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Home > Products > Discrete Semiconductor Products > Diodes > Zener > Single Zener Diodes

onsemi 1N5991B_T50A

Name: 1N5991B_T50A
Brand: onsemi
SKU: 1N5991B_T50A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N5991B_T50A

Manufacturer:: onsemi

Category:: Single Zener Diodes

Package:: DO-204AH, DO-35, Axial

Datasheet:: 1N5991B_T50A.pdf

Description:: DIODE ZENER 4.3V 500MW DO35

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Product details

Overview

1N5991B_T50A from Fairchild Semiconductor is a 4.3 V, ±5% tolerance Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C with 4.0 mW/°C derating, used for precision voltage regulation and reference in low-power analog circuits.

For engineers reviewing the 1N5991B_T50A datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance (±5%), zener impedance (88 Ω @ 5 mA), leakage current (5 mA @ 1 V), maximum zener current (116 mA), and thermal stability across -65°C to +200°C operating range.

Technical Context

The 1N5991B_T50A operates as a two-terminal voltage reference device with sharp reverse-breakdown characteristics defined at IZ = 5 mA. Its zener voltage is specified at thermal equilibrium with 3/8″ lead length and TL = 30°C ± 1°C, ensuring stable regulation under controlled PCB thermal conditions.

Zener impedance is measured at nominal test current (88 Ω @ 5 mA) and knee impedance (2500 Ω @ 250 μA), indicating performance in both normal regulation and low-current biasing. Leakage current is guaranteed ≤5 mA at VR = 1 V, supporting reliable turn-off in series-shunt regulator topologies.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	4.3 V nominal, min 4.085 V / max 4.515 V - defines regulated output voltage under 5 mA test current with ±5% tolerance.
Power Dissipation (P_D)	500 mW @ T_L ≤ 75°C - sets maximum continuous power handling on PCB with 3/8″ lead length.
Zener Impedance (Z_Z)	88 Ω @ I_Z = 5 mA - indicates regulation stiffness; lower value enables tighter voltage control under load variation.
Leakage Current (I_R)	5 mA @ V_R = 1 V - confirms minimal reverse conduction below breakdown, critical for low-quiescent circuits.
Max Zener Current (I_ZM)	116 mA - derived from P_D and V_Z, limits safe DC current for sustained regulation without thermal runaway.
Operating Temp Range	-65°C to +200°C - supports deployment in automotive under-hood, industrial motor controls, and aerospace environments.
Forward Voltage (V_F)	1.2 V max @ I_F = 200 mA - ensures predictable forward conduction if used in dual-direction protection or clamp configurations.

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; two-terminal device requiring no external biasing or control signals.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Reverse-biased input terminal	Connected to lower-potential node in shunt regulator; carries full load current when regulating.
Cathode	Regulated output terminal	Provides stable 4.3 V reference relative to anode; marked by axial color band per JEDEC DO-35 standard.

Key Features

Feature	Design Value
±5% Zener Voltage Tolerance	Enables use in applications requiring tighter regulation than generic 10% zeners, such as sensor biasing and ADC references.
Low Zener Impedance (88 Ω)	Minimizes output voltage shift under varying load currents, improving stability in feedback loops and reference buffers.
High Max Operating Temperature (+200°C)	Supports reliability in high-ambient environments like engine control units and power supply hot zones.
DO-35 Glass Package	Provides hermetic sealing and long-term parameter stability versus plastic-packaged alternatives, critical for mission-critical analog functions.
Controlled Knee Impedance (2500 Ω)	Ensures predictable turn-on behavior near breakdown, enabling accurate low-current biasing in startup or monitoring circuits.

Applications

Power Supply Voltage Reference	Sensor Biasing Circuit
Use Scenario: Provides stable 4.3 V reference for linear regulators or op-amp feedback networks in offline AC/DC adapters. IC Role / Device Role / Timing Role: Shunt voltage reference establishing precise output setpoint independent of input ripple or load transients. Use Value: Maintains ±0.215 V regulation window over temperature and life, reducing need for post-production trimming.	Use Scenario: Biases resistive temperature detectors (RTDs) or bridge sensors in industrial process monitors. IC Role / Device Role / Timing Role: Precision current source via series resistor, delivering fixed excitation current proportional to 4.3 V reference. Use Value: Enables <1% measurement error across -40°C to +125°C ambient due to tight V_Z tolerance and low tempco.
Overvoltage Clamp Protection	Microcontroller Reset Circuit
Use Scenario: Clamps transient spikes on 5 V logic rails during ESD or inductive switching events. IC Role / Device Role / Timing Role: Fast-acting shunt protector diverting excess energy above 4.3 V to ground before IC damage occurs. Use Value: Responds within nanoseconds with <5 mA leakage below clamp threshold, preserving signal integrity in high-speed digital systems.	Use Scenario: Generates clean reset pulse for PIC or ARM microcontrollers during brown-out conditions. IC Role / Device Role / Timing Role: Threshold detector combined with RC timing network to assert reset until V_CC exceeds 4.3 V × (R1+R2)/R2. Use Value: Eliminates external supervisor ICs by leveraging tight V_Z tolerance and repeatable knee behavior for deterministic reset release.

Power Supply Voltage Reference

Sensor Biasing Circuit

Use Scenario: Provides stable 4.3 V reference for linear regulators or op-amp feedback networks in offline AC/DC adapters.

IC Role / Device Role / Timing Role: Shunt voltage reference establishing precise output setpoint independent of input ripple or load transients.

Use Value: Maintains ±0.215 V regulation window over temperature and life, reducing need for post-production trimming.

Use Scenario: Biases resistive temperature detectors (RTDs) or bridge sensors in industrial process monitors.

IC Role / Device Role / Timing Role: Precision current source via series resistor, delivering fixed excitation current proportional to 4.3 V reference.

Use Value: Enables <1% measurement error across -40°C to +125°C ambient due to tight V_Z tolerance and low tempco.

Overvoltage Clamp Protection

Microcontroller Reset Circuit

Use Scenario: Clamps transient spikes on 5 V logic rails during ESD or inductive switching events.

IC Role / Device Role / Timing Role: Fast-acting shunt protector diverting excess energy above 4.3 V to ground before IC damage occurs.

Use Value: Responds within nanoseconds with <5 mA leakage below clamp threshold, preserving signal integrity in high-speed digital systems.

Use Scenario: Generates clean reset pulse for PIC or ARM microcontrollers during brown-out conditions.

IC Role / Device Role / Timing Role: Threshold detector combined with RC timing network to assert reset until V_CC exceeds 4.3 V × (R1+R2)/R2.

Use Value: Eliminates external supervisor ICs by leveraging tight V_Z tolerance and repeatable knee behavior for deterministic reset release.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener diode applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4733A	5.1 V nominal, same DO-35 package, 5% tolerance, but higher Z_Z (17 Ω) and lower I_ZM (69 mA)	Less suitable for 4.3 V reference needs; requires circuit redesign for voltage level shift	Select only if system design targets 5.1 V regulation and can accommodate reduced max current headroom.
BZX55-C4V3	Same 4.3 V rating and 5% tolerance, but DO-35 package with different marking and slightly higher Z_Z (100 Ω @ 5 mA)	Compatible in footprint and function, but may exhibit marginally higher output drift under dynamic load	Valid alternative where second-source qualification is required and 12 Ω Z_Z increase is acceptable.

Compared with 1N5991B_T50A, the 1N4733A shifts regulation to 5.1 V and reduces current capability, while BZX55-C4V3 maintains voltage match but trades 12 Ω higher impedance for broader vendor availability-both require validation against thermal derating and leakage specs in final layout.

Availability

1N5991B_T50A is available at Aetrix Electronics and suitable for power supply voltage reference, sensor biasing, overvoltage clamp protection, and microcontroller reset circuits requiring stable component supply and long-term parametric consistency.

Supply support for 1N5991B_T50A 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 diode portfolio remains widely deployed in industrial and automotive systems.

The 1N59xxB series was designed specifically for general-purpose precision voltage regulation in cost-sensitive, thermally demanding applications where DO-35 reliability and ±5% tolerance deliver optimal balance of accuracy and manufacturability.

FAQ

What is the exact zener voltage range for 1N5991B_T50A at 25°C?

The 1N5991B_T50A has a zener voltage range of 4.085 V (minimum) to 4.515 V (maximum) at 25°C, measured at I_Z = 5 mA with 3/8″ lead length and thermal equilibrium at T_L = 30°C ± 1°C. This ±5% tolerance is guaranteed across the full production lot and forms the basis for its use in precision reference designs.

Does 1N5991B_T50A support operation above 100°C ambient?

Yes, the 1N5991B_T50A is rated for junction and storage temperatures from -65°C to +200°C. At ambient temperatures above 75°C, power dissipation must be derated at 4.0 mW/°C; for example, at 125°C ambient, maximum allowable P_D drops to 300 mW, assuming proper PCB thermal design with 3/8″ leads.

How does the zener impedance of 1N5991B_T50A affect regulation accuracy?

The 1N5991B_T50A exhibits 88 Ω zener impedance at 5 mA test current, meaning a 10 mA change in load current causes approximately 0.88 V shift in output voltage. This value directly impacts regulation tightness in shunt configurations and must be factored into feedback loop stability calculations when used with op-amps or regulators.

Can 1N5991B_T50A be used in place of a 5.1 V zener like 1N4733A?

No-1N5991B_T50A is a 4.3 V device and cannot substitute for 1N4733A (5.1 V) without circuit modification. Voltage mismatch would cause incorrect biasing or regulation failure. If 5.1 V is required, 1N4733A or 1N5993B (4.7 V) are closer alternatives, but each demands verification of Z_Z, I_ZM, and thermal derating in the target application.

What is the forward voltage specification for 1N5991B_T50A?

The 1N5991B_T50A has a maximum forward voltage of 1.2 V at 200 mA forward current. This parameter is relevant when the device is used in bidirectional clamping or reverse-polarity protection schemes, ensuring predictable conduction behavior in forward bias mode alongside its primary zener function.

1N5991B_T50A Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: DO-204AH, DO-35, Axial

Packaging:: Tape & Box (TB)

Product Status:: Obsolete

Voltage - Zener (Nom) (Vz):: 4.3 V

Tolerance:: ±5%

Power - Max:: 500 mW

Impedance (Max) (Zzt):: 88 Ohms

Current - Reverse Leakage @ Vr:: 5 µA @ 1 V

Voltage - Forward (Vf) (Max) @ If:: 1.2 V @ 200 mA

Operating Temperature:: -65°C ~ 200°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-35

1N5991B_T50A FAQ

1.How can I place an order for 1N5991B_T50A through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N5991B_T50A 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 1N5991B_T50A reliable?

The price and inventory of 1N5991B_T50A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N5991B_T50A is usually 5 days.

3.What payment methods are accepted for 1N5991B_T50A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N5991B_T50A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N5991B_T50A?

1N5991B_T50A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N5991B_T50A 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 1N5991B_T50A?

For technical support, including 1N5991B_T50A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N5991B_T50A requirements.

6.How does Aetrix verify that 1N5991B_T50A is sourced from the original manufacturer or authorized distributors?

All 1N5991B_T50A 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 1N5991B_T50A meets industry standards.

7.What is the process for return or replacement of 1N5991B_T50A?

All 1N5991B_T50A units undergo pre-shipment inspection (PSI). If there is an issue with 1N5991B_T50A, 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 1N5991B_T50A part is unused and in its original packaging.

Return procedure for 1N5991B_T50A:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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