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To prevent current flows that can influence the performance of the MTi 1-series, it is recommended to remove all copper (planes) underneath the MTi 1-series as shown in the image below.
Layout example
The MTi 1-series module uses a right-handed coordinate system as the basis of the sensor frame.
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Default sensor fixed coordinate system for the MTi 1-series module
The accelerometer determines the origin of measurements. The images below show the location of the accelerometer of the MTi 1-series.
Location origin of measurements for HW version 2.x (left) and 3.x/5.x (right)
In general, it is recommended to place the MTi 1-series module in an area on the PCB with minimal mechanical stress. The following paragraphs show causes of mechanical stress and ways to reduce it.
Pushbuttons induce mechanical stress when used. Therefore, it is recommended to keep a reasonable distance between a pushbutton and the MTi 1-series module.
Anchor points are usually a cause of mechanical torsional stress. The MTi 1-series module should not be placed near an anchor point. Furthermore, since a plane is uniquely determined by three points, it is recommended to affix the PCB with no more than three anchor points. More than three anchor points over define the PCB plane and therefore induce mechanical stress. The image below shows an example of a PCB with four anchor points that gives a maximum stress in the centre of the diagonal crossover. Avoid placing the MTi 1-series module in such an area.
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High mechanical stress in diagonal crossover between anchor points
The best way to deal with the problem shown in the image above is to remove one of the anchor points as shown in the image below. This will reduce the overall stress in the PCB. If more anchor points are required (e.g. in case of a large PCB), the MTi 1-series module should be moved to an area with minimal mechanical stress, as shown in the second image below.
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Reducing anchor points to reduce overall stress in the PCB
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Keeping the MTi 1-series module away from high mechanical stress areas
The MTi 1-series features an industry-leading signal processing pipeline (AttitudeEngineTM) which rejects vibrations. For best results, however, it is recommended that the MTi 1-series is mechanically isolated from vibrations as much as possible. Especially in applications where vibrations are likely to occur, the anchor points of the PCB that holds the MTi 1-series module should be dampened. The required type of dampening varies from application to application.
Keep the MTi 1-series module away from heat sources. Thermal gradients can cause mechanical stress, which can affect the sensor performance of the MTi 1-series.
For best performance, it is best to solder the module directly onto a PCB by a solder reflow process. When placed in a socket, the module may be subjected to mechanical stress by the springs in the socket, which might result in deteriorated performance.
The MTi 1-series uses a 3D magnetometer for measuring the geomagnetic field. This part is sensitive to magnetic disturbances.
Ferromagnetic materials can be magnetized and the magnetic behaviour can change during operation. This behaviour will influence the measurements of the 3D magnetometer of the MTi 1-series. Therefore, keep these ferromagnetic materials away from the MTi 1-series.
High current power lines on the PCB will introduce magnetic fields that will influence the measurements of the 3D magnetometer of the MTi 1-series. Place high current power lines away from the MTi 1-series.
Example: a power line with a current of 100 mA at a distance of 10 mm will introduce an error of 2 µT.
The footprint of the MTi 1-series module is similar to a 28-lead Plastic Leaded Chip Carrier package (JEDEC MO-047). Although it is recommended to solder the MTi 1-series module directly onto a PCB, it can also be mounted in a compatible PLCC socket (e.g. 8428-21B1-RK of 3M, as used on the MTi 1-series Development Kit). When using a socket, make sure that it supports the maximum dimensions of the MTi 1-series module as given in Package Drawing (note the tolerance of ± 0.1 mm).
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Recommended MTi 1-series module footprint