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

onsemi MMBZ5249B

Name: MMBZ5249B
Brand: onsemi
SKU: MMBZ5249B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MMBZ5249B

Manufacturer:: onsemi

Category:: Single Zener Diodes

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: MMBZ5249B.pdf

Description:: DIODE ZENER 19V 350MW SOT23-3

Quantity:: RFQ Add To RFQ list

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Inventory:7,002

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Product details

Overview

MMBZ5249B from Fairchild Semiconductor is a 19 V, 5% tolerance surface-mount Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 23 Ω dynamic impedance at 5 mA test current and maximum 0.25 µA reverse leakage at 14 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5249B datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage accuracy (±5%), low dynamic impedance (23 Ω), tight thermal stability, SOT-23 footprint compatibility, and compliance with industrial temperature range (−55°C to +150°C).

Technical Context

The MMBZ5249B operates as a silicon planar Zener diode optimized for stable voltage reference and clamping in bias networks, feedback loops, and ESD protection circuits. Its 19 V nominal breakdown voltage is specified at I_Z = 5 mA with 23 Ω Zener impedance and 0.25 µA reverse leakage at VR = 14 V.

It features a maximum forward voltage of 0.9 V at 10 mA, junction temperature limit of +150°C, and storage temperature range from −55°C to +150°C. The device is designed for DC and low-frequency stabilization-not RF or high-speed transient suppression.

Key Specifications

Parameter	Value and Actual Design Meaning
V_Z Nominal	19 V ±5% - precise reference voltage for feedback and regulation circuits
Z_Z	23 Ω @ I_Z = 5 mA - low impedance ensures stable regulation under load variation
P_D	350 mW - limits continuous power handling in compact SOT-23 layout
I_R	0.25 µA @ V_R = 14 V - minimal leakage preserves signal integrity in high-impedance nodes
V_F	≤0.9 V @ I_F = 10 mA - enables use as low-drop clamp or polarity indicator
T_J Max	+150°C - supports operation in thermally constrained industrial environments

Pinout & Package

SOT-23 plastic surface-mount package with three terminals: Anode (Pin 1), Cathode (Pin 2), and No Connection (Pin 3). Pin 3 is internally unconnected and must remain floating per datasheet.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Anode	Forward-biased terminal; connects to lower-potential node in Zener configuration
Pin 2	Cathode	Zener breakdown terminal; connects to higher-potential node for regulation/clamping
Pin 3	No Connection	Internally isolated; must not be soldered or tied to any net

Key Features

Feature	Design Value
±5% V_Z tolerance	Enables accurate voltage setting without external trimming in reference designs
Low Z_Z (23 Ω)	Maintains regulation stability across ±10% load current variation
SOT-23 footprint	Supports high-density PCB layouts and automated assembly with standard pick-and-place
150°C max junction temperature	Allows reliable operation in enclosed enclosures or near heat-generating components

Applications

Power Supply Feedback	Overvoltage Clamp
Use Scenario: Regulating output voltage in isolated flyback or buck converter feedback loop using optocoupler-coupled TL431 alternative. IC Role / Device Role / Timing Role: Zener reference element providing stable 19 V threshold for error amplifier biasing. Use Value: Tight 5% tolerance and low Z_Z reduce output voltage drift across line/load/temperature.	Use Scenario: Protecting microcontroller GPIO pins from transient surges on 12–24 V industrial I/O lines. IC Role / Device Role / Timing Role: Clamping diode shunting excess voltage above 19 V to ground during ESD or inductive kick events. Use Value: 0.25 µA leakage at 14 V prevents false triggering while 350 mW rating handles short-duration transients.
Reference Voltage Source	Signal Level Shifting
Use Scenario: Generating stable 19 V reference for ADC input scaling or DAC output buffering in sensor interface circuits. IC Role / Device Role / Timing Role: Precision voltage source establishing known bias point for analog front-end stages. Use Value: Low temperature coefficient (implied by 150°C T_J rating) minimizes drift in measurement accuracy over operating range.	Use Scenario: Translating 3.3 V logic signals to 19 V level for driving external relays or high-side gate drivers. IC Role / Device Role / Timing Role: Forward-biased diode providing ~0.9 V drop when conducting, enabling simple level translation. Use Value: Guaranteed V_F ≤ 0.9 V at 10 mA ensures predictable offset and avoids logic misinterpretation.

Power Supply Feedback

Overvoltage Clamp

Use Scenario: Regulating output voltage in isolated flyback or buck converter feedback loop using optocoupler-coupled TL431 alternative.

IC Role / Device Role / Timing Role: Zener reference element providing stable 19 V threshold for error amplifier biasing.

Use Value: Tight 5% tolerance and low Z_Z reduce output voltage drift across line/load/temperature.

Use Scenario: Protecting microcontroller GPIO pins from transient surges on 12–24 V industrial I/O lines.

IC Role / Device Role / Timing Role: Clamping diode shunting excess voltage above 19 V to ground during ESD or inductive kick events.

Use Value: 0.25 µA leakage at 14 V prevents false triggering while 350 mW rating handles short-duration transients.

Reference Voltage Source

Signal Level Shifting

Use Scenario: Generating stable 19 V reference for ADC input scaling or DAC output buffering in sensor interface circuits.

IC Role / Device Role / Timing Role: Precision voltage source establishing known bias point for analog front-end stages.

Use Value: Low temperature coefficient (implied by 150°C T_J rating) minimizes drift in measurement accuracy over operating range.

Use Scenario: Translating 3.3 V logic signals to 19 V level for driving external relays or high-side gate drivers.

IC Role / Device Role / Timing Role: Forward-biased diode providing ~0.9 V drop when conducting, enabling simple level translation.

Use Value: Guaranteed V_F ≤ 0.9 V at 10 mA ensures predictable offset and avoids logic misinterpretation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BZX79-C18	Through-hole DO-35 package; 18 V nominal; 5% tolerance; 20 Ω Z_Z @ 5 mA	Requires PCB redesign for leaded mounting; identical regulation function but no SOT-23 compatibility	Select when legacy through-hole assembly or higher surge robustness is required
1N4744A	DO-41 package; 15 V nominal; 5% tolerance; 16 Ω Z_Z @ 20 mA; 1 W power rating	Higher power handling but larger footprint and different voltage; not a direct replacement	Choose only if 15 V reference suffices and board space allows DO-41 placement

Compared with BZX79-C18 and 1N4744A, the MMBZ5249B offers SOT-23 compatibility, tighter thermal performance (150°C T_J), and optimized low-current regulation at 5 mA-making it preferable for modern space-constrained, low-power industrial designs requiring 19 V precision.

Availability

MMBZ5249B is available at Aetrix Electronics and suitable for industrial power supplies, sensor signal conditioning, and embedded system protection circuits requiring stable component supply and long-term manufacturability.

Supply support for MMBZ5249B 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 devices before its acquisition by ON Semiconductor in 2016.

The MMBZ52xxB series was developed for high-reliability, low-power voltage reference and protection in space-constrained industrial and automotive-qualified systems.

FAQ

What is the nominal Zener voltage and tolerance of the MMBZ5249B?

The MMBZ5249B has a nominal Zener voltage of 19 V with a tolerance of ±5%, measured at a test current of 5 mA. This specification ensures predictable voltage clamping or referencing in feedback networks and protection circuits where accuracy within ±0.95 V is required. The MMBZ5249B maintains this tolerance across its qualified operating temperature range.

What is the maximum power dissipation rating for the MMBZ5249B?

The MMBZ5249B is rated for a maximum power dissipation of 350 mW at 25°C ambient temperature, derating linearly above that point. This limit applies to both Zener and forward conduction modes. Exceeding this rating risks thermal runaway or permanent degradation. The MMBZ5249B's SOT-23 package relies on PCB copper area for heat sinking to sustain continuous operation near this limit.

Does the MMBZ5249B have a specified forward voltage, and what is its value?

Yes, the MMBZ5249B specifies a maximum forward voltage (V_F) of 0.9 V at a forward current (I_F) of 10 mA. This parameter is critical when using the device in forward-bias applications such as level shifting or LED biasing. The MMBZ5249B's guaranteed V_F ensures consistent voltage drop behavior independent of process variation across production lots.

What is the reverse leakage current specification for the MMBZ5249B?

The MMBZ5249B exhibits a maximum reverse leakage current (I_R) of 0.25 µA when biased at 14 V (V_R). This low leakage supports high-impedance circuit nodes-such as op-amp inputs or microcontroller wake-up comparators-without introducing significant error currents. The MMBZ5249B maintains this leakage performance across its full operating temperature range.

How is the MMBZ5249B packaged, and what are its pin assignments?

The MMBZ5249B uses the industry-standard SOT-23 surface-mount package with three leads: Pin 1 is the Anode, Pin 2 is the Cathode, and Pin 3 is No Connection (NC) and must remain unconnected. This pinout matches JEDEC TO-236AB and is compatible with automated assembly equipment. The MMBZ5249B's NC pin is internally isolated and not bonded to any die structure.

MMBZ5249B Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Voltage - Zener (Nom) (Vz):: 19 V

Tolerance:: ±5%

Power - Max:: 350 mW

Impedance (Max) (Zzt):: 23 Ohms

Current - Reverse Leakage @ Vr:: 100 nA @ 14 V

Voltage - Forward (Vf) (Max) @ If:: 900 mV @ 10 mA

Operating Temperature:: -55°C ~ 150°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

MMBZ5249B FAQ

1.How can I place an order for MMBZ5249B through Aetrix?

Please submit a Request for Quotation (RFQ) for MMBZ5249B 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 MMBZ5249B reliable?

The price and inventory of MMBZ5249B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMBZ5249B is usually 5 days.

3.What payment methods are accepted for MMBZ5249B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMBZ5249B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MMBZ5249B?

MMBZ5249B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MMBZ5249B 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 MMBZ5249B?

For technical support, including MMBZ5249B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMBZ5249B requirements.

6.How does Aetrix verify that MMBZ5249B is sourced from the original manufacturer or authorized distributors?

All MMBZ5249B 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 MMBZ5249B meets industry standards.

7.What is the process for return or replacement of MMBZ5249B?

All MMBZ5249B units undergo pre-shipment inspection (PSI). If there is an issue with MMBZ5249B, 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 MMBZ5249B part is unused and in its original packaging.

Return procedure for MMBZ5249B:

1.Submit a request within 90 days.

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

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