New Industry Products

High-Voltage / Low-Resistance PTC Thermistors for Pre-Charge Circuits

November 20, 2018 by Paul Shepard

Ametherm has introduced a new series of ceramic PTC circuit protection thermistors that claim the industry’s highest voltage rating with lowest available resistance. The CL20 Series PTC Thermistors provide an alternative to fixed resistors and are optimized for inrush current limiting in pre-charge circuits, degaussing circuits, heater applications, in addition to over-current protection.

The PTC thermistors released today deliver voltage ratings up to 1200Vdc and maximum energy ratings to 600J. The devices offer five resistance values at 25°C from 7.0W to 100.0W — with tolerance down to 25% — to accommodate a variety of pre-charge times. These resistance values remain unchanged over the operating temperature range of -40°C to +110°C.

The CL20 Series of PTC thermistors provides stability and reliability in high-voltage applications, and can withstand hundreds of hits of maximum inrush current without degrading. PTC thermistors do not require reset time and therefore will not result in large inrush current during repetitive use, as their resistance remains in a high state.

Devices in the CL20 Series of PTC thermistors feature a dissipation constant of 22.5mW/°C, heat capacity from 2.0J/°C to 3.45J/°C, transition temperature of +120°C and a thermal time constant of 65 sec. Switch and continuous currents for these PTC thermistors range from 450mA to 1750mA and 225mA to 850mA respectively.

The radial-leaded CL20 Series offers easy PCB mounting, have a diameter of 22mm, straight leads, and most come with optional outside or inside kinked leads.

The CL20 Series of PTC thermistors are available direct or through distributors such as Digi-Key and Mouser. Samples and production quantities are available now, with factory lead times of 10 weeks. Volume pricing for US delivery starts at $1.14 per piece in 1,000-piece quantities.