A new family of low-power, three-axis accelerometers could
bring orientation detection and gesture recognition to a broader array of
products, from mobile phones and games to pedometers and MP3 players.
With active current draw as low as
6 µA, the new family of accelerometers is expected to be especially important
in mobile applications, where battery power is at a premium. "We're seeing a
lot of interest in mobile phones, which is now the biggest market for
accelerometers," says Bryce Osoinach, product line manager for Freescale Semiconductor's inertial sensor
products. "Most mobile phones now have orientation detection and many are
starting to add gesture recognition for more complex gaming routines."
The family of accelerometers, which
is made by Freescale, includes a 14-bit device called the MMA8451Q
that offers higher resolution for applications needing faster and more precise
motion detection. The 14-bit technology could be particularly important for
gaming applications on mobile phones, where users tend to employ smaller
amounts of tilt and make quicker motions than they would in a full-sized,
physical game. Freescale engineers say that the MMA8451Q's low-noise operation
allows for more precise motion detection on very small degrees of tilt.
"For gaming applications, this allows
the system to respond with much less tilt, which gives you a much more accurate
feeling," Osoinach says. "So instead of 15 degrees of tilt, now you might
reduce it to just five."
He expects the low current draw of
the devices to be equally important. In a low-power mode, the devices draw just
1.6 µA at 12.5 Hz. They also pull 166 µA at 800 Hz in a normal power mode.
Freescale says that the MMA845xQ can achieve four days of battery life in a
typical polling application where the device is continuously on.
"The power is extremely low,"
Osoinach says. "These devices have come in at (current draw) numbers we've
never seen before."