Cutting-Edge Gate Voltage Generator Empowers MOSFETs and IGBTs with Opto-Isolation

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

Photovoltaic gate drivers, essentially opto-isolated relays without the internal output mosfets, allow mosfets to be chosen appropriately for the load.

While they may not be fast, they enable a microcontroller to switch a large load on and off across a significant potential difference.

The newly introduced FDA117 offers an input to output isolation of 5kVrms (6kVrms at 50 or 60Hz for 1s).

With a 5mA drive at 25°C, it generates approximately 13.3V or drives around 9μA into a short-circuit (2.5μA min).

Although the open-circuit voltage does not increase significantly, the output current rises with higher input current to speed gate charging.

This increase is roughly proportional, with 19μA at 10mA, 39μA at 20mA, and 60μA at 30mA. Beyond 30mA, the gain decreases, with approximately 73mA available at the absolute maximum drive of 50mA. The LED forward voltage is approximately 1.36V at 5mA.

Output current decreases with increasing temperature. For drives up to 15mA, the output remains fairly stable up to 80°C. However, for 30mA, it starts to decline at 25°C. The output voltage is also temperature dependent, with approximately 17V at -40°C, dropping to 10V at 100°C.

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

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

The packaging options include a 4-pin DIP through-hole or a surface-mount package based on a 4-pin DIP.

The FDA117 is UL certified, and EN62368-1 certification is pending.

Littelfuse envisions its isolated gate driver being utilized in various industries such as industrial, energy, building automation, and smart homes.

The FDA117 product page can be found here.