Diodes Incorporated SD1A220A

Overview

SD1A220A from Littelfuse is a unidirectional SIDAC (Silicon Diode for Alternating Current) thyristor designed for high-voltage, low-current trigger applications. It features a 220 V breakover voltage (V_BO = 210–226 V), 190 V peak repetitive blocking voltage (V_DRM), 1 A RMS on-state current rating, <60 mA holding current (I_H), and DO-214AC (SMA) surface-mount package - used primarily in gas igniter circuits requiring precise, self-triggering voltage threshold behavior.

For engineers reviewing the SD1A220A datasheet, SD1A220A pinout, SD1A220A application, or SD1A220A equivalent, key selection criteria include verified V_BO tolerance (±3 V), thermal resistance (R_thJC = 15 °C/W), di/dt capability (≥80 A/μs), junction temperature range (–40 to +125 °C), and RoHS-compliant lead-free termination per UL File E219635.

Technical Context

The SD1A220A operates as a two-terminal, negative-resistance switching device that triggers into conduction when applied voltage exceeds its temperature-dependent breakover threshold (V_BO). It exhibits no gate control and relies solely on intrinsic semiconductor physics - with V_BO varying ±10% across –40°C to +125°C and I_H decreasing with rising temperature.

Its 15 °C/W junction-to-case thermal resistance supports stable operation at 1 A RMS under TL = 80°C mounting conditions, while its 80 A/μs critical di/dt rating ensures reliable turn-on without false triggering during fast-rising transients in inductive igniter loads.

Key Specifications

Pinout & Package

Package: JEDEC DO-214AC (SMA), molded plastic case with lead-free plating; RoHS-compliant per 2011/65/EU; UL Recognized (File #E219635).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SD1A220A, SD1A220 lacks regulatory compliance for new designs, while K2200H trades compactness and precise V_BO for higher surge tolerance and thermal mass - making SD1A220A optimal for space-constrained, certified gas appliance PCBs requiring repeatable 220 V triggering.

Availability

SD1A220A is available at Aetrix Electronics and suitable for gas igniters, appliance flame detection circuits, industrial burner control systems, and commercial kitchen igniters requiring stable component supply with full traceability and lifecycle management.

Supply support for SD1A220A 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 SD1A220A belongs to Littelfuse's SIDAC family, engineered specifically for reliable, maintenance-free high-voltage triggering in gas-fired heating and cooking equipment.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The SD1A220A has a rated operating junction temperature range of –40°C to +125°C. Continuous operation at +125°C is permitted only when the RMS on-state current remains ≤1 A and thermal resistance to ambient (via PCB copper) maintains junction temperature within this limit - verified per Fig.2 power dissipation curves and R_thJC = 15 °C/W specification.

Can SD1A220A be used in AC line-switching applications?

No - SD1A220A is a unidirectional device rated for DC or half-wave AC triggering only. Its V_DRM of 190 V applies to repetitive forward blocking; it does not support reverse voltage blocking or full-wave AC phase control. For bidirectional AC switching, discrete TRIACs or DIACs like DB3 must be used instead.

How does junction temperature affect breakover voltage?

V_BO decreases linearly with increasing junction temperature: Fig.3 shows V_BO(T_J)/V_BO(25°C) ratio drops to ~0.9 at +125°C, meaning actual V_BO falls to approximately 198–203 V. Designers must account for this drift when setting minimum supply voltage margins for reliable triggering across the full –40°C to +125°C range.

Is the SD1A220A compatible with reflow soldering processes?

Yes - the DO-214AC (SMA) package is qualified for lead-free reflow per J-STD-020. Peak solder temperature must not exceed 260°C for ≤10 seconds, with preheat ramp rates and time-above-liquidus aligned to IPC Class 3 profiles. Avoid thermal shock by limiting cooling rates post-reflow to prevent package cracking.