Compared to traditional electromechanical relays, says IR, the PVN012A family offers a smaller footprint, high input-to-output isolation, bounce-free operation, solid-state reliability, stable on-resistance over life, and greater input sensitivity.

The new 20V, single-pole, normally open, solid-state relays use a HEXFET MOSFET output switch, driven by an integrated photovoltaic generator circuit. The output switch is controlled by radiation from a GaAlAs LED that's optically isolated from the photovoltaic generator. The new series is available in a 6-pin DIP, 6-pin SMT, and tape-and-reel.

MOSFET driver IC
In another development, Allegro MicroSystems Europe's dual, full-bridge, gate-driver IC with integrated microstepping translator circuitry drives a range of industrial bipolar two-phase stepper motors in the 30-500 W power range (Fig. 2). Motor power is provided by external N-channel power MOSFETs at supply voltages from 12 to 50 V.

The A3986 contains two sinusoidal digital/analogue converters that generate the reference voltage for two separate, fixed, off-time, pulse-width-modulated current controllers. These provide current regulation for external power-MOSFET, full-bridge circuits. Motor stepping is controlled by the two-wire step and direction interface, providing complete microstepping control at full-, half-, quarter- and sixteenth-step resolutions.

The fixed off-time regulator can operate in slow-, mixed- or fast-decay modes, which results in reduced audible motor noise, increased step accuracy, and reduced power dissipation.

The translator is the key behind the driver IC's easy implementation. Simply inputting one pulse on the "step" input drives the motor one step (full, half, quarter, or 16th depending on the microstep select input). There are no phase-sequence tables, high-frequency control lines, or complex interfaces to program.

The above-supply voltage required for the high-side N-channel MOSFETs is provided by a bootstrap capacitor. Efficiency is enhanced via synchronous rectification, and the power FETs are protected from shoot-through by integrated crossover control and programmable dead time. In addition to crossover current control, internal circuit protection provides thermal shutdown with hysteresis and undervoltage lockout.