Diodes Incorporated SD1A150G

Overview

SD1A150G from Littelfuse is a unidirectional silicon SIDAC (Silicon Diode for Alternating Current) thyristor designed for precise, self-triggering AC/DC switching in high-voltage ignition circuits. It features a nominal breakover voltage of 150 V (range 142–157 V), 1 A RMS on-state current rating, 120 V repetitive peak off-state voltage (VDRM), <60 mA holding current, and DO-15 plastic package compliant with RoHS and UL E219635.

For engineers reviewing the SD1A150G datasheet, SD1A150G pinout, SD1A150G application, or SD1A150G equivalent, key selection criteria include verified breakover voltage tolerance, thermal resistance (15 °C/W junction-to-case), di/dt capability (80 A/µs), low IDRM (<10 µA), and compatibility with gas igniter timing and energy delivery requirements.

Technical Context

The SD1A150G operates as a two-terminal, voltage-triggered bidirectional switch that conducts only after forward voltage exceeds its temperature-dependent breakover threshold (VBO). Unlike SCRs or TRIACs, it requires no gate control - conduction initiates solely when applied voltage crosses VBO, then sustains until current falls below IH.

Its internal structure enables fast turn-on (di/dt ≥80 A/µs), low on-state voltage drop (1.1–1.5 V at 1 A), and stable performance across –40°C to +125°C junction temperature. The device exhibits predictable VBO drift (±12% over temperature) and minimal leakage (IDRM ≤10 µA at 120 V).

Key Specifications

Pinout & Package

DO-15 molded plastic package with axial leads; RoHS-compliant lead-free plating; UL Recognized (File #E219635); case meets JEDEC DO-15 mechanical standard.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar unidirectional voltage-triggered switching applications.

Compared with SD1A120G and SD1A200G, the SD1A150G provides optimal balance between reliable triggering at 120 VAC-derived voltages and sufficient margin against line surges - critical for residential gas appliance certification and long-term reliability.

Availability

SD1A150G is available at Aetrix Electronics and suitable for gas igniters, appliance safety interlocks, capacitor discharge ignition modules, and industrial flame detection feedback requiring stable component supply and UL-recognized reliability.

Supply support for SD1A150G 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

Littelfuse is a global manufacturer of circuit protection, power control, and sensing technologies, founded in 1927 and headquartered in Chicago, Illinois.

The SD1A series belongs to Littelfuse's SIDAC product line, engineered specifically for contactless, voltage-triggered switching in high-reliability ignition and safety-critical AC/DC control applications.

FAQ

What is the maximum junction temperature for SD1A150G?

The SD1A150G has a specified operating junction temperature range of –40°C to +125°C. This rating is validated per JEDEC test conditions and supports continuous operation in enclosed appliance environments where ambient temperatures may exceed 85°C, provided thermal resistance (R_thJC = 15 °C/W) and PCB copper area are properly managed.

Can SD1A150G replace a TRIAC in an AC switching application?

No - SD1A150G is a unidirectional, two-terminal SIDAC with no gate control and no reverse conduction capability. It cannot commutate AC waveforms like a TRIAC. It is intended only for voltage-triggered, single-polarity pulse generation - such as in gas igniter primary-side switching - not full-wave AC phase control.

Is SD1A150G RoHS and UL compliant?

Yes - the SD1A150G meets RoHS Directive 2011/65/EU requirements with lead-free plating and carries UL Recognition under File #E219635. Its DO-15 package is certified for flammability (UL 94 V-0) and electrical insulation per UL standards applicable to discrete semiconductor devices.

How does temperature affect the breakover voltage (V_BO) of SD1A150G?

V_BO decreases linearly with increasing junction temperature, exhibiting approximately –0.1%/°C drift. At 125°C, V_BO is ~88% of its 25°C value (e.g., 150 V → ~132 V), as confirmed by Fig.3 in the datasheet. Designers must account for this shift when setting RC timing networks for consistent ignition timing across operating temperature ranges.