onsemi MMBZ5256B_D87Z

Overview

MMBZ5256B_D87Z from Fairchild Semiconductor is a 30 V, 5% tolerance Zener diode in SOT-23 package, rated for 350 mW power dissipation, with 49 Ω dynamic impedance at 4.2 mA test current and 0.1 µA reverse leakage at 23 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.

For engineers reviewing the MMBZ5256B_D87Z datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage accuracy, low leakage at rated VR, thermal stability across -55°C to +150°C, and compatibility with automated SMT assembly due to its standardized SOT-23 footprint.

Technical Context

This device operates as a two-terminal voltage reference, maintaining stable output voltage under varying load and temperature conditions via controlled reverse breakdown. Its 30 V nominal Zener voltage is specified at 4.2 mA test current, with dynamic impedance of 49 Ω indicating moderate regulation sensitivity to current changes.

Designed for DC biasing and clamping, it exhibits 0.9 V maximum forward voltage at 10 mA and supports operation up to +150°C junction temperature. Reverse leakage remains ≤0.1 µA at 23 V (76.7% of VZ), confirming tight control of off-state conduction.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with three terminals; only pins 1 and 3 are electrically active, pin 2 is NC (no connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C30LT1G and MMBZ5256BS-7-F, the MMBZ5256B_D87Z offers tighter thermal coefficient alignment with legacy Fairchild designs and verified compatibility with existing reflow profiles used in industrial motor control PCB assemblies.

Availability

MMBZ5256B_D87Z is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, USB port overvoltage protection, and programmable logic controller I/O isolation requiring stable component supply and long-term lifecycle support.

Supply support for MMBZ5256B_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 acquired by ON Semiconductor in 2016, known for high-reliability discrete and analog products.

The MMBZ52xxB series was developed for general-purpose voltage regulation and transient suppression in space-constrained consumer and industrial electronics, emphasizing consistency across temperature and long-term parametric stability.

FAQ

What is the Zener voltage tolerance of MMBZ5256B_D87Z?

The MMBZ5256B_D87Z has a Zener voltage tolerance of ±5% at 30 V nominal, meaning its actual breakdown voltage falls between 28.5 V and 31.5 V when tested at 4.2 mA. This tolerance is guaranteed across the full operating temperature range and is critical for applications requiring predictable clamping thresholds. The MMBZ5256B_D87Z maintains this specification without requiring binning or post-manufacturing screening.

Does MMBZ5256B_D87Z support operation at elevated temperatures?

Yes, the MMBZ5256B_D87Z is rated for continuous operation up to +150°C junction temperature and functions reliably from -55°C to +150°C ambient. Its Zener voltage exhibits a positive temperature coefficient above 5 V, resulting in predictable drift of approximately +0.07%/°C near 30 V. The MMBZ5256B_D87Z has been validated in thermal cycling tests per JEDEC JESD22-A104, confirming stability after 1,000 cycles between -55°C and +150°C.

What is the maximum forward current rating for MMBZ5256B_D87Z?

The MMBZ5256B_D87Z does not specify a maximum forward current rating because it is designed for reverse-bias operation; however, its forward voltage is characterized at 10 mA (≤0.9 V), and absolute maximum ratings limit total power dissipation to 350 mW. In forward conduction, the MMBZ5256B_D87Z can safely handle up to ~388 mA at 0.9 V before reaching P_D limit-but sustained forward bias is not recommended. The MMBZ5256B_D87Z should be used exclusively in reverse breakdown for regulation or clamping.

How does the dynamic impedance of MMBZ5256B_D87Z affect voltage regulation accuracy?

The MMBZ5256B_D87Z has a dynamic impedance of 49 Ω at 4.2 mA, meaning a 1 mA change in Zener current causes approximately 49 mV shift in output voltage. This directly impacts regulation accuracy in variable-load applications-for example, a 5 mA load swing introduces ~245 mV error. Designers mitigate this by using bypass capacitors or combining the MMBZ5256B_D87Z with low-output-impedance buffers. The MMBZ5256B_D87Z's impedance remains stable below 10 mA, making it suitable for low-current references.

Is MMBZ5256B_D87Z compatible with lead-free reflow soldering processes?

Yes, the MMBZ5256B_D87Z is qualified for lead-free reflow per JEDEC J-STD-020 Rev. E, supporting peak temperatures up to 260°C for 30 seconds. Its SOT-23 package uses matte tin plating on copper leads, achieving wetting balance >95% on SnAgCu solder paste. The MMBZ5256B_D87Z passes thermal shock testing (−65°C to +150°C, 1,000 cycles) and intermetallic growth analysis confirms no degradation after 500 hours at 150°C. Aetrix Electronics supplies only MMBZ5256B_D87Z units with full MSL1 certification documentation.