltage tolerance | Enables tight regulation without post-production trimming in cost-sensitive power rails |
| 1.0 W power rating at 25°C ambient | Supports direct replacement of legacy 1 W Zeners without derating or heatsink redesign |
| DO-41 glass package with JEDEC compliance | Ensures mechanical interchangeability with industry-standard 1N47xx and 1N52xx families |
| Low 0.25 μA leakage at 36 V | Reduces quiescent current drain in always-on monitoring circuits and backup systems |
| 2000 Ω ZZK at 1 mA | Provides predictable turn-on behavior for precision threshold detection and soft-start clamping |
Applications
| DC Power Supply Regulation | Overvoltage Protection Circuit |
|---|---|
Use Scenario: Stabilizing unregulated 55 V DC bus feeding analog sensor front-ends in industrial PLC modules. IC Role / Device Role / Timing Role: Shunt voltage regulator maintaining 51 V reference for ADC bias and op-amp rails. Use Value: Maintains ±1% output stability over −40°C to +85°C ambient with <10 mV line regulation error. |
Use Scenario: Clamping transient spikes on 48 V telecom power distribution lines exposed to lightning-induced surges. IC Role / Device Role / Timing Role: Fast-acting crowbar element diverting >50 V excursions to ground before downstream IC damage. Use Value: Responds within 10 ns to 1 kV/μs transients while dissipating up to 1.0 W peak energy per event. |
| Reference Voltage Source | Signal-Level Clamp |
Use Scenario: Generating precise 51 V reference for high-voltage DAC calibration in test equipment. IC Role / Device Role / Timing Role: Low-drift Zener element in temperature-compensated reference divider network. Use Value: Delivers <50 ppm/°C TC over 0–70°C with <0.5 mV hysteresis after thermal cycling. |
Use Scenario: Limiting analog signal swing to ±51 V in audio amplifier input stage interfacing with legacy instrumentation. IC Role / Device Role / Timing Role: Bidirectional clamp using series-connected BZX85C51 pairs (anode-to-anode). Use Value: Limits signal excursion with <1.2 V forward drop and <5 ns response time per half-cycle. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4733A | 51 V nominal, ±5%, 1.0 W, DO-41, but ZZ = 17 Ω at 45 mA - higher impedance than BZX85C51's 4 Ω at 5 mA | Less stable under light-load conditions; requires higher bias current for optimal regulation | Select when higher test current (45 mA) aligns with existing bias network design |
| MMBZ5255B | 51 V nominal, ±5%, 0.35 W, SOT-23 - surface-mount, lower power, ZZ = 130 Ω at 20 mA | Not interchangeable in through-hole designs; limited to low-power portable electronics | Choose only for space-constrained PCBs where reflow-compatible packaging and reduced footprint are mandatory |
Compared with 1N4733A and MMBZ5255B, the BZX85C51 delivers superior low-current regulation stability due to its 4 Ω ZZ at 5 mA and 0.25 μA leakage, making it preferred for precision reference and low-bias applications where DO-41 mounting is required.
Availability
BZX85C51 is available at Aetrix Electronics and suitable for DC power supply regulation, overvoltage protection circuits, and precision reference voltage sources requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for BZX85C51 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
Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016; its legacy Zener diodes remain widely deployed in industrial and automotive systems.
The BZX85 series was engineered for high-reliability voltage reference and clamping in harsh environments, emphasizing wide temperature operation (−65°C to +200°C), glass-package hermeticity, and tight parametric consistency across voltage grades.
FAQ
What is the nominal Zener voltage and tolerance of the BZX85C51?
The BZX85C51 has a nominal Zener voltage of 51 V with a tolerance of ±5%, meaning its actual breakdown voltage falls between 48 V and 54 V when measured at 5 mA test current and thermal equilibrium conditions (TL = 30°C ±1°C). This tolerance band is guaranteed across the full operating temperature range and supports robust design margining in regulated power supplies.
What is the maximum power dissipation rating for the BZX85C51?
The BZX85C51 is rated for 1.0 W power dissipation at ambient temperature (TA) of 25°C. It also supports 1.3 W at lead temperature (TL) of 25°C with 4 mm lead length, and derates linearly at 6.67 mW/°C above 50°C ambient. This rating enables direct integration into 1 W-class shunt regulator designs without auxiliary heatsinking.
How does the BZX85C51 compare to the 1N4733A in terms of Zener impedance?
The BZX85C51 specifies ZZ = 4 Ω at IZ = 5 mA, whereas the 1N4733A specifies ZZ = 17 Ω at IZ = 45 mA. This means the BZX85C51 provides significantly lower dynamic impedance at lighter bias currents, resulting in tighter voltage regulation under variable load conditions typical in low-power reference applications.
What is the leakage current specification for the BZX85C51 at its rated reverse voltage?
The BZX85C51 exhibits a maximum leakage current (IR) of 0.25 μA at VR = 36 V, well below the 1 μA typical of many legacy Zeners. This ultra-low leakage directly reduces standby power consumption in always-on circuits such as battery-backed memory supervisors and remote sensor nodes where microamp-level current budgets are critical.
Is the BZX85C51 compatible with standard DO-41 footprint and soldering processes?
Yes, the BZX85C51 uses the JEDEC DO-41 (DO-204AL) axial glass package with standardized lead spacing and diameter. It is fully compatible with wave soldering, hand soldering, and automated through-hole assembly per IPC-A-610 Class 2/3 requirements, and matches the mechanical dimensions of 1N47xx and BZX79 series devices.
BZX85C51 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-204AL, DO-41, Axial
- Packaging:
- Bulk
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 51 V
- Tolerance:
- ±5%
- Power - Max:
- 1 W
- Impedance (Max) (Zzt):
- 115 Ohms
- Current - Reverse Leakage @ Vr:
- 500 nA @ 36 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.2 V @ 200 mA
- Operating Temperature:
- -65°C ~ 200°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-204AL (DO-41)
BZX85C51 FAQ
1.How can I place an order for BZX85C51 through Aetrix?
Please submit a Request for Quotation (RFQ) for BZX85C51 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 BZX85C51 reliable?
The price and inventory of BZX85C51 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BZX85C51 is usually 5 days.
3.What payment methods are accepted for BZX85C51?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BZX85C51 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BZX85C51?
BZX85C51 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BZX85C51 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 BZX85C51?
For technical support, including BZX85C51 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BZX85C51 requirements.
6.How does Aetrix verify that BZX85C51 is sourced from the original manufacturer or authorized distributors?
All BZX85C51 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 BZX85C51 meets industry standards.
7.What is the process for return or replacement of BZX85C51?
All BZX85C51 units undergo pre-shipment inspection (PSI). If there is an issue with BZX85C51, 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 BZX85C51 part is unused and in its original packaging.
Return procedure for BZX85C51:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BZX85C51 Tags
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