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STMicroelectronics BU808DFI
- Part No.:
- BU808DFI
- Manufacturer:
- STMicroelectronics
- Category:
- Single Bipolar Transistors
- Package:
- ISOWATT-218-3
- Datasheet:
-
BU808DFI.pdf
- Description:
- TRANS NPN DARL 700V ISOWATT218
- Quantity:
- Payment:
- Shipping:
Inventory:3,532
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Product details
Overview
BU808DFI from STMicroelectronics is a high-voltage NPN monolithic Darlington transistor with integrated freewheeling diode, rated for 1400 V VCBO and 700 V VCEO, delivering 8 A continuous collector current and typical DC current gain of 150 at 5 A/5 V, designed specifically for horizontal deflection in CRT TVs up to 21 inches.
For engineers reviewing the BU808DFI datasheet, BU808DFI pinout, BU808DFI application, or BU808DFI equivalent, key selection considerations include insulation withstand voltage (2500 V RMS), low base-drive requirements, storage/fall time performance under inductive 16 kHz switching, and thermal resistance (2.4 °C/W junction-to-case).
Technical Context
The BU808DFI integrates a freewheeling diode monolithically within a Darlington pair structure fabricated using Multiepitaxial Mesa technology, enabling high-voltage blocking (>1400 V) while maintaining low saturation voltages (VCE(sat) = 1.6 V at 5 A/0.5 A). Its fully insulated ISOWATT218 package eliminates need for insulating washers during heatsink mounting.
Switching behavior is optimized for CRT horizontal deflection: storage time (ts) is 3 µs and fall time (tf) is 0.8 µs at 16 kHz with inductive load, and negative base drive (IB2) is critical to minimize turn-off losses and avoid tailing in collector current due to carrier recombination dynamics.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO | 1400 V - enables safe operation in CRT flyback circuits with high voltage transients |
| VCEO | 700 V - defines maximum collector-emitter blocking voltage under open-base condition |
| IC (continuous) | 8 A - supports sustained horizontal deflection current in 21-inch TV applications |
| hFE (typ.) | 150 at IC = 5 A, VCE = 5 V - reduces required base drive current for saturation |
| Visol (RMS) | 2500 V - UL-compliant insulation allows direct mounting to grounded heatsink without isolation hardware |
| Rthj-case | 2.4 °C/W - enables 52 W power dissipation at Tc = 25 °C with manageable junction temperature rise |
| VF (diode) | 3 V at IF = 5 A - integrated freewheeling diode handles inductive energy recovery with known forward drop |
Pinout & Package
The BU808DFI is housed in an ISOWATT218 package - a fully insulated, through-hole power package with three leads and integral heatsink interface compliant with UL insulation standards. Mounting torque must not exceed 1 Nm; flatness tolerance on heatsink side is 80 µm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Collector) | Main power output node | Connected to flyback transformer primary; carries full horizontal deflection current and withstands 1400 V transient spikes |
| 2 (Base) | Control input for Darlington pair | Receives positive IB1 for saturation and negative IB2 for fast turn-off; dual-polarity drive minimizes switching losses |
| 3 (Emitter) | Power return path | Common emitter node shared by Darlington and integrated diode; referenced to ground or damper circuit |
Key Features
| Feature | Design Value |
|---|---|
| Integrated freewheeling diode | Monolithic 3 V / 5 A diode eliminates external component count and layout parasitics in deflection snubber networks |
| UL-compliant insulation | 2500 V RMS isolation between all three leads and heatsink enables simplified mechanical assembly and reduced BOM cost |
| Low VCE(sat) | 1.6 V at 5 A/0.5 A reduces conduction loss and thermal stress during active scan period |
| Optimized 16 kHz switching | 3 µs storage time and 0.8 µs fall time support stable horizontal retrace timing without overshoot or ringing |
Applications
| Horizontal Deflection in CRT TVs | Monitor Flyback Circuits |
|---|---|
Use Scenario: Horizontal scanning in 14–21 inch CRT televisions requiring precise 15.625 kHz timing and high-voltage flyback recovery. IC Role / Device Role / Timing Role: Main switch in line-output stage; controls primary current flow and enables energy transfer to secondary via flyback transformer. Use Value: Integrated diode and 1400 V VCBO ensure reliable flyback voltage clamping without external snubbers, reducing component count and board space. | Use Scenario: Compact CRT monitors needing robust deflection switching with minimal thermal derating at ambient temperatures up to 70 °C. IC Role / Device Role / Timing Role: High-side power switch in self-oscillating or synchronized horizontal output stages. Use Value: 2.4 °C/W Rthj-case and 52 W Ptot allow stable operation without forced cooling, lowering system cost and noise. |
| Legacy Display Repair | Industrial CRT-Based Instruments |
Use Scenario: Replacement part for discontinued horizontal output transistors in service centers repairing older TV chassis (e.g., Philips, Grundig, Panasonic). IC Role / Device Role / Timing Role: Direct-fit Darlington replacement with identical pinout and insulation rating. Use Value: UL-rated insulation and ISOWATT218 footprint ensure drop-in compatibility and safety compliance without redesign. | Use Scenario: Oscilloscopes, radar displays, and medical imaging CRTs requiring long-term reliability and consistent switching waveform fidelity. IC Role / Device Role / Timing Role: Critical timing switch in high-reliability deflection systems where parameter drift must be minimized over 10+ years. Use Value: Stable hFE (60–230 range) and low ICES (400 µA max) ensure predictable turn-on threshold and leakage control across temperature extremes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage Darlington deflection transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BU2520DX | Higher VCEO (1000 V), lower hFE (min. 30), no integrated diode | Requires external freewheeling diode; suited for higher-power 25-inch designs | Select when higher voltage margin is needed and board space permits discrete diode placement |
| 2SD1555 | Lower VCBO (1200 V), same ISOWATT218 package, no integrated diode | Lacks monolithic diode; demands careful snubber design for flyback energy management | Choose only if legacy design already includes optimized external clamp network |
Compared with BU2520DX and 2SD1555, the BU808DFI uniquely combines 1400 V VCBO, integrated diode, and UL-rated insulation - making it the only option that satisfies full safety, space, and timing requirements for cost-sensitive 21-inch TV deflection without external components or mounting isolation.
Availability
BU808DFI is available at Aetrix Electronics and suitable for CRT television manufacturing, display repair services, and industrial instrumentation requiring stable component supply with long-lifecycle support and traceable sourcing.
Supply support for BU808DFI 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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.
The BU808DFI belongs to ST's high-voltage power transistor product line, engineered specifically for cost-effective, reliable horizontal deflection in analog CRT display systems with stringent safety and thermal constraints.
FAQ
What is the maximum safe operating frequency for BU808DFI in horizontal deflection?
The BU808DFI is characterized and validated for stable operation at 16 kHz, matching standard CRT horizontal scan rates (e.g., 15.625 kHz). Its 3 µs storage time and 0.8 µs fall time are measured under inductive load at this frequency; operation beyond 16 kHz risks increased switching losses and thermal runaway due to insufficient carrier recombination time.
Can BU808DFI be used without a heatsink?
No. With a maximum power dissipation of 52 W and junction-to-case thermal resistance of 2.4 °C/W, even brief operation at full load without heatsinking would exceed the 150 °C maximum junction temperature within seconds. A properly mounted heatsink with thermal interface material is mandatory for continuous duty in deflection applications.
Is the integrated diode electrically isolated from the transistor die?
Yes - the freewheeling diode is monolithically integrated but shares no electrical connection with the Darlington emitter or collector except through the defined anode (connected to collector) and cathode (connected to emitter) terminals. Its 3 V forward voltage and 5 A rating are specified independently in the datasheet under IF = 5 A test conditions.
Does BU808DFI require negative base drive during turn-off?
Yes. Application Note AN1184 explicitly specifies that a controlled negative base current (IB2) is essential to rapidly remove stored charge and minimize fall time and turn-off power loss. Without negative drive, tailing current and excessive junction heating occur - especially critical during the retrace phase of CRT horizontal deflection.
BU808DFI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- ISOWATT-218-3
- Packaging:
- Tube
- Product Status:
- Obsolete
- Transistor Type:
- NPN - Darlington
- Current - Collector (Ic) (Max):
- 8 A
- Voltage - Collector Emitter Breakdown (Max):
- 700 V
- Vce Saturation (Max) @ Ib, Ic:
- 1.6V @ 500mA, 5A
- Current - Collector Cutoff (Max):
- 400µA
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 60 @ 5A, 5V
- Power - Max:
- 52 W
- Frequency - Transition:
- -
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- ISOWATT-218
BU808DFI FAQ
1.How can I place an order for BU808DFI through Aetrix?
Please submit a Request for Quotation (RFQ) for BU808DFI 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 BU808DFI reliable?
The price and inventory of BU808DFI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU808DFI is usually 5 days.
3.What payment methods are accepted for BU808DFI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU808DFI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BU808DFI?
BU808DFI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BU808DFI 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 BU808DFI?
For technical support, including BU808DFI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU808DFI requirements.
6.How does Aetrix verify that BU808DFI is sourced from the original manufacturer or authorized distributors?
All BU808DFI 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 BU808DFI meets industry standards.
7.What is the process for return or replacement of BU808DFI?
All BU808DFI units undergo pre-shipment inspection (PSI). If there is an issue with BU808DFI, 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 BU808DFI part is unused and in its original packaging.
Return procedure for BU808DFI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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