A six-axis inertial measurement unit (IMU) combines a three-axis gyroscope and a three-axis accelerometer to provide angular rate and acceleration data for orientation estimation and motion detection. The ICM-42688-P, ICM-42605, and ICM-42686-P from TDK InvenSense share similar interfaces and packages. Their main selection differences are gyro noise, full-scale range, output data rate, and operating current.

Parameter Comparison

All three devices use a 14-pin LGA package measuring 2.5 × 3.0 × 0.91 mm nominally and operate from −40 to +85°C. VDD and VDDIO each support 1.71–3.6 V. Each device provides I²C, SPI, and I3C interfaces and a 2 kB FIFO.

Application Fit

• ICM-42688-P

Suitable applications: AR/VR controllers, head-mounted devices, and robots that require low gyro noise or a more stable sampling time base.

Selection focus: This device has the lowest typical gyro noise density of the three. A precise, stable external reference clock can reduce the effect of internal time-base variation on ODR. Orientation performance still depends on mounting, calibration, filtering, and sensor fusion.

• ICM-42605

Suitable applications: Portable devices, smart watches, fitness trackers, and game controllers whose required motion ranges and output rates fall within the device’s capabilities.

Selection focus: It has the lowest typical six-axis low-noise operating current in this comparison. Consider it when external clock input and an extended FIFO data format are unnecessary. Battery-life estimates must also account for the actual ODR, duty cycle, and host wake-up frequency.

• ICM-42686-P

Suitable applications: Golf and tennis swing analysis and connected sports equipment where motion peaks may exceed ±2000 °/s or ±16 g but remain within its ±4000 °/s and ±32 g ranges.

Selection focus: The wider full-scale ranges reduce the risk of measurement saturation. Compared with the other two devices, each count represents a larger physical change when all use 16-bit output at their respective maximum ranges. Select the range according to expected peaks and the required ability to resolve small changes.

Design Considerations

• Extended FIFO data uses fixed full-scale ranges

Both the ICM-42688-P and ICM-42686-P use 20-bit fields in the extended FIFO format to carry 19 bits of actual gyro data or 18 bits of actual accelerometer data; the remaining low-order bits are zero. This format does not establish 20-bit measurement accuracy. When enabled, the operating ranges are fixed at ±2000 °/s and ±16 g for the ICM-42688-P, and ±4000 °/s and ±32 g for the ICM-42686-P, regardless of other range selections in the registers.

• Evaluate noise and current at the intended settings

Choose ODR and filter settings for the frequency content of the target motion, then assess noise and latency. Maximum ODR does not imply minimum power consumption. Accelerometer low-power current must also be distinguished from six-axis low-noise current. At high ODRs, check bus throughput and the FIFO service interval.

• Check clock pin use and software configuration

Pin 9 on the ICM-42688-P and ICM-42686-P selects CLKIN, INT2, or FSYNC. When configured as CLKIN, it cannot also serve as INT2 or FSYNC. Check reserved-pin connections, WHO_AM_I, range encoding, sensitivity, FIFO parsing, and initialization when changing devices. Similar packages and interfaces do not establish drop-in compatibility.

• Confirm motion functions against the applicable revision

All three devices provide APEX functions such as step counting, tilt detection, tap detection, and wake on motion. Revision 1.9 of the ICM-42688-P datasheet removes Raise to Wake/Sleep.

Product Summary

First exclude devices that cannot meet the required motion range or output rate. Then compare noise, operating current, and external clock requirements. Validate temperature performance, interface configuration, and software compatibility on the prototype. Visit WIN SOURCE to check current inventory and pricing.