Llithium coin cells target the IoT

Llithium coin cells target the IoT

New Products |
By Rich Pell

The coin cells combine Murata’s standard and heat-resistant ‘CR’ range and the four decades of technology development of Sony’s battery operations that Murata acquired in September 2017. The high current ‘R’ range has twice the maximum pulsed discharge rating of conventional models at 50 mA (three seconds at 2V or higher, at 50 percent nominal capacity, 23 °C) and three times the discharge time (45 mA pulsed for three seconds, 23 °C).

These characteristics make the parts suitable for Low-Power Wide-Area (LPWA) communications devices, including LoRa and SIGFOX with their high peak current requirements. Available in CR2032 and CR2450 sizes with 3V nominal rating, the cells have nominal capacities of 200 mAh and 500 mAh respectively for discharge down to 2V.

New extended temperature types with the suffix ‘X’ are available in package sizes CR2032, CR2450, CR2477 and CR3677 and have an extended operating temperature range of -40 °C to +85 °C compared with standard types rated at -30 °C to +70 °C. The wider temperature range better matches the typical ratings of electronic parts in more challenging environments such as automotive, with a better cost-performance figure compared with types rated to 125 °C. Stored charge loss at high temperature is minimal over time and the CR3677X model delivers the highest capacity of any lithium coin cell, enabling smaller and thinner devices.

Although previously lithium cells have been seen as back-up supplies, the new ranges open up applications where the battery is the main power source. Typical uses are in the Internet of things (IoT), automotive and factory automation where LPWA networks are becoming common with sensors requiring local power supplies. The higher temperature range particularly suits outdoor applications such as smart meters, security and automotive, where the cells can replace conventional cylindrical types.

“Semtech’s LoRa RFIC SX1261 needs an approximately 25 mA power supply current at 3 V supply voltage and 42 mA at 1.8 V in order to achieve an output of ARIB-T108-compliant 20 mW. The LoRaWAN standard defines the maximum transmit time at 3 seconds,” said Vivek Mohan, Director of IoT at Semtech and a joint developer of LoRaWAN modules with Murata. ” With the high current type lithium coin cell battery, up to 50 mA and 3 seconds of current can be used, making it a promising solution for LoRaWAN-compatible small sensor nodes.”

Samples are available now and mass production is scheduled to begin in January 2019 (CR3677X end of 2019).

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