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onsemi MMBZ5257B
- Part No.:
- MMBZ5257B
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
MMBZ5257B.pdf
- Description:
- DIODE ZENER 33V 300MW SOT23
- Quantity:
- Payment:
- Shipping:
Inventory:27,000
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Product details
Overview
MMBZ5257B from Fairchild Semiconductor is a 33 V ±5% Zener diode in SOT-23 package, rated for 250 mW power dissipation at 25°C ambient, with 3.8 Ω dynamic impedance at 42 mA test current and 0.1 μA reverse leakage at 25.2 V, used for precision voltage regulation and overvoltage protection in low-power analog circuits.
For engineers reviewing the MMBZ5257B datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage tolerance, dynamic impedance at specified test current, thermal resistance (RθJA = 465°C/W), reverse leakage at rated VR, and SOT-23 footprint compatibility with space-constrained PCB layouts.
Technical Context
The MMBZ5257B operates as a silicon planar Zener diode optimized for stable voltage reference and clamping in DC bias networks. Its 33 V nominal breakdown voltage is specified at IZ = 42 mA with ±5% tolerance, and it maintains low dynamic impedance (3.8 Ω) under that condition to minimize regulation error across load variations.
Thermal performance is defined by RθJA = 465°C/W on FR-4 PCB (76.2 mm × 114.3 mm), limiting continuous power handling to 250 mW at TA = 25°C. Forward voltage is capped at 0.9 V at IF = 10 mA, supporting bidirectional transient suppression when paired with another diode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 33 V nominal, min 31.35 V / max 34.65 V at IZ = 42 mA - defines precise clamping threshold for overvoltage protection |
| Zener Impedance (ZZ) | 3.8 Ω at IZ = 42 mA - ensures tight voltage regulation under varying load current |
| Power Dissipation (PD) | 250 mW at TA = 25°C - sets maximum continuous DC power in standard PCB layout |
| Reverse Leakage (IR) | 0.1 μA at VR = 25.2 V - guarantees minimal standby current in high-impedance bias networks |
| Junction-to-Ambient RθJA | 465°C/W - determines temperature rise per milliwatt; requires derating above 25°C ambient |
| Forward Voltage (VF) | ≤0.9 V at IF = 10 mA - enables use in low-voltage clamp configurations with predictable turn-on |
Pinout & Package
SOT-23 plastic surface-mount package with cathode-marked lead configuration; standardized 3-pin footprint (anode, cathode, NC) per Fairchild connection diagram.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Anode | Connected to lower-potential node in reverse-biased Zener operation; forward conduction path when VF applied |
| 2 | No Connect | Internal die pad not electrically connected; no routing or soldering required |
| 3 | Cathode | Connected to higher-potential node; marked side of package; primary heat path via ψJL = 220°C/W |
Key Features
| Feature | Design Value |
|---|---|
| ±5% Zener voltage tolerance | Enables accurate voltage reference without post-production trimming in cost-sensitive designs |
| Low dynamic impedance (3.8 Ω) | Reduces output voltage deviation under load transients in feedback or bias networks |
| 0.1 μA reverse leakage at 76% VR | Preserves signal integrity in high-impedance sensor interfaces and battery-powered circuits |
| SOT-23 footprint compatibility | Supports automated placement and reflow in high-density consumer electronics PCBs |
Applications
| Industrial Sensor Signal Conditioning | USB Port Overvoltage Protection |
|---|---|
Use Scenario: Stabilizing reference voltage for 12-bit ADC front-end in temperature transmitter modules operating from 24 V loop supply. IC Role / Device Role / Timing Role: Zener diode providing 33 V regulated rail for op-amp bias and ADC reference buffer. Use Value: Tight 31.35–34.65 V tolerance and 3.8 Ω impedance ensure <±2 LSB error contribution across 0–70°C ambient range. | Use Scenario: Clamping induced ESD transients on USB D+ line during hot-plug events in embedded host controllers. IC Role / Device Role / Timing Role: Standalone Zener clamp shunting >25 V spikes to ground before reaching PHY interface. Use Value: 0.1 μA leakage at 25.2 V prevents false signaling during idle bus states; SOT-23 fits adjacent to USB connector. |
| Programmable Logic Controller I/O Protection | DC-DC Converter Feedback Divider Reference |
Use Scenario: Protecting 24 V digital input channels against field-wiring faults and inductive kickback in factory automation PLCs. IC Role / Device Role / Timing Role: Primary overvoltage clamp limiting input node to ≤34.65 V during surge events. Use Value: 250 mW rating sustains 100 ms surge pulses per IEC 61000-4-5 Level 3; RθJA allows thermal recovery between events. | Use Scenario: Providing stable voltage reference point for resistor divider network setting output voltage of isolated flyback converter. IC Role / Device Role / Timing Role: Precision Zener establishing fixed node in feedback loop to improve output regulation accuracy. Use Value: 3.8 Ω ZZ minimizes load-induced drift in divider current, improving line/load regulation to ±1.2% over full operating range. |
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 nominal, ±5% tolerance, but 300 mW PD and 60 Ω ZZ at 5 mA - higher impedance, lower test current | Less suitable for low-drift regulation; better for simple clamping where leakage <1 μA suffices | Select BZX84-C33 only if board layout permits larger thermal mass or if 5 mA test condition aligns with system bias current |
| MMBZ5257BS | Same electrical specs but SOD-323 package - 1.3 mm × 0.85 mm vs. SOT-23's 2.9 mm × 1.3 mm; identical pinout orientation | Enables further miniaturization but requires requalification of solder joint reliability and thermal performance | Choose MMBZ5257BS only when PCB area is constrained below SOT-23 footprint and thermal margin remains ≥15°C |
Compared with BZX84-C33 and MMBZ5257BS, the MMBZ5257B delivers superior regulation stability (3.8 Ω vs. 60 Ω) at higher test current, while maintaining industry-standard SOT-23 assembly compatibility - making it optimal for precision bias and mid-power clamping where thermal and impedance performance are prioritized.
Availability
MMBZ5257B is available at Aetrix Electronics and suitable for industrial sensor conditioning, USB port protection, and PLC I/O protection requiring stable component supply, consistent parametric performance, and long-term obsolescence management.
Supply support for MMBZ5257B 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 and manufacturer of analog and discrete semiconductors, acquired by ON Semiconductor in 2016; known for high-reliability power and signal conditioning components.
The MMBZ52xxB series was developed for general-purpose voltage regulation and transient suppression in commercial-grade consumer and industrial electronics, emphasizing SOT-23 manufacturability and parametric consistency across the 2.4–33 V range.
FAQ
What is the Zener voltage tolerance of the MMBZ5257B?
The MMBZ5257B has a Zener voltage tolerance of ±5%, meaning its breakdown voltage ranges from 31.35 V to 34.65 V when tested at 42 mA. This tolerance is guaranteed across manufacturing lots and supports repeatable circuit design without calibration. The MMBZ5257B achieves this specification using planar diffusion process control, and the value is verified per Rev. 1.5 datasheet test conditions at TA = 25°C.
Can the MMBZ5257B be used in place of a 30 V Zener diode?
No, the MMBZ5257B is not a drop-in replacement for a 30 V Zener diode because its nominal Zener voltage is 33 V with a minimum of 31.35 V - exceeding the 30 V rating by at least 1.35 V. Substituting the MMBZ5257B would raise clamping or regulation thresholds, potentially causing overvoltage stress on downstream components. Always verify target voltage alignment before substitution; the MMBZ5257B is intended specifically for 33 V applications.
What is the maximum reverse leakage current for the MMBZ5257B?
The maximum reverse leakage current for the MMBZ5257B is 0.1 μA at VR = 25.2 V (76% of nominal VZ), as specified in the Electrical Characteristics table. This ultra-low leakage ensures minimal current draw in high-impedance bias networks and preserves accuracy in precision analog circuits. The MMBZ5257B maintains this spec across its qualified temperature range and is measured under controlled 25°C ambient conditions.
Does the MMBZ5257B have a specified forward voltage?
Yes, the MMBZ5257B has a maximum forward voltage (VF) of 0.9 V at IF = 10 mA, consistent across the entire MMBZ5200 series. This parameter is relevant when the device is forward-biased - for example, in dual-diode transient suppressor configurations or polarity-protection circuits. The MMBZ5257B's VF is guaranteed per datasheet Section 3 and applies to the anode-to-cathode conduction path under DC conditions.
Is the MMBZ5257B RoHS compliant?
Yes, the MMBZ5257B is RoHS compliant per the original Fairchild Semiconductor documentation and ON Semiconductor's post-acquisition product continuity records. It contains no lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE) above threshold limits. Compliance is confirmed for both the SOT-23 package and internal die construction, and the MMBZ5257B meets JEDEC J-STD-609A marking requirements for lead-free finish.
MMBZ5257B Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-236-3, SC-59, SOT-23-3
- Packaging:
- Bulk
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 33 V
- Tolerance:
- ±5%
- Power - Max:
- 300 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:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23
MMBZ5257B FAQ
1.How can I place an order for MMBZ5257B through Aetrix?
Please submit a Request for Quotation (RFQ) for MMBZ5257B 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 reliable?
The price and inventory of MMBZ5257B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMBZ5257B is usually 5 days.
3.What payment methods are accepted for MMBZ5257B?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMBZ5257B transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MMBZ5257B?
MMBZ5257B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MMBZ5257B 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?
For technical support, including MMBZ5257B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMBZ5257B requirements.
6.How does Aetrix verify that MMBZ5257B is sourced from the original manufacturer or authorized distributors?
All MMBZ5257B 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 meets industry standards.
7.What is the process for return or replacement of MMBZ5257B?
All MMBZ5257B units undergo pre-shipment inspection (PSI). If there is an issue with MMBZ5257B, 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 part is unused and in its original packaging.
Return procedure for MMBZ5257B:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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