onsemi MMBZ5238B_D87Z

Overview

MMBZ5238B_D87Z from Fairchild Semiconductor is a 5% tolerance, 8.7 V Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 8 Ω dynamic impedance at 20 mA test current and 3.0 µA reverse leakage at 6.5 V, used for voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5238B_D87Z datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage tolerance, dynamic impedance at specified test current, reverse leakage at rated VR, thermal derating behavior, and SOT-23 footprint compatibility with board-level ESD and transient suppression requirements.

Technical Context

The MMBZ5238B_D87Z 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 8.7 V ±5% at I_Z = 20 mA, with dynamic impedance (Z_Z) of 8 Ω and knee impedance (Z_ZK) of 20 Ω at I_ZK = 0.25 mA.

Its absolute maximum ratings define a 150 °C junction temperature limit and -55 to +150 °C storage range, with forward voltage capped at 0.9 V at 10 mA. Reverse leakage remains ≤3.0 µA at 6.5 V, supporting low-quiescent-current designs.

Key Specifications

Pinout & Package

SOT-23 surface-mount plastic package with gull-wing leads; standardized 3-pin outline where Pin 1 is anode, Pin 2 is cathode, and Pin 3 is NC (no connection) per Fairchild's connection diagram.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBZ5238B_D87Z, BZX84-C8V2 trades tighter package compatibility for reduced regulation precision at higher currents, while MMBZ5237B offers identical impedance and thermal behavior at a lower voltage - both require explicit validation of clamping headroom and leakage impact in the target bias network.

Availability

MMBZ5238B_D87Z is available at Aetrix Electronics and suitable for industrial sensor biasing, microcontroller I/O protection, and low-power voltage reference applications requiring stable component supply and long-term obsolescence management.

Supply support for MMBZ5238B_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 designer of high-performance analog and discrete semiconductors, acquired by ON Semiconductor in 2016; known for rugged, industry-standard Zener and switching diodes.

The MMBZ52xxB series was engineered for general-purpose voltage regulation and transient suppression in cost-sensitive, space-constrained consumer and industrial electronics - emphasizing consistent Zener characteristics and SOT-23 manufacturability.

FAQ

What is the Zener voltage tolerance for MMBZ5238B_D87Z?

The MMBZ5238B_D87Z has a Zener voltage tolerance of ±5% at 20 mA test current, resulting in a guaranteed V_Z range of 8.27 V to 9.14 V. This tolerance is measured under standard conditions (T_A = 25 °C) and applies to all units shipped as MMBZ5238B_D87Z. The 5% spec ensures predictable clamping behavior across production batches without requiring unit-level trimming.

Does MMBZ5238B_D87Z support bidirectional transient suppression?

Yes, MMBZ5238B_D87Z supports bidirectional transient suppression: its forward voltage is ≤0.9 V at 10 mA, and its reverse Zener voltage is 8.7 V ±5%. When placed across a signal line with appropriate series current limiting, it conducts in forward bias for negative transients and reverse bias for positive transients - making MMBZ5238B_D87Z suitable for I/O rail protection in mixed-signal systems.

What is the maximum power dissipation of MMBZ5238B_D87Z at 70°C ambient?

At 70 °C ambient, MMBZ5238B_D87Z must be derated linearly from its 350 mW rating at 25 °C, based on a thermal resistance of approximately 357 °C/W (calculated from 350 mW → 150 °C max T_J). This yields ~250 mW maximum continuous dissipation at 70 °C. Exceeding this risks exceeding the 150 °C junction limit, so MMBZ5238B_D87Z should be used with adequate copper area or airflow in elevated-temperature environments.

Is Pin 3 of MMBZ5238B_D87Z electrically connected internally?

No, Pin 3 of MMBZ5238B_D87Z is designated NC (No Connection) and is not electrically connected to any internal structure. Per Fairchild's connection diagram, only Pins 1 (anode) and 2 (cathode) are functional. Soldering or routing to Pin 3 may cause mechanical stress or shorting risk; MMBZ5238B_D87Z must be mounted with Pin 3 left unconnected on the PCB.

How does reverse leakage current behave for MMBZ5238B_D87Z below rated V_R?

For MMBZ5238B_D87Z, reverse leakage current is specified as ≤3.0 µA at V_R = 6.5 V. Below that voltage - e.g., at 5.0 V or 3.0 V - leakage drops exponentially and is typically <0.1 µA, as confirmed by typical characteristic curves in the Fairchild datasheet. This ultra-low sub-threshold leakage makes MMBZ5238B_D87Z suitable for high-impedance reference nodes where even nanoamp-level currents would induce error.