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Diodes Incorporated FMMT458TA
- Part No.:
- FMMT458TA
- Manufacturer:
- Diodes Incorporated
- Category:
- Single Bipolar Transistors
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
FMMT458TA.pdf
- Description:
- TRANS NPN 400V 0.225A SOT-23-3
- Quantity:
- Payment:
- Shipping:
Inventory:68,761
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Product details
Overview
FMMT458TA from Diodes Incorporated is a 400V NPN high-voltage transistor in SOT23 package, designed for switching and amplification in high-breakdown-voltage applications. It delivers 225mA continuous collector current, 1A peak pulse current, 500mW power dissipation, and exhibits hFE up to 300 at IC = 100mA, VCE = 10V - used in flyback snubber circuits, relay drivers, and HV DC-DC converter primary-side switches.
For engineers reviewing the FMMT458TA datasheet, FMMT458TA pinout, FMMT458TA application, or FMMT458TA equivalent, key selection criteria include verified 400V VCEO rating, SOT23 thermal performance (RθJA = 250°C/W), safe operating area under pulsed HV conditions, and complementary PNP pairing with FMMT558TA.
Technical Context
This NPN bipolar junction transistor operates with BVCEO and BVCBO rated at 400V, enabling use in off-line switch-mode power supplies where primary-side voltage transients exceed 300V. Its low VCE(sat) of 500mV at IC = 50mA/IB = 6mA supports efficient switching in medium-current HV stages.
The device features JEDEC Class 3A HBM ESD rating (4kV), 7V VEBO limit, and fT = 50MHz - confirming suitability for moderate-speed switching (e.g., <500kHz PWM) rather than RF or high-frequency linear amplification. Thermal derating begins at +25°C ambient, with full 500mW dissipation only on 15mm × 15mm FR-4 PCB with 1oz copper.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 400V - supports direct connection to 340V DC bus (e.g., rectified 240VAC) without external clamping |
| IC (cont.) | 225mA - sufficient for driving small relays, optocoupler LEDs, or gate resistors in <10W SMPS |
| VCE(sat) | 500mV @ IC = 50mA, IB = 6mA - limits conduction loss to ≤25mW in saturated switching mode |
| hFE | 100–300 @ IC = 1–100mA - enables stable current gain across bias range for analog sensing or linear regulation |
| fT | 50MHz - supports clean turn-on/turn-off in 100–300kHz SMPS control loops |
| RθJA | 250°C/W - requires ≥15mm² copper pour for sustained 500mW operation at TA = +25°C |
Pinout & Package
Package: SOT23 - surface-mount plastic package with matte tin-plated leads, moisture sensitivity level 1, UL 94V-0 rated molding compound, weight ≈0.008g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Emitter) | E | Reference node for base drive; connects to ground or low-side return path in common-emitter configuration |
| 2 (Base) | B | Current-controlled input; requires ≥5mA drive for full saturation at IC = 50mA per VBE(sat) = 0.9V spec |
| 3 (Collector) | C | High-voltage output node; handles up to 400V reverse-biased during switching transitions |
Key Features
| Feature | Design Value |
|---|---|
| 400V breakdown rating | Enables direct integration into 230VAC-derived primary-side circuits without series stacking or external TVS |
| Complementary PNP pair (FMMT558TA) | Allows matched push-pull or totem-pole driver design with consistent thermal and gain characteristics |
| Lead-free & halogen-free "Green" construction | Meets RoHS 3 (2015/863/EU), <900ppm Br/Cl, <1000ppm Sb - compliant for automotive and industrial end-equipment |
| JEDEC Class 3A HBM ESD rating | 4kV tolerance reduces risk of assembly-line damage and improves field reliability in unshielded environments |
Applications
| Switch-Mode Power Supply Snubber | Industrial Relay Driver |
|---|---|
|
Use Scenario: Absorbs voltage spikes across MOSFET drains in flyback or forward converters operating from 230VAC mains. IC Role / Device Role / Timing Role: NPN clamp transistor configured in active-clamp or passive snubber topology, triggered by transformer leakage inductance. Use Value: 400V VCEO withstands reflected transient voltages up to 380V, reducing need for Zener clamps or RCD networks. |
Use Scenario: Drives 24V/12V industrial control relays requiring ≥100mA coil current in PLC I/O modules. IC Role / Device Role / Timing Role: Medium-current saturated switch interfacing microcontroller GPIO to relay coil via base resistor network. Use Value: 225mA IC rating and 500mV VCE(sat) ensure <12mW conduction loss at 100mA load, minimizing self-heating on dense PCBs. |
| DC-DC Converter Primary Switch | High-Voltage Signal Level Shifter |
|
Use Scenario: Low-power isolated DC-DC converter (<5W) for sensor biasing in smart metering or grid-edge monitoring. IC Role / Device Role / Timing Role: Primary-side switching element in self-oscillating or fixed-frequency flyback topology with discrete controller. Use Value: 50MHz fT and 2260ns toff support stable 250kHz operation with minimal switching loss and overshoot. |
Use Scenario: Translates logic-level signals (3.3V/5V) to 100–300V domains for status feedback or fault reporting in HV battery management systems. IC Role / Device Role / Timing Role: Common-emitter level translator with emitter grounded, collector pulled to HV rail via load resistor. Use Value: 400V BVCEO and 100nA ICES at VCE = 320V ensure signal integrity and leakage immunity in >300V floating domains. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage NPN transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ZTX458 | VCEO = 300V (lower), hFE min = 100 @ IC = 10mA, same SOT23 package | Not suitable for 340V DC bus designs; limited to ≤250V applications | Select only when system max VCE < 280V and cost sensitivity outweighs voltage margin |
| MMBT4401 | VCEO = 40V (drastically lower), IC = 600mA, fT = 250MHz | Designed for low-voltage, high-speed switching - incompatible with HV supply rails | Reject for any application requiring >100V collector swing; not a functional substitute |
Compared with ZTX458 and MMBT4401, FMMT458TA uniquely balances 400V ruggedness, SOT23 footprint, and 225mA current capability - making it the only viable choice among these three for off-line auxiliary supplies and HV interface circuits.
Availability
FMMT458TA is available at Aetrix Electronics and suitable for industrial power conversion, HV sensor interfaces, and programmable logic controller (PLC) output stages requiring stable component supply and long-term manufacturability.
Supply support for FMMT458TA 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
Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.
FMMT458TA belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for reliable switching in off-line AC/DC power supplies, industrial controls, and HV interface circuits where breakdown voltage and thermal robustness are critical.
FAQ
What is the maximum safe operating voltage for FMMT458TA in continuous DC mode?
The FMMT458TA is rated for VCEO = 400V and VCB0 = 400V under DC conditions at TA = +25°C. Derating applies above +25°C ambient: maximum VCEO decreases linearly to ~280V at +100°C case temperature. Operation must remain within the Safe Operating Area (SOA) curve shown in Figure 1 of DS33088 Rev. 8-2, especially under pulsed loads.
Can FMMT458TA replace a MOSFET in high-voltage switching applications?
No - FMMT458TA is a bipolar transistor requiring continuous base current for saturation, unlike voltage-driven MOSFETs. Its 500mW power limit and 225mA IC rating make it unsuitable for high-efficiency, high-current switching. It serves best in low-to-medium power, cost-sensitive HV roles where gate-drive complexity must be avoided.
Is FMMT458TA suitable for automotive applications?
The standard FMMT458TA is not AEC-Q101 qualified. However, Diodes offers the automotive-compliant FMMT458Q variant (separate datasheet), which undergoes stress testing per AEC-Q101 and supports extended temperature operation. Use FMMT458Q - not FMMT458TA - in automotive ECUs or ADAS power stages.
How does the SOT23 package affect thermal performance in real-world PCB layouts?
Rated RθJA = 250°C/W assumes mounting on 15mm × 15mm FR-4 with 1oz copper. On typical 4-layer boards with limited copper, RθJA degrades to ~350°C/W. To sustain 500mW, add ≥25mm² thermal pad connected to internal ground plane via ≥4 vias, and avoid placing near heat sources like transformers or bridge rectifiers.
FMMT458TA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diodes Incorporated
- Series:
- -
- Package/Case:
- TO-236-3, SC-59, SOT-23-3
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 225 mA
- Voltage - Collector Emitter Breakdown (Max):
- 400 V
- Vce Saturation (Max) @ Ib, Ic:
- 500mV @ 6mA, 50mA
- Current - Collector Cutoff (Max):
- 100nA
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 100 @ 50mA, 10V
- Power - Max:
- 500 mW
- Frequency - Transition:
- 50MHz
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-3
FMMT458TA FAQ
1.How can I place an order for FMMT458TA through Aetrix?
Please submit a Request for Quotation (RFQ) for FMMT458TA 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 FMMT458TA reliable?
The price and inventory of FMMT458TA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FMMT458TA is usually 5 days.
3.What payment methods are accepted for FMMT458TA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FMMT458TA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FMMT458TA?
FMMT458TA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FMMT458TA 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 FMMT458TA?
For technical support, including FMMT458TA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FMMT458TA requirements.
6.How does Aetrix verify that FMMT458TA is sourced from the original manufacturer or authorized distributors?
All FMMT458TA 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 FMMT458TA meets industry standards.
7.What is the process for return or replacement of FMMT458TA?
All FMMT458TA units undergo pre-shipment inspection (PSI). If there is an issue with FMMT458TA, 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 FMMT458TA part is unused and in its original packaging.
Return procedure for FMMT458TA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
FMMT458TA Tags
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