New PTC Thermistors by Ametherm Offer Industry’s Highest Voltage Rating and Lowest Resistance for Pre-Charge Circuits

CARSON CITY, Nev., Nov. 15, 2018 (GLOBE NEWSWIRE) — Ametherm introduced today a new series of ceramic PTC circuit protection thermistors that combine 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 1200 VDC and maximum energy ratings to 600 J. The devices offer five resistance values at 25 °C from 7.0 W to 100.0 W — 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 22.5 mW/°C, heat capacity from 2.0 J/°C to 3.45J/°C, transition temperature of +120 °C and a thermal time constant of 65 s. Switch and continuous currents for these PTC thermistors range from 450 mA to 1750 mA and 225 mA to 850 mA respectively.

The radial-leaded CL20 Series offers easy PCB mounting, have a diameter of 22 mm, straight leads, and most come with optional outside or inside kinked leads. Ametherm also offers smaller PTC circuit protection devices with diameters from 6 mm to 20 mm.

Device Specification Table:

Ametherm Part # CL20 7R0120 CL20 100120 CL20 200120 MCL20 500100 CL20 101130
Resistance @ 25 °C 7.0 W  ±25% 10.0 W  ±25% 20.0 W  ±25% 50.0 Ω ±25% 100.0 W  ±25%
Transition temp. 120 °C 120 °C 120 °C 120 °C 120 °C
Max. voltage 350 Vrms 480 Vrms 680 Vrms 680 Vrms 1200 VDC
Switch current @ 25°C 1.600 A 0.800 A 0.600 A 0.450 A 1.750 A
Cont. current @ 25 °C 0.850 A 0.400 A 0.300 A 0.225 A 0.650 A
Heat capacity 2.0 J/°C 2.0 J/°C 2.25 J/°C 2.4 J/°C 3.45 J/°C
Dissipation constant 22.50 mW/°C 22.50 mW/°C 22.50 mW/°C 22.50 mW/°C 22.50 mW/°C
Thermal time constant 65.0 s 65.0 s 65.0 s 65.0 s 65.0 s
Max. energy 250 J 250 J 500 J 600 J 600 J
Max. body temp. 172 °C 174 °C 172 °C 178°C 180 °C
Diameter 22 mm 22 mm 22 mm 22 mm 22 mm

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.

For more information on Ametherm’s products or to request a sample, visit Or call 800-808-2434 (toll free in the United States) or 775-884-2434 from outside the U.S. and Canada. Follow Ametherm online at

About Ametherm
Ametherm, headquartered in Carson City, Nevada, was founded in 1994 and specializes in thermistors for temperature sensing and inrush current limiting in industrial, automotive, green energy, AMS (avionics, military and space), and many other markets. Ametherm’s devices are some of the highest rated in the industry and are available in customized versions to meet the needs of specific applications. For more information, visit or call 800-808-2434.

Ametherm Contact:
Lori Morton
(775) 884 2434
[email protected]

A photo accompanying this announcement is available at