Thermistors
Products (3)
B57235S0509M000 - 5Ω NTC Inrush Current Limiter | TDK
The TDK B57235S0509M000 is a leaded NTC thermistor designed for inrush current limiting (ICL) in switch-mode power supplies, with a 25°C reference resistance of 5 Ω ±20%, a 4.2 A steady-state maximum current, and a 9.50 mm diameter coated disk supplied on a 5.00 mm lead spacing. The device belongs to the S 235 family and is also marketed under the legacy EPCOS B57235S0509M000 designation, making it a drop-in for both TDK and former EPCOS part orders. An NTC (Negative Temperature Coefficient) inrush current limiter is a thermistor whose resistance falls as its body temperature rises. At the moment a large bulk capacitor bank or transformer primary is energized, the cold thermistor presents its full 5 Ω to the circuit, charging the capacitors gently and absorbing the worst of the charging spike. As inrush current flows, I²R self-heating drives the resistance down by an order of magnitude or more, leaving the part thermally stable at low ohmic loss during normal steady-state operation. The category sits within thermistors -> passive components -> circuit protection devices, and is one of the simplest and most economical soft-start methods for AC-DC and DC-DC converters. Key features include a wide operating temperature window of -40 °C to +170 °C suitable for commercial and industrial environments, tinned copper leads with a kinked geometry for through-hole mounting, a flame-retardant coating rated 94 V-0, and an ICL max current rating of 4 A continuous (with 4.2 A as the steady-state maximum). The epoxy-coated disk dissipates inrush energy as heat during the first few line cycles and then settles to a low-resistance steady state so that operating losses are minimized. Typical applications include input filtering for switch-mode power supplies, soft-start of large aluminum-electrolytic capacitor banks, protection of rectifier bridges and MOSFETs at turn-on, soft-start of motors and transformers, and as a coarse surge suppressor at the AC mains input. The 5 Ω cold resistance is well matched to 100-240 VAC class supplies charging 100 µF to 1000 µF bulk capacitance banks. When designing with this part, verify that the steady-state RMS current after warm-up remains comfortably below the 4.2 A rating, otherwise the thermistor will not return to its low-R steady state. Place the device on the high-side of the AC line after the fuse so that the fuse clears if the thermistor shorts, and provide at least 10 mm of lead clearance to nearby hot components to avoid derating.
B57236S0100M000V9 - 10Ω NTC Inrush Current Limiter | TDK | SMPS
The TDK B57236S0100M000V9 is an NTC thermistor-based inrush current limiter (ICL) with a nominal cold resistance of 10 Ω ±20% and a maximum permissible inrush current of 3.5 A, supplied through a 0.453" (11.50 mm) lead pitch radial package originally released by EPCOS and now manufactured by TDK. The V9 suffix denotes a specific packaging/lot variant of the B57236S0100M000 base part. It is designed to suppress the high inrush current drawn by large filter capacitors in switch-mode power supplies (SMPS) when AC mains is first applied. An NTC (negative temperature coefficient) thermistor is a passive component whose resistance decreases as its body temperature rises. When a cold thermistor (high resistance) is placed in series with the AC line, it absorbs the initial capacitor-charging surge; once current flows and self-heats the ceramic body, resistance drops to a few hundred milliohms, leaving only a small steady-state power dissipation. NTC inrush limiters thus sit in the passive component family alongside resistors, capacitors and inductors, and serve as a dedicated safety-and-reliability subcategory of power-supply protection. Key features of the B57236S0100M000V9 include a 10 Ω ±20% cold resistance, 3.5 A steady-state current capability, and a 0.453" (11.50 mm) lead spacing that fits industry-standard through-hole ICL footprints. The device carries UL (E338926), CQC, IEC 60539-1-1 (AT0002) and VDE 40038223 safety certifications, making it suitable for worldwide SMPS and industrial electronics deployments. Its leaded radial construction simplifies hand prototyping and rework compared to SMD alternatives. The B57236S0100M000V9 uses a sintered metal-oxide NTC ceramic element optimized for high steady-state current handling and fast thermal response. As the body self-heats during steady-state operation, resistance falls to a low residual value, limiting continuous power loss to roughly 1 W at rated current; the trade-off is a finite cool-down period during which the limiter cannot absorb a second high-energy inrush. Designers must size the cold resistance to balance peak inrush against steady-state dissipation. Typical applications include switch-mode power supplies, motor soft-start circuits, UPS input stages, welding inverter input protection, and any mains-powered equipment with large bulk electrolytic capacitors. The wide operating temperature range and certified safety approvals make it a robust choice for industrial and consumer electronics. Compared to fixed resistors or mechanical NTC thermistor assemblies, the integrated leaded package reduces PCB area and assembly cost while maintaining repeatable thermal characteristics across production lots. When designing with this ICL, place it in series with the AC line ahead of the bridge rectifier and bulk capacitors, and verify the steady-state current (post-self-heating) does not exceed the 3.5 A rating under worst-case load. Add a bypass relay or PTC for repeated inrush events. According to the TDK datasheet, the device dissipates roughly 1 W at rated current after self-heating, so adequate airflow or lead spacing is essential for reliability. This page synthesizes distributor pricing from DigiKey/Mouser/LCSC, drop-in alternatives from TDK's B57236 family, and practical design notes not found in the manufacturer datasheet alone.
MF72-005D11 - 5Ω Inrush Current Limiter NTC | Cantherm | 4A
The Cantherm MF72-005D11 is a 5-ohm power NTC thermistor designed for inrush current limiting (ICL) applications, rated for 4 A steady-state current in a 13.00 mm through-hole disk package. Part of Cantherm's MF72 series of power NTC thermistors, it provides a cold resistance of 5 Ω ±20% that drops to a much lower hot resistance as self-heating occurs during the inrush event. The component is intended for use in series with the load on AC mains or DC power input rails to suppress the capacitor-charging surge that occurs when equipment is first switched on. A power NTC thermistor (Negative Temperature Coefficient) is a type of passive inrush current limiter whose resistance decreases as its body temperature rises. When current flows through the device at turn-on, I²R self-heating rapidly warms the disc, dropping its resistance by an order of magnitude within 1-3 seconds. Once steady state is reached, the low hot resistance minimizes continuous power dissipation. Power NTC thermistors sit in the broader hierarchy: NTC thermistor -> thermistor -> temperature-sensitive resistor -> passive component -> circuit protection, and are commonly deployed as a low-cost alternative to PTC resettable fuses and active MOSFET inrush circuits. Key specifications include 5 Ω nominal cold resistance, ±20% tolerance, 4 A maximum steady-state current, and a 13.00 mm (0.512 inch) disc diameter suitable for through-hole mounting. The MF72 series is RoHS compliant and is specified for operating temperatures typically between -55 °C and +200 °C. Because of its wide tolerance band (±20%), designers should verify worst-case cold resistance and peak surge current using the manufacturer I-V curves before selecting this part for high-margin designs. Typical applications include switch-mode power supply (SMPS) input stages, UPS systems, inverter soft-start circuits, audio amplifier power supplies, and industrial motor drives. The MF72-005D11's 5 Ω cold resistance is well suited to 120/240 VAC rectified rails feeding bulk capacitors in the 220-1000 µF range, where it can clamp the initial charging current to safe levels for downstream rectifiers and fuses. When designing with this device, place it on the AC line side of the bridge rectifier (not on the DC bus) and ensure adequate lead spacing for high-voltage isolation. Allow at least 60 seconds of cool-down time between power cycles to restore the cold resistance. For repeated fast-cycle applications, consider a higher-rated MF72 variant or an active inrush circuit using an NTC plus a bypass relay.