mCube tunes accelerometer for wearables

mCube tunes accelerometer for wearables

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By eeNews Europe

While the Internet of Things (IoT) has become much-used catchphrase, mCube CEO Ben Lee asserts that about 50 percent of the things attached to the Internet will be things that can move. These could be doors, door locks, windows, object tags, livestock monitors and so on. However, they will also need to be extremely low power to allow long battery life or operation from harvested energy.

The mCube technology is based the integraton of MEMS motion sensors above signal conditioning ASIC and hermetically bonding the two together using standard CMOS wafer processing. With bond pad connections contained in the contact points this can significantly reduce the number of wire bonds required which in turn can allow for a much more compact inertial sensor.

Bonded MEMS over ASIC accelerometer. Source: SystemPlus Consulting and mCube.

The MC3600 family of ultra-low power, 3-axis accelerometers is built upon this MEMS technology platform, which has seen 100 million units shipped, including 40 million in the last year.

The main difference between the MC3610 and the earlier devices is that there is a different optimization within the ASIC for low power with efforts made in both the software and hardware.

Stacked and wirebonded MEMS accelerometers. Source: SystemPlus Consulting and mCube.

Lee said the MC3610 has many modes of operation with sampling of the sensor at much lower frequencies than in a cell phone. While smartphone and gaming handsets need to sample at about 2kHz but for wearable and IoT applications that sample rate can taken down to between 125 and 25 samples per second, said Lee. At the same time a lot of attention has been paid to event detection and screening algorithms to make them more efficient, said Lee.

The result he claims is a tri-axis accelerometer that reduces power consumption by up to a factor of three compared with competitor devices and that reduces PCB footprint by a similar factor.

"mCube’s original family of motion sensors was designed for smartphones and tablets which have relatively large batteries," said Lee, in a statement. "With key input from leading device manufacturers, we developed the MC3600 family of accelerometers to extend battery life while keeping the footprint as small as possible, making them truly optimized for the wearables and IoMT market."

The MC3600 family of accelerometers will consume 1.1-micromps of current and comes in a 2mm by 2mm by 0.94mm 12-pin package. mCube is even looking at bare die delivery and glob-top packaging, Lee said. The MC3610 device has a configurable sample rate that can be set between 0.4 to 400 samples per second at 8-, 10-, or 12-bit resolution with a 32-sample FIFO, or 14-bits for single samples.

1 Single / FIFO, medium noise
2 Single / FIFO, low noise
Typ specs measured under VDD=1.8V, Temp=25

Low power wearable, IoT accelerometer. Source; mCube.

Its ultra-low power operating modes include a 0.6-microamp sniff mode, a 0.9-microamp 25Hz single-sample mode, and a 4.7-microamp 50Hz full operation mode. These advanced power modes, coupled with activity detection, enable IoMT devices to power-down other components during user inactivity, dramatically extending battery life.

The MC3610 is sampling now and is expected to be priced at less than 50 cents per unit in high volumes.

The EV3610A evaluation board provides the complete MC3610 pin-out and can be plugged into a standard DIL 10 socket. It comes ready-to-use with the required decoupling capacitor integrated into the board. It is available for purchase online at Mouser Electronics.

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