Diodes Incorporated SD1A180G

Overview

SD1A180G from Littelfuse (formerly acquired from KEC/LSC) is a unidirectional SIDAC thyristor designed for high-voltage, low-current trigger applications in gas igniters and pulse generators. It features a nominal breakover voltage of 180 Vdc (range 170–190 V), 1 A RMS on-state current rating, 150 V peak repetitive off-state voltage (VDRM), and holding current ≤60 mA at 25°C.

For engineers reviewing the SD1A180G datasheet, SD1A180G pinout, SD1A180G application, or SD1A180G equivalent, key selection criteria include verified VBO tolerance, di/dt capability ≥80 A/μs, thermal resistance (RthJC = 15 °C/W), RoHS-compliant DO-15 packaging, and UL recognition (File #E219635).

Technical Context

The SD1A180G 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 forward-triggered, self-latching behavior once triggered, sustaining conduction until current falls below IH.

It exhibits a typical on-state voltage of 1.1–1.5 V at 1 A, critical rate of rise of on-state current (di/dt) ≥80 A/μs, and junction-to-case thermal resistance of 15 °C/W-enabling reliable pulsed operation in compact, thermally constrained igniter modules.

Key Specifications

Pinout & Package

Package: JEDEC DO-15 molded plastic case with lead-free plating; RoHS-compliant (2011/65/EU); 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 unidirectional SIDAC trigger applications.

Compared with KIA180G and BT169D, SD1A180G uniquely combines UL recognition, self-triggering operation, and tight VBO tolerance-making it the only drop-in solution for certified gas igniter designs requiring zero external trigger components.

Availability

SD1A180G is available at Aetrix Electronics and suitable for gas igniters, electronic lighters, appliance pilot systems, and industrial burner controls requiring stable component supply and long-term lifecycle continuity.

Supply support for SD1A180G 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 leader in circuit protection, power control, and sensing technologies, with deep expertise in thyristors and overvoltage protection devices.

The SD1A180G belongs to Littelfuse's legacy SIDAC portfolio-engineered specifically for robust, maintenance-free ignition in residential and commercial gas appliances.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The SD1A180G has an operating junction temperature range of –40°C to +125°C. For continuous RMS current operation at 1 A, the case temperature must be maintained at ≤80°C per the IT(RMS) derating curve. Exceeding TJ = 125°C risks irreversible degradation of the silicon junction and premature failure.

Can SD1A180G be used in AC line-powered circuits without isolation?

No-SD1A180G is not rated for direct connection to mains AC without galvanic isolation. Its VDRM of 150 V limits use to circuits with peak voltages ≤150 V. In 120 Vrms AC applications, peak voltage reaches ~170 V, exceeding VDRM; therefore, it must be used behind a step-down transformer or with series impedance limiting peak stress.

Is SD1A180G compatible with lead-free reflow soldering processes?

Yes-the device uses lead-free terminal plating and is qualified for standard Pb-free reflow profiles. Maximum lead solder temperature is specified at 260°C for 10 seconds, with lead length ≥1/16 inch from the case. Reflow profiles must avoid thermal shock and maintain time-above-liquidus within JEDEC J-STD-020 limits.

Does SD1A180G require a snubber network in typical igniter applications?

A snubber is not required for basic resistive or transformer-coupled igniter loads due to its 80 A/μs di/dt rating and inherent voltage clamping behavior. However, in inductive load configurations (e.g., direct coil drive), a small RC snubber (e.g., 100 Ω + 100 pF) is recommended to suppress voltage overshoot during current interruption and prevent false re-triggering.