Diodes Incorporated SD1A180E

Overview

SD1A180E from Littelfuse (formerly acquired KEC/KDX) is a unidirectional SIDAC thyristor designed for controlled high-voltage trigger applications, featuring a nominal breakover voltage of 180 Vdc (range 170–190 V), 1 A RMS on-state current, and 150 V repetitive blocking voltage (V_DRM). It operates across –40°C to +125°C junction temperature and is used in gas igniter circuits where precise, self-triggering voltage threshold and low holding current (<60 mA) are critical.

For engineers reviewing the SD1A180E datasheet, SD1A180E pinout, SD1A180E application, or SD1A180E equivalent, key selection criteria include verified V_BO tolerance (±10 V), di/dt capability (≥80 A/μs), thermal resistance (R_thJC = 15 °C/W), DO-41 package compatibility, and compliance with RoHS 2011/65/EU for ignition system integration.

Technical Context

The SD1A180E is a two-terminal, unidirectional, negative-resistance switching device that conducts only after forward voltage exceeds its temperature-dependent breakover threshold (V_BO = 170–190 V). It latches on until current falls below the holding current (I_H ≤ 60 mA) and exhibits no gate control-unlike SCRs-making it suitable for simple, passive overvoltage-triggered discharge paths.

Its 80 A/μs critical rate of rise of on-state current (di/dt) ensures reliable turn-on without false triggering under fast-rising transients, while the 15 °C/W junction-to-case thermal resistance supports sustained 1 A RMS conduction at TL = 80°C in DO-41 packages with adequate PCB copper area.

Key Specifications

Pinout & Package

Package: JEDEC DO-41 molded plastic case with lead-free plating; axial leads, RoHS-compliant, rated for 260°C soldering (10 s, lead length ≥1/16″).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar unidirectional SIDAC trigger applications.

Compared with SD1A180 and KSC180E, the SD1A180E provides guaranteed RoHS compliance and updated lifecycle support while maintaining identical electrical behavior and board-level interchangeability-making it the preferred choice for new designs targeting global regulatory alignment and supply chain continuity.

Availability

SD1A180E is available at Aetrix Electronics and suitable for gas igniters, appliance pilot light circuits, and industrial burner controls requiring stable component supply, consistent V_BO distribution, and RoHS-compliant manufacturing.

Supply support for SD1A180E 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, with expertise in thyristors, SIDACs, and ignition semiconductors for safety-critical systems.

The SD1A180E belongs to Littelfuse's legacy KDXD SIDAC product line, engineered specifically for high-reliability, low-maintenance gas ignition in residential and commercial heating appliances.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The SD1A180E has an operating junction temperature range of –40°C to +125°C. For continuous 1 A RMS conduction, thermal design must ensure junction temperature remains ≤125°C, typically requiring a heatsink or sufficient PCB copper area given its 15 °C/W junction-to-case resistance and 1.3 W typical on-state power dissipation.

Can SD1A180E be used in AC line-triggered applications?

Yes-its 150 V V_DRM rating supports use with 120 V RMS AC mains (peak ≈170 V) when paired with appropriate series impedance to limit peak current and ensure V_BO is exceeded only during intended ignition pulses; however, it is not rated for continuous AC line switching.

Is SD1A180E pin-compatible with standard DO-41 diodes?

Yes-SD1A180E uses the JEDEC DO-41 package with axial leads and identical mechanical dimensions (length ≈4.5 mm, diameter ≈2.7 mm), enabling drop-in replacement in existing diode footprints; polarity must be observed (anode/cathode orientation matches standard DO-41 diode marking convention).

Does SD1A180E require a snubber circuit?

A snubber is not required for basic gas igniter operation, but recommended when driving inductive loads or when di/dt exceeds 80 A/μs. The device's inherent 80 A/μs di/dt rating handles typical capacitor-discharge waveforms; however, a small RC snubber (e.g., 100 Ω + 100 pF) improves reliability in noisy EMI environments or with long PCB traces.