Littelfuse has introduced an optically isolated photovoltaic gate driver for mosfets and IGBTs.

Essentially, photovoltaic gate drivers are opto-isolated relays without the internal output mosfets, allowing mosfets to be picked appropriate to the load.

They are not fast, but they allow a microcontroller to switch a large load on and off across a huge potential difference.

This one is called FDA117, and its input to output isolation is 5kVrms (6kVrms at 50 or 60Hz for 1s).

It will generate ~13.3V with a 5mA drive (25°C), or drive ~9μA into a short-circuit (2.5μA min).

While the open-circuit voltage does not rise much, the output current increases with higher input current to speed gate charging.

This increase is roughly proportional: 19μA at 10mA, 39μA at 20mA and 60μA at 30mA. Above 30mA there is less gain, with ~73mA available at the abs max drive of 50mA. LED forward voltage is ~1.36V at 5mA.

Output current falls off with increasing temperature. With drives up to 15mA, output is fairly stable to 80°C, but for 30mA it starts to drop at 25°C. Output voltage is also temperature dependent – at -40°C it is ~17V, dropping to 10V at 100°C.

When input current is removed, the output presents a ~900Ω (100Ω min, 3.3kΩ max) load to drain the gate of charge and turn off the mosfet or IGBT.

Typical transition times between 500mV and 5V, with 5mA input and a 200pF gate, are 160ns rising and 190ns falling. Increasing input to 10mA speeds the rising edge to 75ns, while fall time is almost unaltered at 200ns.

Packaging is 4pin DIP through-hole or a surface-mount package based on a 4pin DIP.

The part is UL certified, and EN62368-1 certification is pending.

The company sees its isolated gate driver being used in industrial, energy, building automation and smart homes.