MEMS timing device cracks cellphone market: Page 2 of 3

November 04, 2013 // By R. Colin Johnson, EE Times
Micro-electromechanical system (MEMS) chipmaker Sand 9 Inc., of Cambridge, Massachusetts, claims to have finally cracked the multibillion unit mobile phone and Internet of Things market with a piezo-electric design that provides the performance lacking in traditional MEMS timing chips. More than five years in the making, Sand 9 has finally announced its first piezo-electric timing chips, for which it already has mobile phone customers lined up.
with no external compensation.

Sand 9 is targeting the wireless applications market being served by high-end quartz temperature compensated crystals (TCXO), especially those used by a mobile phone’s cellular transceivers, power management ICs, GPS, WiFi, FM, Bluetooth, and accessories using the low-power version called Bluetooth Smart.

Its first two timing chips will be the TM061 MEMS resonator (MR) and TM361 temperature-sensing MEMS resonator (TSMR). Both devices use a sub-millimeter package size (0.76- x 0.84- x 0.5-mm) which Sand 9 claims is 50 percent smaller than the smallest quartz crystal in the industry and 10-times more resistant to shock.

The 48-MHz TM061, which targets Bluetooth Smart applications, is a resonator with a dummy cap instead of an ASIC, making it the ultra-low-cost solution. The 76.8-MHz TM361 also uses a dummy cap, but includes within the material stack a temperature sensor (thermistor) and heater for sophisticated compensation and calibration of the resonator. Integrating the thermistor into the MEMS resonator gives it 10 times better thermal coupling than quartz, which must use an external thermistor. The heater allows the TM361 to be quickly calibrated by the original equipment manufacturer (OEM). For the future, Sand 9 plans a follow-on device which integrates the phase-locked-loop (PLL) needed for a complete piezo-electric MEMS oscillator.

“Our future road map includes a temperature-sensing MEMS oscillator (TSMO), which integrates the oscillator circuitry into the silicon cap,” said Borkowski.

Sand 9’s chips will be manufactured in two foundries — GlobalFoundries for the MEMS portion and IBM for the application-specific integrated circuit (ASIC) — after which the two chips will use wafer-scale bonding, so that the ASIC carrying the electronics serves double duty by also capping the MEMS chip to prevent environmental contamination.

The big surprise is that, unlike quartz, Sand 9’s MEMS resonators and oscillators can be over-molded into the same package as the device for which they are providing timing signals. In fact, Sand 9’s business model is to

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