40 A snubberless alternistor — the inductive-load workhorse that went obsolete
The STMicroelectronics TPDV640RG is a single alternistor triac rated for 40 A RMS on-state current and 600 V off-state voltage, in a TOP-3 through-hole package. It is classified as an Alternistor – Snubberless type, meaning it is designed to commutate inductive loads — motors, solenoids, transformers — without the external RC snubber network that standard triacs require. That snubberless construction is the main design-in advantage: it saves two or three passive components per channel and eliminates the layout headache of routing the snubber loop close to the triac.
The 40 A RMS rating sets the continuous load ceiling — a resistive heater drawing 30 A at 240 VAC is comfortably inside the SOA, but a motor with a 50 A inrush requires the surge capability: the TPDV640RG is rated for 350 A at 50 Hz and 370 A at 60 Hz non-repetitive surge. The 200 mA gate trigger current is on the high side; it demands a gate driver capable of sourcing that peak, so a standard logic-level output from an MCU or optocoupler will need a transistor buffer. The 1.5 V gate trigger threshold is compatible with a 5 V or 12 V drive rail. The 50 mA holding current means the triac will latch on with a minimum load of about 12 W at 240 VAC — below that, the device may drop out at zero-cross, which matters for low-power loads like small fans. The TOP-3 package is a through-hole power package with a large metal tab for heatsinking. The tab is electrically live (typically MT2), so the heatsink must be isolated or the mounting hole must use a shoulder washer and insulating pad.
The TPDV640RG is marked obsolete.