World's first SMD inrush current limiter

TDK Corporation has developed the J404, the world's first surface-mountable ICL based on PTC (positive temperature coefficient) technology. Designed for DC voltages of up to 500V and AC voltages of up to 350V, the device (order number B59404J0170A062) automatically and intrinsically limits excessive currents in applications such as DC links and charging devices in electromobility.

Due to the compact dimensions of 13.5mm x 10mm x 11mm (L x W x H), users can save up to 70% space and weight on the PCB with this surface-mount design. The components can also be processed fast in automated production lines. As a result, the new component is ideal for many industrial and automotive applications.

The reference temperature at which the device becomes highly resistive is +170C, with a heat capacity of 1J/K and a thermal time constant of 100s. At room temperature, the electrical resistance is 500 Ohm, with a minimum value of 150 Ohm. The ICL can switch off a defect (short circuit) up to 100 times and up to 100,000 cycles when charging and discharging capacitors.

Large capacitors in DC link circuits, encountered in e-mobility inverters or variable-speed drives in industrial applications, act temporarily like a short circuit at the moment they are switched on. This high energy must not damage other components in the system; the same applies in the event of a defect. A PTC thermistor supplies such protection by heating itself due to the high current and becoming highly resistive in an extremely short time, thereby decreasing the current to a safe level.

The main applications for the device include a traction inverter for xEV, charging and discharging DC link capacitors, variable speed drives, and switched-mode power supplies.