SMDB3

Overview

The SMDB3 is a surface mount bidirectional trigger diode (DIAC) manufactured by STMicroelectronics. It functions as a trigger device with fixed voltage references, designed for use in conjunction with triacs to simplify gate control circuits or as a starting element in fluorescent lamp ballasts. The component utilizes an SOT23-3L package, enabling compact designs suitable for automated manufacturing processes. Key electrical characteristics include breakover voltages of 32 V and 40 V, a low breakover current, and a breakover voltage symmetry of 3V.

Feature Summary

• Surface mount SOT23-3L package facilitates compact design and automated manufacturing integration
• Functions as a trigger diode with fixed voltage reference for simplified gate control
• Low breakover current specification enhances sensitivity in triggering applications

Applications

• Gate control circuits utilizing triacs
• Starting elements in fluorescent lamp ballasts
• AC switching applications requiring symmetrical triggering

Procurement Notes

Verify the current production status of the SMDB3 before finalizing designs, as it is listed as obsolete in available records. Confirm availability through authorized distributors or check for valid replacement components within the DB3/DB4 series that maintain equivalent electrical specifications and package compatibility for existing inventory management.

Selection Notes

Select the SMDB3 when a surface mount DIAC is required for space-constrained PCB layouts. Ensure the application demands the specific 32 V or 40 V breakover voltage options provided by this series. Verify that the SOT23-3L footprint aligns with the board design constraints and that the low breakover current meets the sensitivity requirements of the associated triac gate circuit.

Part Context

The SMDB3 belongs to the DB3/DB4 family of DIACs produced by STMicroelectronics. This series is engineered to provide reliable triggering for thyristor-based AC power control systems. The transition from through-hole DO-35 packages to the surface mount SOT23-3L format allows for modernization of legacy designs while maintaining the core functionality of symmetrical breakdown voltage characteristics essential for phase control applications.

Replacement Considerations

Consult the official STMicroelectronics documentation for confirmed substitute part numbers if the SMDB3 is unavailable. Potential alternatives may include other DIACs in the SOT23-3L package with matching 32 V or 40 V breakover voltages and similar symmetry specifications.