Freescale Semiconductor DEMOMMA8491 User guide

Freescale Semiconductor Document Number: AN4292

Application Note Rev 0, 10/2012

DEMOMMA8491 Xtrinsic Accelerometer Evaluation Kit

by: FengYi Li

Applications Engineer

This application note provides an overview of the
Xtrinsic DEMOMMA8491 kit and its evaluation
guidelines.

The DEMOMMA8491 kit contains two boards:

• Demo board: provides a tamper detection sensor
demonstration using the Xtrinsic MMA8491Q
45° tilt sensor and 3-axis accelerometer, housed
in a transparent plastic case.

• Breakout board: provides easy access to every
pin of the QFN sensor for evaluation.

This document describes board functionality and
features, how to use these boards, and what to look for
when evaluating the devices. The last section provides
reference schematics and the bills of materials.

Contents

1 DEMOMMA8491 Demo Board . . . . . . . . . . . . . . . . . . . . 2

1.1 Acceleration directions . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Using the demo board . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 Acceleration values are cumulative. . . . . . . . . . . . . 3

2 DEMOMMA8491 Breakout Board . . . . . . . . . . . . . . . . . . 4

2.1 Pin map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2 Suggested application connections . . . . . . . . . . . . . 5

2.3 Soldering considerations . . . . . . . . . . . . . . . . . . . . . 5

2.4 Evaluating performance. . . . . . . . . . . . . . . . . . . . . . 6

3 Schematics and Bill of Materials (BOM) . . . . . . . . . . . . . 6

3.1 Demo board schematic . . . . . . . . . . . . . . . . . . . . . . 6

3.2 Demo board BOM . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.3 Breakout board schematic. . . . . . . . . . . . . . . . . . . . 7

3.4 Breakout board BOM . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

© 2012 Freescale Semiconductor, Inc. All rights reserved.

1 DEMOMMA8491 Demo Board

The demo board of the DEMOMMA8491 kit is an out-of-the-box 3-axis MEMS tilt sensor. It showcases
a simple tilt sensor implemented with the MMA8491Q device, with 10 additional passive components.

Figure 1. DEMMMA8491 demo board

1.1 Acceleration directions

The demo board uses the acceleration directions in Figure 2. The left image shows the acceleration
direction on the MMA8491Q device. The right image shows the acceleration direction of the demo board.

Figure 2. Sensor orientation

1.2 Using the demo board

The demo is powered by a 3V coin battery and is controlled by one switch button (SW1). When the switch
is pressed, the tilt sensor is powered on, and it takes one sample of the current acceleration. The tilt
detection result is simultaneously displayed with 3 LEDs (each LED is paired with one of the X, Y, Z axes).
A lit LED indicates that a tilt angle greater than or equal to 45° is detected on that axis.

DEMOMMA8491 Xtrinsic Accelerometer Evaluation Kit, Rev 0

2 Freescale Semiconductor, Inc.

To demonstrate the kit, hold the demo board to the desired position, then press and hold down the switch

• LED X = 0 indicates that LED X
is turned off.

• LED X = 1 indicates that LED X
is turned on.

button. Make sure that your hand is steady. Observe the LEDs for a tilt report. Release the button to discard
the sample.

Figure 3 shows the LED status at 6 different orientations.

Figure 3. LED states for different orientations

1.3 Acceleration values are cumulative

The MMA8491Q device is a MEMS-based accelerometer. It picks up the acceleration signal (if it is
present), and compares the acceleration to an internal threshold of 0.688g. When the demo board is held
at a 45° angle, the acceleration reading along that axis (coming from the earth gravity) is about 0.688g. In
this case, that axis's output (XOUT, YOUT or ZOUT) is triggered to logic high.

When you provide external acceleration (other than the earth gravity) on the demo board, the tilt sensor
reports the cumulative acceleration. As the result of these additional g-forces, you might observe positive
tilt detection when the board is at a position less than a 45°angle.

DEMOMMA8491 Xtrinsic Accelerometer Evaluation Kit, Rev 0

Freescale Semiconductor, Inc. 3