Diodes Incorporated SD1A120GW

Overview

SD1A120GW from Littelfuse is a unidirectional silicon thyristor (SIDAC) designed for high-voltage pulse triggering in ignition circuits, with confirmed V_BO = 105–120 V, V_DRM = 90 V, I_H ≤ 60 mA, I_T(RMS) = 1 A, and DO-15 package. It operates across –40°C to +125°C and is used in gas and HID lamp igniters where precise breakover voltage control and compact high-voltage switching are required.

For engineers reviewing the SD1A120GW datasheet, SD1A120GW pinout, SD1A120GW application, or SD1A120GW equivalent, key selection criteria include verified breakover voltage tolerance, holding current stability over temperature, RMS current derating at elevated lead temperature, and RoHS-compliant DO-15 mechanical compatibility with automated through-hole assembly.

Technical Context

This SIDAC functions as a voltage-triggered bidirectional switch without gate control-conducting only after forward voltage exceeds V_BO, then latching until current falls below I_H. Its unidirectional conduction path and absence of gate terminal distinguish it from SCRs and TRIACs.

It exhibits a typical thermal resistance R_thJC of 15°C/W and supports repetitive 5 Hz pulsed operation up to 80 A peak (10 µs), with di/dt capability ≥80 A/µs-critical for fast-rising ignition pulses in high-intensity discharge systems.

Key Specifications

Pinout & Package

DO-15 molded plastic package with axial leads; RoHS-compliant lead-free plating; case conforms to JEDEC standard 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 thyristor pulse triggering applications.

Compared with SD1A120G and K2203E, SD1A120GW offers the narrowest V_BO range (105–120 V) and lowest I_H, making it optimal for timing-critical, low-power igniter and flame-sensing circuits where repeatable conduction onset and secure latching are mandatory.

Availability

SD1A120GW is available at Aetrix Electronics and suitable for gas igniters, HID lamp starters, and industrial pulse generators requiring stable component supply with guaranteed long-term manufacturability and RoHS compliance.

Supply support for SD1A120GW 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, headquartered in Chicago, Illinois, with design and manufacturing operations across Asia, Europe, and the Americas.

SD1A120GW belongs to Littelfuse's SIDAC family-engineered specifically for high-reliability, high-voltage pulse switching in ignition, lighting, and industrial timing applications where gateless voltage-triggered behavior is essential.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The SD1A120GW has a rated operating junction temperature range of –40°C to +125°C. Continuous operation at +125°C is permitted only when I_T(RMS) is derated to ≤0.65 A per thermal curves in the datasheet, and ambient conditions maintain case temperature ≤80°C. Exceeding these limits accelerates parameter drift and reduces lifetime.

Can SD1A120GW replace an SCR in a gate-controlled circuit?

No-SD1A120GW is a gateless, voltage-triggered SIDAC with no gate terminal. It cannot be turned on or off by external control signals like an SCR. Substitution requires redesigning the trigger circuit to rely solely on voltage threshold crossing, not gate drive timing or logic-level control.

Is lead-free soldering compatible with the DO-15 package?

Yes-the SD1A120GW uses lead-free plating on axial leads and is qualified for lead-free reflow and wave soldering. Maximum lead solder temperature is 260°C for ≤10 seconds at ≥1/16″ from case body, per JEDEC J-STD-020 and RoHS 2011/65/EU requirements.

How does junction temperature affect breakover voltage?

Per Figure 3 in the datasheet, V_BO decreases linearly with rising junction temperature: V_BO(T_J) ≈ V_BO(25°C) × [1 – 0.0012 × (T_J – 25)]. At +125°C, V_BO drops ~12%, shifting from 120 V to ~106 V-critical for timing-critical igniter designs operating at elevated ambient temperatures.