FXLS8967AF datasheet(90/98 Pages) NXP

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NXP Semiconductors

FXLS8967AF

3-Axis Low-g Accelerometer

Term

Description

Noise density and RMS-

integrated noise

Noise density is defined as the noise per unit of square root bandwidth and is typically

expressed in units of mg/√Hz or μg/√Hz for a consumer grade accelerometer. Noise is

measured with the device held stationary in a 1g field and isolated from environmental noise

and mechanical vibration. The RMS noise at a given ODR can be estimated as follows:

Nrms = ND * √BW

For example, in the ±2 g FSR, operating in HPM with an ODR of 400 Hz, the estimated RMS

noise would be:

Nrms = 280 µg/√Hz * √(400/2) Hz = 3.96 mg (~ 4 LSB).

Output data rate,

decimation factor, and

power consumption

The Output Data Rate (ODR) defines the rate at which acceleration data is output from

FXLS8967AF. Depending on the operating mode and ODR that is selected, different

decimation factors (oversampling ratios) are applied. The decimated output data is supplied

at the ODR rate, even though multiple samples of the sensor data may have been used to

calculate this average result. In FXLS8967AF lowest power mode, the decimation factor

is always 1, leading to the best power performance at the expense of the poorest noise

(resolution) performance. In high performance mode, the decimation factor is automatically

increased to the maximum possible value for a given ODR, resulting in the best noise

(resolution) performance at the expense of the poorest power consumption. In motion

detection mode with BT_MODE=VDD, use of HPM or FPM mode is not advised. Only the

default LPM mode should be used.

Primary

Device that initiates and drives the communication with secondary devices.

Secondary

Device or devices that responds to communication initiated by primary device.

Self-Test

The integrated self-test function can be used to verify correct transducer and signal chain

operation without the need to apply an external acceleration stimulus. When the self-test

function is activated for each axis, an electrostatic actuation force is applied to the proof mass,

simulating a small change in acceleration. The self-test function of the device is independently

exercisable for each axis, along with a selectable displacement direction (polarity). The device

need not be static while exercising the self-test function as it is insensitive to any external

physical acceleration. Refer to AN5311[2] for more details on self-test.

Sensitivity

The accelerometer sensitivity, also known as scale-factor, represents the change in

acceleration input corresponding to 1 LSB change in output and is typically measured in either

mg/LSB or LSB/g.

Zero-g offset

The accelerometer zero-g offset describes the deviation of the sensor output from the ideal

0g value when no motion or gravity is acting on it. With an accelerometer stationary and

placed on a level, horizontal surface, the ideal output is 0 g for the X and Y axes. Likewise,

if the accelerometer is placed on a vertical plane, the ideal output is 0 g for the Z-axis. The

deviation of each output from the ideal value is called zero-g offset. Offset is, to some extent,

a result of stress on the sensor and how well the sensor is leveled when soldered to the

board. Therefore, the zero-g offset can change after mounting the sensor onto a printed circuit

board or exposing it to extensive mechanical stress.

For applications that require increased precision, any residual post-board mount offset may be

removed using the

OFF_X/Y/Z registers, or alternatively, in the host application software.

Table 121. Glossary...continued

21 References

[1] AN1902 — Assembly Guidelines for QFN and DFN Packages, http://nxp.com/files/analog/doc/app_note/AN1902.pdf

[2] AN5311 — FXLS8962AF self-test procedure, https://www.nxp.com/docs/en/application-note/AN5311.pdf

[3] UM10204 — I2C-bus specification and user manual, http://www.nxp.com/documents/user_manual/UM10204.pdf

FXLS8967AF

All information provided in this document is subject to legal disclaimers.

Objective data sheet

Rev. 1 — 27 April 2021

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