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MEMS oscillator extends wearable battery life

Posted: 05 Jun 2014 ?? ?Print Version ?Bookmark and Share

Keywords:MEMS? wearable? battery? oscillator?

Mobile devices are constantly on idle state, however, they still wake up periodically to perform monitoring tasks involving button clicks, Wi-Fi activity, Bluetooth connection, and battery supervision functions.

During those operations SiTime Corp. claims its new, high-precision, real-time clock can save 50 per cent or more of the power usually expended during idle time, at least doubling the battery life during those periods.


Figure 1: SiTime's super-accurate temperature compensated MEMS oscillator (TCXO) helps extend battery life of wearables by allowing smaller sampling windows for sensors, Bluetooth, and WiFi, among others. Source: SiTime

"These power savings might not amount to much for a device with a big battery, but for Internet of Things and wearable devices with tiny batteries, their lifetime can be significantly extended with our new SiT1552 MEMS 32kHz TCXO [Temperature Compensated Oscillator] real-time clock," Piyush Sevalia, executive vice president of marketing, told EE Times.

Every mobile device has a 32kHz real-time clock to keep track of time, telling its device when to wake up and perform its duties. Most of these real-time clocks have a precision of 100ppm to 250ppm, which is adequate to keep a device from seeming unresponsive or sluggish. However, for real-time devices like Bluetooth accessories, even 20ppm means that the software designers have to include buffer time to make sure the external device is connected properly before data is transferred.

In essence, this means the software designers add extra time at the beginning of a wakeup operation to make sure both devices are communicating, then more extra time at the end of an operation before the device is put back in idle mode to make sure all the data was transferred. However, with SiTime's SiT1552 TCXO real-time clock, its accuracy is within 5ppmthe lowest in the industrypermitting the software writers to drastically cut down those buffer periods, thus saving power and extending battery life, especially for wearables.

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