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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics STLD128DNT4

Name: STLD128DNT4
Brand: STMicroelectronics
SKU: STLD128DNT4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STLD128DNT4

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Datasheet:: STLD128DNT4.pdf

Description:: TRANS NPN 400V 4A DPAK

Quantity:: RFQ Add To RFQ list

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Product details

Overview

STLD128DNT4 from STMicroelectronics is a high-voltage fast-switching NPN power transistor in DPAK (TO-252) package, rated for V_CES = 700 V, I_C = 4 A, and P_TOT = 20 W at T_c = 25 °C, with integrated antiparallel collector-emitter diode and t_s = 4.5 µs storage time. It is designed for electronic ballasts and low-power flyback/forward SMPS.

For engineers reviewing the STLD128DNT4 datasheet, STLD128DNT4 pinout, STLD128DNT4 application, or STLD128DNT4 equivalent, key selection factors include its 700 V blocking capability, 20 W thermal dissipation in DPAK, R_thJC = 6.25 °C/W, and verified use in fluorescent lamp ballasts and single-transistor AC-DC converters.

Technical Context

This device uses high-voltage multi-epitaxial planar technology with cellular emitter structure and planar edge termination to simultaneously achieve high switching speed and wide reverse-biased safe operating area (RBSOA). Its integrated freewheel diode has V_F = 2.5 V at I_F = 1 A.

The transistor supports pulse operation up to I_CM = 8 A (t_P < 5 ms) and operates up to T_J = 150 °C, with V_CEO(sus) = 400 V under sustaining conditions and h_FE = 8–24 across I_C = 10 mA to 2 A at V_CE = 5 V.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	700 V - Enables direct interface with 400 VAC rectified bus in universal-input SMPS and ballasts.
I_C	4 A continuous - Supports up to ~60 W output in single-transistor flyback topologies.
P_TOT (DPAK)	20 W at T_c = 25 °C - Requires heatsinking for sustained >5 W dissipation in PCB-mounted applications.
t_s / t_f	4.5 µs / 0.4 µs - Enables switching frequencies up to ~100 kHz with low turn-off loss in hard-switched converters.
V_CE(sat)	1 V max at I_C = 2 A, I_B = 0.4 A - Limits conduction loss to ≤2 W at full load, critical for thermal management.
R_thJC	6.25 °C/W - Defines junction-to-case thermal gradient; requires low-thermal-resistance PCB copper pour for reliability.
V_F (diode)	2.5 V at I_F = 1 A - Provides integrated freewheel path with predictable forward drop and no external diode needed.

Pinout & Package

STLD128DNT4 is housed in a surface-mount DPAK (TO-252) package with exposed drain-connected tab for thermal and electrical connection. Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (tab).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Main current return path	Low-inductance connection point for emitter loop; referenced to ground in common-emitter switch configurations.
Pin 2 (Base)	Control input terminal	Receives drive current (I_B ≤ 2 A peak); requires ≥1.2 V V_BE(sat) to ensure full turn-on.
Pin 3 (Collector / Tab)	High-voltage power input & thermal interface	Electrically connected to collector and thermally coupled to PCB copper; must be isolated from other nets unless used as heat sink.

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates need for external freewheel diode in flyback/forward snubberless designs, reducing BOM count and layout area.
Large RBSOA	Supports reliable operation under inductive switching stress without secondary breakdown, even at high V_CE and moderate I_C.
Low dynamic parameter spread	Ensures consistent switching timing and gain across production lots, simplifying gate driver design and system validation.
ECOPACK®-compliant DPAK	Meets RoHS and halogen-free requirements without compromising thermal performance or manufacturability in reflow assembly.

Applications

Fluorescent Lamp Electronic Ballast

Flyback Converter (≤60 W)

Use Scenario: High-frequency (20–60 kHz) resonant inverter driving 4–80 W T5/T8 lamps with dimming and end-of-life protection.

IC Role / Device Role / Timing Role: Main switching transistor in half-bridge or single-ended topology, handling 350–450 V DC link voltage and delivering regulated lamp current.

Use Value: Integrated diode enables self-oscillating or fixed-frequency control without external clamp; 700 V rating avoids derating in 230 VAC mains applications.

Use Scenario: Universal-input (85–265 VAC), isolated DC-DC supply for smart meters, IoT sensors, and industrial controls.

IC Role / Device Role / Timing Role: Primary-side power switch in discontinuous conduction mode (DCM), synchronized with optocoupler feedback.

Use Value: 4.5 µs storage time allows stable 65–100 kHz operation; 20 W DPAK dissipation supports compact transformer-less heatsink design.

Forward Converter (Low-Power)

LED Driver (Non-Isolated Buck-Boost)

Use Scenario: 24–48 V input, 12 V/3 A output telecom or PoE-powered auxiliary supply with tight regulation.

IC Role / Device Role / Timing Role: Main switch clamped by RCD network; operates in continuous conduction mode (CCM) with duty cycle < 50%.

Use Value: Wide RBSOA prevents failure during transient overloads; V_CEO(sus) = 400 V ensures margin against reflected spike voltages.

Use Scenario: Off-line constant-current LED driver for streetlights or commercial fixtures using buck-boost topology with single-stage PFC.

IC Role / Device Role / Timing Role: High-side switch controlling LED string current via valley-switching control and current-sense resistor.

Use Value: Integrated diode provides natural freewheel path during off-time; 150 °C max junction temperature supports sealed outdoor enclosure operation.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN power transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
STP12NK70ZFP	Zener-protected superjunction MOSFET, 700 V, 12 A, R_DS(on) = 0.55 Ω; no integrated diode.	Requires external fast recovery diode; better efficiency above 50 kHz but higher gate drive complexity.	Prefer for >100 kHz SMPS where conduction loss dominates; avoid if board space prohibits external diode placement.
BU508AF	Through-hole TO-3P NPN, 1500 V, 8 A, slower switching (t_s ≈ 10 µs), no integrated diode.	Limited to ≤30 kHz ballasts; requires larger heatsink due to higher V_CE(sat) and lower P_TOT density.	Only suitable for legacy repair or cost-sensitive through-hole designs; not recommended for new SMT-based lighting products.

Compared with STP12NK70ZFP and BU508AF, STLD128DNT4 offers optimal balance of integration (built-in diode), thermal footprint (DPAK), and switching speed for sub-100 kHz fluorescent and low-power SMPS-without requiring gate drivers or extra diodes, while maintaining robust RBSOA for reliability under surge conditions.

Availability

STLD128DNT4 is available at Aetrix Electronics and suitable for electronic ballasts, flyback converters, forward converters, and non-isolated LED drivers requiring stable component supply and long-term industrial availability.

Supply support for STLD128DNT4 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, specializing in power discrete devices, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

This part belongs to ST's high-voltage bipolar power transistor product line, engineered specifically for cost-sensitive, medium-power lighting and AC-DC conversion systems demanding ruggedness, integration, and proven field reliability.

FAQ

What is the maximum allowable base current for continuous operation?

The absolute maximum base current (I_B) is 2 A continuous, per Table 2. For reliable linear operation and thermal stability, ST recommends limiting I_B to ≤0.4 A when I_C = 2 A to maintain h_FE ≥8 and avoid excessive base power dissipation in the DPAK package.

Can STLD128DNT4 replace STL128DN in TO-220 packages?

No-STLD128DNT4 is a DPAK (TO-252) variant with different thermal resistance (R_thJC = 6.25 °C/W vs. 2.08 °C/W for TO-220), lower P_TOT (20 W vs. 60 W), and distinct PCB footprint. It is not a drop-in replacement; layout and thermal design must be requalified for surface-mount assembly and reduced power handling.

Does the integrated diode support reverse recovery in high-frequency operation?

The integrated diode is a standard PN junction with t_rr not specified in the datasheet; it is optimized for freewheeling-not fast recovery. For >50 kHz operation, external ultrafast diodes (e.g., STTH1R06) are recommended to minimize switching losses and EMI from reverse recovery charge.

What is the minimum required gate/base drive voltage to ensure saturation?

Base-emitter saturation voltage is 1.2–1.3 V at I_C = 1–2 A. To guarantee full saturation and minimize V_CE(sat), apply ≥1.5 V V_BE with sufficient base current (I_B ≥ I_C/10). A 5 V logic-level driver with ≥0.4 A peak current meets this requirement for 2 A collector loads.

STLD128DNT4 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 4 A

Voltage - Collector Emitter Breakdown (Max):: 400 V

Vce Saturation (Max) @ Ib, Ic:: 1V @ 400mA, 2A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 8 @ 2A, 5V

Power - Max:: 20 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DPAK

STLD128DNT4 FAQ

1.How can I place an order for STLD128DNT4 through Aetrix?

Please submit a Request for Quotation (RFQ) for STLD128DNT4 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 STLD128DNT4 reliable?

The price and inventory of STLD128DNT4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STLD128DNT4 is usually 5 days.

3.What payment methods are accepted for STLD128DNT4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STLD128DNT4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STLD128DNT4?

STLD128DNT4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STLD128DNT4 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 STLD128DNT4?

For technical support, including STLD128DNT4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STLD128DNT4 requirements.

6.How does Aetrix verify that STLD128DNT4 is sourced from the original manufacturer or authorized distributors?

All STLD128DNT4 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 STLD128DNT4 meets industry standards.

7.What is the process for return or replacement of STLD128DNT4?

All STLD128DNT4 units undergo pre-shipment inspection (PSI). If there is an issue with STLD128DNT4, 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 STLD128DNT4 part is unused and in its original packaging.

Return procedure for STLD128DNT4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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