ICM-42688-P

The ICM-42688-P is a high-precision 6-axis MEMS MotionTracking device manufactured by TDK InvenSense, combining a 3-axis gyroscope and a 3-axis accelerometer in a 2.5 x 3.0 x 0.91 mm LGA-14 package. It is the industry’s first IMU to support 20-bit data format in FIFO, encapsulating 19-bit gyroscope data and 18-bit accelerometer data for high-resolution motion sensing.

The gyroscope offers programmable full-scale ranges from +/-15.625 to +/-2000 dps with 0.5% sensitivity error and 2.8 mdps/sqrt(Hz) rate noise density. The accelerometer offers programmable full-scale ranges from +/-2g to +/-16g with 0.5% sensitivity error and 70 ug/sqrt(Hz) noise density. Low-noise 6-axis current consumption is 0.88 mA.

The device supports external clock input (31 kHz to 50 kHz) for reducing system-level sensitivity error and improving orientation measurement accuracy. On-chip APEX Motion Processing engine provides pedometer, tilt detection, tap detection, wake-on-motion, raise to wake/sleep, and significant motion detection functions without host CPU intervention.

Communication interfaces include I3C (12.5 MHz), I2C (1 MHz), and SPI (24 MHz). A 2 KB FIFO buffer enables burst data reads, reducing host CPU load. The device operates from VDD and VDDIO of 1.71V to 3.6V, across -40 to +85C. It features 20,000g shock tolerance and is RoHS and Green compliant. ECCN: EAR99. Product status: In Production. Standard packaging: 5,000 pcs/reel.

The ICM-42688-P operates as a 6-axis inertial measurement unit with the following subsystem architecture:

1. MEMS Gyroscope: Three independent MEMS vibratory gyroscope elements measure angular rate around the X, Y, and Z axes. Each element uses the Coriolis effect — when a vibrating mass rotates, the Coriolis force produces a proportional displacement perpendicular to both the vibration and rotation axes. This displacement is capacitively sensed and converted to a digital signal by 16-bit ADCs. Eight programmable full-scale ranges (±15.625 to ±2000 dps) trade off resolution vs. dynamic range.

2. MEMS Accelerometer: Three independent MEMS accelerometer elements measure linear acceleration along X, Y, and Z axes using capacitive displacement sensing of proof masses suspended by silicon springs. Four programmable full-scale ranges (±2g to ±16g) are available. The 18-bit resolution in FIFO mode provides high-precision data for orientation and motion analysis.

3. Signal Processing: Raw sensor data passes through user-programmable digital low-pass filters for both gyroscope and accelerometer channels. A dedicated temperature sensor enables thermal compensation. The 2 KB FIFO buffer stores processed sensor data in 20-bit format, supporting burst reads to minimize host CPU overhead.

4. APEX Motion Engine: An on-chip hardware accelerator processes sensor data in real-time to detect motion events without host CPU intervention. Functions include pedometer (step counting), tilt detection (>35 degrees), tap detection (single/double), wake-on-motion (accelerometer threshold), raise-to-wake/sleep (gesture), and significant motion detection. These generate programmable interrupts on two interrupt pins.

5. External Clock Input: An optional external clock (31-50 kHz) can be fed to the device to synchronize the internal sample rate, reducing sensitivity drift due to temperature variation and device-to-device variation. This is critical for precision orientation estimation in AR/VR and robotics.

6. Host Interface: The configurable interface supports I3C (up to 12.5 MHz SDR / 25 MHz DDR), I2C (up to 1 MHz), or SPI (up to 24 MHz). Interface mode is selected at power-up via the AP pin state.