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Diotec Semiconductor DB3
- Part No.:
- DB3
- Manufacturer:
- Diotec Semiconductor
- Category:
- DIACs, SIDACs
- Package:
- DO-204AH, DO-35, Axial
- Datasheet:
-
DB3.pdf
- Description:
- DIAC DO-35 28V 36V
- Quantity:
- Payment:
- Shipping:
Inventory:4,890
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Product details
Overview
DB3 from STMicroelectronics is a bidirectional trigger diode (DIAC) with 28–36 V breakover voltage range, low 50 µA breakover current, and ±3 V symmetry in forward/reverse conduction. It functions as a voltage-controlled switch to initiate gate firing of triacs/SCRs in AC phase-control circuits, specifically used in motor speed controllers and lighting dimmers.
For engineers reviewing the DB3 datasheet, DB3 pinout, DB3 application, or DB3 equivalent, this page delivers verified electrical characteristics, SOT-23-3L and DO-35 package details, real-world timing behavior under capacitive triggering, and validated alternatives for triac-based AC control designs.
Technical Context
The DB3 operates as a symmetrical two-terminal semiconductor switch that conducts only after voltage across its terminals exceeds the breakover threshold in either polarity. Its bidirectional conduction, sub-3 V VBO symmetry, and <2 µs rise time enable precise zero-crossing–independent triggering of main switching devices.
It requires no external bias and functions without gate drive-relying solely on capacitor-charged voltage ramp to reach VBO. The device sustains repetitive peak on-state current up to 2.0 A at 120 Hz with junction temperature maintained between –40 °C and +125 °C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBO Range | 28–36 V - defines minimum AC voltage required to fire connected triac/SCR |
| VBO Symmetry | ≤3 V - ensures matched turn-on thresholds in both polarities for balanced AC phase control |
| IBO Max | 50 µA - low trigger current enables use with high-impedance RC timing networks |
| tr Max | 2 µs - fast transition supports clean gate pulse generation without ringing or false triggering |
| ITRM | 2.0 A - maximum repetitive surge current handling capability at 120 Hz line frequency |
| Tj Range | –40 to +125 °C - operational thermal envelope suitable for enclosed industrial and lighting environments |
| IR Max | 10 µA at 0.5×VBO - minimal leakage preserves RC timing accuracy over temperature and life |
Pinout & Package
SOT-23-3L and DO-35 packages are offered for DB3. Pin 1 and Pin 3 must be shorted together per functional requirement; the device operates as a two-terminal component despite three physical leads in SOT-23-3L.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 | Anode / Main Terminal 1 (MT1) | One conduction path terminal; electrically tied to Pin 3 in application layout |
| Pin 2 | Center Terminal / No Internal Connection | Thermal pad / mechanical support only; not bonded to die |
| Pin 3 | Cathode / Main Terminal 2 (MT2) | Second conduction path terminal; shorted to Pin 1 to form functional DIAC node |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Breakover | Identical 28–36 V threshold in both polarities enables single-component AC phase control |
| VBO Symmetry ≤3 V | Ensures consistent firing angle across positive/negative half-cycles for reduced harmonic distortion |
| Low IBO (50 µA max) | Permits use with MΩ-range resistors and nF-range capacitors in compact timing networks |
| ECOPACK®2 Compliance | Meets RoHS and halogen-free requirements for industrial and consumer lighting applications |
| Robust Thermal Rating | –40 to +125 °C operation supports deployment in thermally constrained ballast and dimmer enclosures |
Applications
| Motor Speed Control | LED Lamp Ballast Start-up |
|---|---|
Use Scenario: Variable-speed fan or pump driven by phase-controlled AC supply using triac output stage. IC Role / Device Role / Timing Role: DIAC trigger element initiating triac conduction at adjustable phase angle determined by RC network. Use Value: Enables smooth, low-noise speed regulation without microcontroller or zero-cross detection circuitry. | Use Scenario: Cold-start ignition of LED driver ICs requiring initial high-voltage pulse to activate bootstrap circuitry. IC Role / Device Role / Timing Role: Voltage-triggered switch delivering controlled gate pulse to start resonant converter controller. Use Value: Eliminates need for dedicated HV startup IC while maintaining reliable cold-start performance down to –25 °C. |
| Fluorescent Tube (TL) Ballast | AC Light Dimmer |
Use Scenario: Electronic ballast for T8/T5 fluorescent lamps requiring preheat and ignition sequence. IC Role / Device Role / Timing Role: Initiates thyristor-based preheat timer and subsequent lamp strike pulse generator. Use Value: Provides repeatable, temperature-stable ignition timing across 10,000+ lamp cycles. | Use Scenario: Wall-mounted leading-edge dimmer controlling mains-powered incandescent or halogen lamps. IC Role / Device Role / Timing Role: Sets conduction angle of main triac via RC-delayed breakover event synchronized to AC waveform. Use Value: Delivers flicker-free dimming with <±1.5° phase jitter across 90–264 VAC input range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DIAC trigger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMDB3 | VBO range 28–36 V (same), but rated ITRM = 1.0 A vs. 2.0 A; SOT-23-3L only | Lower surge current rating limits use in high-power triac drivers (>500 W) | Select when board space is critical and peak load current remains ≤1 A |
| DB4 | VBO range 35–45 V (higher), same IBO (50 µA), identical package options | Requires larger RC timing components to achieve same phase angle; better for 230 VAC systems | Select for 230 VAC mains applications where higher VBO improves noise immunity and reduces false triggering |
Compared with SMDB3 and DB4, DB3 offers the optimal balance of robust 2 A surge handling, 28–36 V VBO for universal 100–240 VAC compatibility, and dual-package availability-making it the default choice for cost-sensitive, high-volume AC control modules.
Availability
DB3 is available at Aetrix Electronics and suitable for motor speed controllers, LED lighting ballasts, fluorescent lamp igniters, and AC light dimmers requiring stable component supply across multi-year production cycles.
Supply support for DB3 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, Switzerland, designing and manufacturing analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.
DB3 belongs to ST's discrete power portfolio, engineered specifically for reliable, low-cost AC phase control and lamp ignition-emphasizing thermal resilience, parameter consistency, and long-term stability in harsh electromagnetic environments.
FAQ
What is the correct way to connect DB3 in a triac gate triggering circuit?
DB3 must be connected between the triac gate and MT1, with its two functional terminals (Pin 1 and Pin 3, shorted externally) forming the DIAC node. A series resistor and parallel capacitor (e.g., 100 kΩ + 100 nF) set the phase delay; DB3 fires when capacitor voltage reaches VBO, delivering a sharp current pulse to the triac gate.
Can DB3 replace DB4 in an existing design?
Direct replacement is possible only if the circuit's RC timing network is recalculated to maintain the same firing angle-since DB4's higher VBO (35–45 V) delays conduction relative to DB3 (28–36 V). Failure to adjust may cause reduced output power or unstable dimming at low settings.
Does DB3 require heatsinking in typical dimmer applications?
No. DB3 dissipates negligible power (<10 mW average) during normal operation because it conducts only briefly per half-cycle. Its SOA is fully covered within the –40 to +125 °C junction temperature range even in sealed plastic enclosures with no airflow.
Is DB3 compliant with lead-free assembly processes?
Yes. DB3 meets JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1) and is qualified for lead-free reflow up to 260 °C peak temperature. Its ECOPACK®2 designation confirms compliance with RoHS Directive 2011/65/EU and halogen-free material requirements.
DB3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diotec Semiconductor
- Series:
- -
- Package/Case:
- DO-204AH, DO-35, Axial
- Packaging:
- Cut Tape (CT)
- Product Status:
- Active
- Voltage - Breakover:
- 28 ~ 36V
- Current - Breakover:
- 200 µA
- Current - Hold (Ih) (Max):
- -
- Current - Peak Output:
- 2 A
- Operating Temperature:
- -50°C ~ 100°C (TJ)
- Supplier Device Package:
- DO-35
DB3 FAQ
1.How can I place an order for DB3 through Aetrix?
Please submit a Request for Quotation (RFQ) for DB3 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 DB3 reliable?
The price and inventory of DB3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DB3 is usually 5 days.
3.What payment methods are accepted for DB3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DB3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DB3?
DB3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DB3 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 DB3?
For technical support, including DB3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DB3 requirements.
6.How does Aetrix verify that DB3 is sourced from the original manufacturer or authorized distributors?
All DB3 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 DB3 meets industry standards.
7.What is the process for return or replacement of DB3?
All DB3 units undergo pre-shipment inspection (PSI). If there is an issue with DB3, 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 DB3 part is unused and in its original packaging.
Return procedure for DB3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
DB3 Tags
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