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Murata launches chip PTC thermistors, IF ceramic filter

Smyrna, GA-based Murata Electronics North America has introduced a line of chip PTC thermistors and an IF ceramic filter, both for automotive applications.

Optimized for an operating temperature of 105 degrees C or less and available in 42 Ohm and 22 Ohm automotive grade, Murata’s PRG21_S1 series thermistors offer small case size (0805) and a reset capability for circuits having a sensor line or low power line (<25 mA) that require over-current protection. Examples include air bag ECUs, remote keyless entry (RKE) receivers, electrical power steering ECUs, engine control ECUs, immobilizers, tire pressure monitoring system receivers, and car audio systems. The chip thermistors also protect IC and power supply units from trouble caused by circuit-shorting modes, according to senior product specialist Akiyoshi Okawa.

Customers don’t need to replace PRG21_S1 thermistors when a fuse blows, Okawa says, adding that, compared with resettable fuses based on polymer PTC thermistor technology, chip thermistors offer better resistance value stability. "Chip thermistors) are ideal for automotive engineers because they make it easy to downsize, don’t need to be repaired or replaced, and eliminate worry about a reduction of power gain."

Targeting tire pressure monitoring receivers, RKE receivers and two-way RKE systems, AM/FM radios, RFID and data telemetry applications, Murata’s 10.7 MHz SFECF10M7 IF filter offers high environmental reliability and a smaller package size for automotive engineers developing wireless applications. Tom Cho, product manager for piezoelectric devices, says the filters can withstand 1,000 cycles of thermal shock while operating over the -40 degree to +125 degree C automotive temperature range within the 150 kHz to 450 kHz bandwidth. Cho adds that the filter’s small footprint allows more room for integrating functions into a single device.

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