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onsemi MMBZ5238B
- Part No.:
- MMBZ5238B
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
MMBZ5238B.pdf
- Description:
- DIODE ZENER 8.7V 350MW SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:9,879
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Product details
Overview
MMBZ5238B from Fairchild Semiconductor is a 5% tolerance, 8.7V Zener diode in SOT-23 package, rated for 350mW power dissipation, with 8Ω dynamic impedance at 20mA test current and 3.0µA reverse leakage at 6.5V, used for voltage regulation and overvoltage protection in low-power analog circuits.
For engineers reviewing the MMBZ5238B 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 existing PCB layouts.
Technical Context
The MMBZ5238B operates as a silicon planar epitaxial Zener diode optimized for stable voltage reference and clamping functions in space-constrained DC bias networks. Its 8.7V nominal breakdown voltage is specified at 20mA test current with ±5% tolerance, and it maintains regulated output under reverse-biased conditions across -55°C to +150°C junction temperature range.
It exhibits 8Ω dynamic impedance (ZZ) at IZ = 20mA and 600Ω knee impedance (ZZK) at IZK = 0.25mA, supporting precise regulation in low-current feedback paths. Forward voltage is capped at 0.9V @ IF = 10mA, enabling bidirectional transient suppression when paired with complementary devices.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage VZ | 8.7V ±5% at IZ = 20mA - defines stable regulation point for reference or clamp circuits |
| Dynamic Impedance ZZ | 8Ω @ IZ = 20mA - determines voltage deviation under load current variation |
| Knee Impedance ZZK | 600Ω @ IZK = 0.25mA - indicates onset of regulation at low bias currents |
| Reverse Leakage IR | 3.0µA @ VR = 6.5V - sets minimum quiescent current in high-impedance sensing nodes |
| Power Dissipation PD | 350mW @ TA = 25°C - limits continuous thermal stress in SOT-23 footprint |
| Forward Voltage VF | ≤0.9V @ IF = 10mA - enables use in bidirectional ESD/clamp configurations |
| Junction Temp TJ | +150°C maximum - supports operation in automotive under-hood and industrial control environments |
Pinout & Package
MMBZ5238B is housed in a standard SOT-23 surface-mount package with three terminals: anode (Pin 1), cathode (Pin 2), and no-connect (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-bias regulation or clamping configuration |
| Pin 2 | Cathode | Connects to higher-potential node; polarity-sensitive terminal for Zener conduction |
| Pin 3 | No Connect (NC) | Internally isolated; must not be soldered or tied to any net on PCB |
Key Features
| Feature | Design Value |
|---|---|
| ±5% Zener voltage tolerance | Enables predictable regulation without post-production trimming in cost-sensitive consumer power rails |
| 8Ω dynamic impedance @ 20mA | Minimizes output voltage shift under ±5mA load transients in sensor biasing networks |
| 3.0µA reverse leakage @ 6.5V | Preserves accuracy in high-impedance voltage divider references for ADC input scaling |
| SOT-23 footprint | Supports automated placement and reflow in compact portable electronics with <2mm² board area |
| 150°C max junction temperature | Allows deployment in thermally demanding locations such as DC-DC converter feedback loops |
Applications
| Industrial Sensor Biasing | USB Port Overvoltage Clamp |
|---|---|
Use Scenario: Providing stable 8.7V reference for precision RTD or thermocouple signal conditioning circuits in programmable logic controllers. IC Role / Device Role / Timing Role: Zener voltage reference and current-limiting element in op-amp bias network. Use Value: Maintains ±0.435V regulation window across temperature, ensuring <0.1% gain error in analog front-end amplification. | Use Scenario: Clamping VBUS line against transient surges during hot-plug events in USB 2.0 peripheral designs. IC Role / Device Role / Timing Role: Reverse-biased shunt protector limiting peak voltage to 8.7V before TVS activation. Use Value: Absorbs up to 350mW surge energy while holding downstream 5V regulator input within safe operating margin. |
| Low-Power Microcontroller Reset Circuit | Automotive Cabin Control Panel Reference |
Use Scenario: Generating clean reset threshold for 3.3V microcontrollers using resistor-divider + Zener topology. IC Role / Device Role / Timing Role: Precision voltage threshold detector in RC-based power-on reset generator. Use Value: Delivers repeatable 8.7V trigger point with <±0.2V drift over -40°C to +85°C ambient range. | Use Scenario: Supplying regulated bias to touch-sensing ICs and LED drivers in vehicle infotainment bezels. IC Role / Device Role / Timing Role: Local voltage reference stabilizing analog supply rail for capacitive touch controller. Use Value: Enables consistent touch sensitivity across 12V battery variations (9–16V) and engine cranking dips. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BZX84-C8V2 | 8.2V nominal VZ, same SOT-23 package, 10Ω ZZ @ 5mA, 100nA IR @ 6.5V | Lower regulation voltage; tighter leakage spec but higher dynamic impedance at low current | Select when lower reference voltage and ultra-low standby leakage outweigh impedance trade-off |
| MMBZ5237B | 8.2V nominal VZ, identical family specs except VZ and ZZ (7Ω @ 20mA) | Near-identical thermal and packaging behavior; differs only in regulation setpoint | Choose for systems requiring 8.2V instead of 8.7V without layout or thermal redesign |
Compared with BZX84-C8V2 and MMBZ5237B, the MMBZ5238B offers the highest regulation voltage (8.7V) among these three, lowest dynamic impedance at 20mA (8Ω), and moderate leakage (3.0µA), making it optimal for mid-voltage reference stability where 8.2–8.7V range is acceptable.
Availability
MMBZ5238B is available at Aetrix Electronics and suitable for industrial sensor biasing, USB port overvoltage clamp, and low-power microcontroller reset circuits requiring stable component supply and long-term lifecycle support.
Supply support for MMBZ5238B 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 MMBZ52xxB series was designed for general-purpose voltage regulation and transient suppression in space-constrained, low-power electronic systems across consumer, industrial, and automotive segments.
FAQ
What is the nominal Zener voltage and tolerance of the MMBZ5238B?
The MMBZ5238B has a nominal Zener voltage of 8.7V with a ±5% tolerance, measured at a test current of 20mA. This means the actual breakdown voltage falls between 8.265V and 9.135V under standard conditions. The MMBZ5238B maintains this specification across its full operating temperature range and is validated per Fairchild's Rev. A2 datasheet for the MMBZ5221B–MMBZ5257B family.
What is the maximum power dissipation rating for the MMBZ5238B?
The MMBZ5238B is rated for 350mW maximum power dissipation at 25°C ambient temperature. Derating is required above 25°C - typically linear at 2.86mW/°C - to maintain junction temperature ≤150°C. This rating applies to the SOT-23 package and assumes adequate PCB copper area for heat spreading. The MMBZ5238B must not exceed this limit in continuous operation to ensure reliability.
Does the MMBZ5238B have a no-connect pin, and how should it be handled on the PCB?
Yes, the MMBZ5238B has a no-connect (NC) terminal at Pin 3, as confirmed in the official connection diagram. Pin 3 is internally unconnected and must remain electrically floating - it must not be soldered to ground, VCC, or any other net. Incorrect routing of Pin 3 may cause assembly defects or functional anomalies. The MMBZ5238B's SOT-23 pinout is Anode (Pin 1), Cathode (Pin 2), NC (Pin 3).
What is the reverse leakage current specification for the MMBZ5238B?
The MMBZ5238B specifies a maximum reverse leakage current (IR) of 3.0µA at VR = 6.5V, measured at 25°C. This parameter reflects the diode's ability to block current below its Zener knee and is critical for high-impedance reference applications. The MMBZ5238B maintains this leakage performance across its storage temperature range (-55°C to +150°C), with typical values decreasing at lower temperatures.
Can the MMBZ5238B be used in forward-bias applications?
Yes, the MMBZ5238B can conduct in forward bias with a maximum forward voltage (VF) of 0.9V at IF = 10mA, as specified for the entire MMBZ5200 series. While primarily designed for reverse-bias Zener operation, this forward characteristic allows use in bidirectional protection schemes or polarity-insensitive clamp configurations. However, the MMBZ5238B is not optimized for continuous forward conduction and should not replace dedicated rectifier diodes in power-path roles.
MMBZ5238B 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):
- 8.7 V
- Tolerance:
- ±5%
- Power - Max:
- 350 mW
- Impedance (Max) (Zzt):
- 8 Ohms
- Current - Reverse Leakage @ Vr:
- 3 µA @ 6.5 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
MMBZ5238B FAQ
1.How can I place an order for MMBZ5238B through Aetrix?
Please submit a Request for Quotation (RFQ) for MMBZ5238B 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 MMBZ5238B reliable?
The price and inventory of MMBZ5238B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMBZ5238B is usually 5 days.
3.What payment methods are accepted for MMBZ5238B?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMBZ5238B transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MMBZ5238B?
MMBZ5238B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MMBZ5238B 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 MMBZ5238B?
For technical support, including MMBZ5238B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMBZ5238B requirements.
6.How does Aetrix verify that MMBZ5238B is sourced from the original manufacturer or authorized distributors?
All MMBZ5238B 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 MMBZ5238B meets industry standards.
7.What is the process for return or replacement of MMBZ5238B?
All MMBZ5238B units undergo pre-shipment inspection (PSI). If there is an issue with MMBZ5238B, 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 MMBZ5238B part is unused and in its original packaging.
Return procedure for MMBZ5238B:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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