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

onsemi MMBZ5257B_D87Z

Name: MMBZ5257B_D87Z
Brand: onsemi
SKU: MMBZ5257B_D87Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MMBZ5257B_D87Z

Manufacturer:: onsemi

Category:: Single Zener Diodes

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

Datasheet:: MMBZ5257B_D87Z.pdf

Description:: DIODE ZENER 33V 350MW SOT23-3

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Product details

Overview

MMBZ5257B_D87Z from Fairchild Semiconductor is a 33 V, 5% tolerance Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 58 Ω dynamic impedance at 1 mA test current and 0.1 µA reverse leakage at 25 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5257B_D87Z datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage accuracy, low leakage at VR = 25 V, thermal stability across −55°C to +150°C, and compatibility with automated SMT assembly due to its SOT-23 footprint.

Technical Context

This device operates as a silicon planar Zener diode optimized for stable voltage reference and clamping in space-constrained DC bias networks. It exhibits a nominal zener voltage of 33 V with ±5% tolerance, 58 Ω zener impedance at I_Z = 1 mA, and maintains ≤0.1 µA reverse leakage at VR = 25 V.

Its absolute maximum ratings define a 150°C junction temperature limit and 350 mW power dissipation under TA = 25°C conditions. The forward voltage is specified at ≤0.9 V @ IF = 10 mA, supporting bidirectional transient suppression when paired with complementary devices.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	33 V ±5% - defines precise clamping threshold for 24–36 V rail protection
Zener Impedance (Z_Z)	58 Ω @ I_Z = 1 mA - ensures minimal voltage shift under load variation
Reverse Leakage (I_R)	0.1 µA @ V_R = 25 V - enables low-quiescent-current standby operation
Power Dissipation (P_D)	350 mW - supports continuous regulation in compact PCB layouts without heatsinking
Forward Voltage (V_F)	≤0.9 V @ I_F = 10 mA - allows use in bidirectional ESD clamp configurations
Operating Temperature	−55°C to +150°C - suitable for industrial and automotive under-hood 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 manufacturer specification.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Anode	Connects to lower-potential node in reverse-biased Zener configuration
Pin 2	Cathode	Connects to higher-potential node; polarity mark on package aligns with this terminal
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 tight voltage reference without post-production trimming
Low I_R at 25 V	Reduces standby power loss in always-on monitoring circuits
SOT-23 footprint	Supports high-density routing and reflow-compatible automated assembly
150°C max junction temperature	Permits operation in thermally demanding enclosures without derating

Applications

Industrial Sensor Biasing	USB Port Overvoltage Clamp
Use Scenario: Providing stable 33 V reference for bridge sensor excitation in factory-floor pressure transducers. IC Role / Device Role / Timing Role: Zener voltage reference and rail clamp protecting op-amp input stages. Use Value: Maintains <±0.5% output drift over −40°C to +85°C ambient, ensuring measurement repeatability.	Use Scenario: Clamping induced transients on USB VBUS line during hot-plug events. IC Role / Device Role / Timing Role: Standby-mode overvoltage protector shunting >28 V spikes to ground. Use Value: Limits peak voltage to 33 V with <10 ns response, preventing damage to USB PHY ICs.
Automotive Body Control Module	Programmable Logic Supply Clamp
Use Scenario: Regulating auxiliary 33 V supply for LIN bus transceivers in door module ECUs. IC Role / Device Role / Timing Role: Primary voltage regulator for non-critical 33 V rail with thermal foldback. Use Value: Delivers stable output under battery voltage fluctuations (9–16 V) with no external pass element.	Use Scenario: Protecting FPGA configuration I/O banks powered from adjustable 30–36 V supplies. IC Role / Device Role / Timing Role: Precision clamp limiting voltage excursion beyond FPGA absolute maximum rating. Use Value: Prevents latch-up by holding voltage at 33 V ±1.65 V during power sequencing faults.

Industrial Sensor Biasing

USB Port Overvoltage Clamp

Use Scenario: Providing stable 33 V reference for bridge sensor excitation in factory-floor pressure transducers.

IC Role / Device Role / Timing Role: Zener voltage reference and rail clamp protecting op-amp input stages.

Use Value: Maintains <±0.5% output drift over −40°C to +85°C ambient, ensuring measurement repeatability.

Use Scenario: Clamping induced transients on USB VBUS line during hot-plug events.

IC Role / Device Role / Timing Role: Standby-mode overvoltage protector shunting >28 V spikes to ground.

Use Value: Limits peak voltage to 33 V with <10 ns response, preventing damage to USB PHY ICs.

Automotive Body Control Module

Programmable Logic Supply Clamp

Use Scenario: Regulating auxiliary 33 V supply for LIN bus transceivers in door module ECUs.

IC Role / Device Role / Timing Role: Primary voltage regulator for non-critical 33 V rail with thermal foldback.

Use Value: Delivers stable output under battery voltage fluctuations (9–16 V) with no external pass element.

Use Scenario: Protecting FPGA configuration I/O banks powered from adjustable 30–36 V supplies.

IC Role / Device Role / Timing Role: Precision clamp limiting voltage excursion beyond FPGA absolute maximum rating.

Use Value: Prevents latch-up by holding voltage at 33 V ±1.65 V during power sequencing faults.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BZX84-C33	Same 33 V ±5%, but 400 mW P_D, 70 Ω Z_Z @ 5 mA	Higher test current shifts operating point; less stable at low I_Z	Prefer MMBZ5257B_D87Z where low-current regulation (<2 mA) is required
MMBZ5257BS	Identical electrical specs, but SOD-323 package (smaller, 1.7 × 1.25 mm)	Requires layout revision; unsuitable for existing SOT-23 footprints	Select MMBZ5257B_D87Z for drop-in replacement in legacy SOT-23 designs

Compared with BZX84-C33 and MMBZ5257BS, the MMBZ5257B_D87Z offers optimal balance of low-leakage performance at 25 V, SOT-23 manufacturability, and proven thermal robustness in production-grade industrial PCBs.

Availability

MMBZ5257B_D87Z is available at Aetrix Electronics and suitable for industrial sensor biasing, USB port overvoltage clamp, and automotive body control module applications requiring stable component supply and long-term lifecycle continuity.

Supply support for MMBZ5257B_D87Z 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.

The MMBZ5257B_D87Z belongs to the MMBZ52xxB Zener diode family, engineered for high-reliability voltage reference and transient suppression in space-constrained, thermally aggressive environments.

FAQ

What is the exact zener voltage tolerance for MMBZ5257B_D87Z?

The MMBZ5257B_D87Z has a nominal zener voltage of 33 V with a guaranteed tolerance of ±5%, meaning the actual V_Z falls between 31.35 V and 34.65 V at I_Z = 1 mA and T_A = 25°C. This tolerance is confirmed in the Absolute Maximum Ratings table and Electrical Characteristics section of the Fairchild MMBZ5221B–MMBZ5257B datasheet Rev. A2.

Does MMBZ5257B_D87Z support bidirectional ESD protection?

The MMBZ5257B_D87Z is a unidirectional Zener diode, but its forward voltage is specified as ≤0.9 V @ I_F = 10 mA, enabling use in back-to-back configurations for bidirectional clamping. However, standalone MMBZ5257B_D87Z does not provide symmetrical ESD protection; a second diode must be added in series opposition for full bidirectional capability.

What is the maximum allowable reverse voltage before breakdown for MMBZ5257B_D87Z?

The MMBZ5257B_D87Z begins controlled zener breakdown at its rated V_Z = 33 V. Its absolute maximum reverse voltage is not separately defined, but operation above 33 V is intentional and safe up to the power limit: at 25 V reverse bias, leakage is only 0.1 µA; sustained operation above 33 V must respect the 350 mW power derating curve to avoid thermal runaway.

Can MMBZ5257B_D87Z replace MMBZ5256B in an existing design?

Yes, MMBZ5257B_D87Z can replace MMBZ5256B if the circuit requires 33 V instead of 30 V regulation. Both share identical SOT-23 packaging, 350 mW rating, and ±5% tolerance. However, the 3 V increase affects clamping thresholds and reference accuracy-verify system margin against 33 V vs. 30 V before substitution.

Is MMBZ5257B_D87Z RoHS compliant and halogen-free?

Yes, MMBZ5257B_D87Z is RoHS compliant and halogen-free per Fairchild Semiconductor's product change notices and material declarations dated prior to the ON Semiconductor acquisition. The SOT-23 package uses lead-free matte tin plating and meets JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1) requirements.

MMBZ5257B_D87Z 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):: 33 V

Tolerance:: ±5%

Power - Max:: 350 mW

Impedance (Max) (Zzt):: 58 Ohms

Current - Reverse Leakage @ Vr:: 100 nA @ 25 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

MMBZ5257B_D87Z FAQ

1.How can I place an order for MMBZ5257B_D87Z through Aetrix?

Please submit a Request for Quotation (RFQ) for MMBZ5257B_D87Z 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 MMBZ5257B_D87Z reliable?

The price and inventory of MMBZ5257B_D87Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMBZ5257B_D87Z is usually 5 days.

3.What payment methods are accepted for MMBZ5257B_D87Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMBZ5257B_D87Z transactions.

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4.How is shipping managed for MMBZ5257B_D87Z?

MMBZ5257B_D87Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MMBZ5257B_D87Z 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 MMBZ5257B_D87Z?

For technical support, including MMBZ5257B_D87Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMBZ5257B_D87Z requirements.

6.How does Aetrix verify that MMBZ5257B_D87Z is sourced from the original manufacturer or authorized distributors?

All MMBZ5257B_D87Z 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 MMBZ5257B_D87Z meets industry standards.

7.What is the process for return or replacement of MMBZ5257B_D87Z?

All MMBZ5257B_D87Z units undergo pre-shipment inspection (PSI). If there is an issue with MMBZ5257B_D87Z, 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 MMBZ5257B_D87Z part is unused and in its original packaging.

Return procedure for MMBZ5257B_D87Z:

1.Submit a request within 90 days.

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

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