Diodes Incorporated SD1A240G

Overview

SD1A240G from Littelfuse (formerly acquired LSC) is a unidirectional silicon thyristor (SIDAC) designed for high-voltage, low-current triggering in gas igniter circuits. It features a 240 V nominal breakover voltage (VBO = 230–250 V), 210 V peak repetitive off-state voltage (VDRM), 1 A RMS on-state current rating, and ≤60 mA holding current (IH), enabling reliable ignition pulse generation in compact appliance designs.

For engineers reviewing the SD1A240G datasheet, SD1A240G pinout, SD1A240G application, or SD1A240G equivalent, key selection criteria include verified VBO tolerance, di/dt capability (≥220 A/μs), thermal resistance (RthJC = 15 °C/W), RoHS-compliant DO-15 packaging, and UL Recognition File #E219635 compliance for safety-critical ignition systems.

Technical Context

The SD1A240G operates as a two-terminal, voltage-triggered switching device with no gate control - conduction initiates when applied voltage exceeds its temperature-dependent breakover threshold (VBO). Its unidirectional structure supports AC half-cycle triggering only, requiring external timing or phase-control circuitry for precise ignition timing.

It exhibits a typical on-state voltage of 1.1–1.5 V at 1 A, critical for minimizing power loss during brief high-current pulses, and maintains stable VBO over –40°C to +125°C junction temperature, with <±10% drift across operating range per Fig.3.

Key Specifications

Pinout & Package

Package: JEDEC DO-15 molded plastic case with lead-free plating, RoHS 2011/65/EU compliant, UL Recognized (File #E219635). Dimensions: A = 25.4 mm max, B = 0.71–0.86 mm, C = 2.60–3.60 mm, D = 5.80–7.60 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SIDAC-based ignition applications.

Compared with SD1A240G, TS1220-8 offers tighter IH but sacrifices 10 V VDRM margin, while S1220S trades di/dt headroom for broader distributor availability - both require revalidation of spark energy and thermal rise in existing PCB layouts.

Availability

SD1A240G is available at Aetrix Electronics and suitable for gas igniters, furnace pilot controls, tankless water heater spark modules, and commercial oven safety interlocks requiring stable component supply and UL-recognized reliability.

Supply support for SD1A240G 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, Inc. is a global manufacturer of circuit protection, power control, and sensing technologies, headquartered in Chicago, Illinois.

The SD1A240G belongs to Littelfuse's legacy SIDAC product line, engineered specifically for robust, maintenance-free AC-triggered spark generation in gas-fired heating and cooking equipment.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The SD1A240G has an operating junction temperature range of –40°C to +125°C. Continuous operation at the upper limit requires adherence to the derating curve in Fig.2: at TL = 80°C, IT(RMS) is rated at 1 A; above this case temperature, RMS current must be linearly reduced to maintain TJ ≤ 125°C, considering RthJC = 15 °C/W and ambient thermal conditions.

Can SD1A240G be used in bidirectional AC applications without external components?

No. The SD1A240G is a unidirectional thyristor and conducts only during positive half-cycles of AC voltage. For full-wave triggering, two devices in inverse-parallel configuration or a dedicated bidirectional SIDAC (e.g., K2200S) are required - using a single SD1A240G in reverse polarity will not block or trigger correctly and may suffer permanent damage.

Is lead-free soldering compatible with the SD1A240G package?

Yes. The SD1A240G uses lead-free terminal plating and is qualified for lead-free reflow soldering per J-STD-020. Maximum lead solder temperature is specified at 260°C for 10 seconds with lead length ≥1/16 inch from case. Reflow profiles must avoid exceeding this thermal limit to prevent internal bond wire degradation or mold compound delamination.

How does junction temperature affect breakover voltage performance?

VBO decreases linearly with rising junction temperature, as shown in Fig.3: VBO(TJ)/VBO(25°C) drops to ~0.9× nominal at +125°C. At –40°C, VBO rises to ~1.1× nominal. Designers must account for this ±10% variation across the full –40°C to +125°C range when setting transformer turns ratio and spark gap clearance to ensure reliable ignition under all thermal conditions.