 Hello, and welcome to our presentation about ST's MEMS gyroscopes. In this presentation, we will review how MEMS gyroscopes are developed and produced at ST, their main applications, their internal structure and working principles, and details on how to use them for your application. First, what are MEMS gyroscopes exactly? While accelerometers measure linear acceleration as long as there is no rotation, MEMS gyroscopes generate an output signal directly proportional to the angular rate applied to the device. To do this, they measure the force generated by what is known as the Coriolis effect. If you are not already aware of this principle, please check our quick reference towards the end of this presentation. When an accelerometer is rotated, the projection of gravity acceleration is measured as well and there is no way to distinguish between the two different contributions. By using a gyroscope, angular rotations are measured, while linear displacements are not. Accelerometers and gyroscopes can be combined to create an inertial measurement unit or IMU. An ST MEMS gyroscope combines the MEMS sensor itself and an ASIC to process the sensor output integrated in a single micromachined structure. To achieve a very high level of integration, ST uses a system-in-package approach where the ASIC part is stacked on top of the MEMS structure to address applications where small size is a key constraint. The MEMS sensor is composed of a mass, which is kept in a continuously oscillating movement so that it reacts to the Coriolis effect when an angular rate is applied to the device. A CMOS ASIC measures the angular rate of the MEMS element relative to the external world and delivers an analog output voltage proportional to that rate. To give you a more detailed view of our implementation expertise, here we have a detailed view of the MEMS structure of a single axis gyroscope. In the photo, we see the mechanical mass with its two wings highlighted in yellow. The wings move up and down when an angular rate is applied. Capacitive plates surround the structure and are used to actuate the mass. The diagram on the right shows a representation of this structure along with the capacitive plates that are used to create the motion. The cross sections at the bottom show, on the left, wing behavior when no angular rate is applied and, on the right, when an external angular rate is applied. The wing displacement is read by detecting the capacitive variation between the bottom plate and the wing itself. With this structure, we consider that ST has reached the state of the art for this type of product. Gyroscopes were once too big, too power-hungry, and too expensive for consumer applications. Recent MEMS gyroscopes have paved the way to a completely new set of innovative applications. They can be used to implement new advanced user interfaces and give the user an improved gaming experience. For these applications, a full-scale range of thousands of degrees per second or DPS is required to capture the player's rapid movements. At the other end of the application spectrum, image stabilization for digital, still and video cameras only needs 30 DPS and very low noise and high stability over temperature as key parameters. ST's gyroscope offering is able to cover all the main applications with the widest portfolio of single and multi-axis gyroscopes now available on the market. Let's have a quick look at ST's family of standalone, multi-axis gyroscopes. ST offers the widest choice of full-scale ranges in the market, from 100 DPS, suitable for image stabilization in digital still camera and video camera, up to 6,600 DPS for improved user experience in gaming and user interface applications. ST OIS gyroscope is the smallest package in the OIS market, offering an excellent rate noise density, top-level performance, and low power consumption. Each OIS gyroscope integrates a temperature sensor for best-in-class temperature compensation for photos with high quality, improving the long exposure time pictures. These charts show ST's family of combo devices with multi-axis gyroscopes. ST's gyroscope in combo devices is an ultra-low power solution for always-on applications combined with best-in-class performance. At ST, we focus on a set of key features to guarantee that we provide the best-in-class design. Let's have a quick look through these features, for example, zero-rate control, sensitivity, and so on, to see how ST performs. So first, a quick explanation of the terminology that we use to describe how a gyroscope rotates in three axes. There are two in-plane axes called pitch and roll, the X and Y axes. The third is an out-of-plane axis called yaw, the Z axis. So linking in with our previously mentioned key features, zero-rate level refers to the analog or digital sensor output value when no angular rate is applied. Sensitivity always refers to the ratio between the output and input of the sensor. ST's gyroscope family provides the industry's best zero-rate level stability over an extended temperature range of minus 40 to plus 85 degrees Celsius. Thanks to this excellent performance, which also applies to the sensor's sensitivity, users can save cost and effort otherwise needed for temperature compensation in their products. A complete understanding of the main parameters associated with MEMS gyroscopes and their representation in the datasheet is very important in order to fully exploit the advanced performances provided by these products. Zero-rate level is the output of the sensor when no angular rate is applied. This parameter is indicated by a typical value and specified over a certain accuracy range. Temperature variation could affect the sensor output even when there is no external stimulus. The temperature characteristic is also reported here to provide the user with a more complete comprehension of possible drifts. Sensitivity is defined as the ratio between the output and input of the sensor. In the case of digital output gyroscopes, sensitivity is usually expressed as DPS per LSB. As for the zero-rate level, sensitivity is also reported both at ambient temperature and over the device's specified temperature range. Temperature characteristic is also reported to provide the user with a complete comprehension of possible drifts by simply subtracting the zero-rate level from the output value and dividing the result by the sensitivity expressed in MDPS over LSB, we obtain the angular rate applied to the gyroscope. The sensitivity of ST's gyroscopes is also characterized by the excellent temperature stability with a variation of a fraction of a percent for each degree Celsius. The third main parameter to consider when dealing with sensors in general and gyroscopes in particular is the rate noise density. This parameter is usually expressed in the form of spectral density, allowing the user to get the actual value of the noise depending on the low-pass filter applied to the output. The output noise will vary depending on the bandwidth. Reducing the bandwidth through low-pass filtering helps improve resolution measurement. The highlighted formula shows that by multiplying noise density by the square root of the bandwidth, the RMS value expressed in degrees per second can be immediately retrieved. Noise is usually expressed in terms of rate noise density, MDPS over square root of the frequency, allowing the user to evaluate, depending on the bandwidth selected, which is the final noise level. The table in the bottom center of the screen can be used to convert this value to the related peak-to-peak level. To summarize, ST's consumer gyroscope family provides the customer with unrivaled performances. The excellent low-noise level makes ST's gyroscopes perfectly suited for applications requiring high-resolution angular rate sensing. So now that we've been through the high-level view, let's check out some of the technical detail behind how MEMS gyroscopes work. This may help you in deciding whether MEMS gyroscopes are the right component for your product. As said previously, ST's MEMS gyroscopes use the Coriolis force to measure angular movement. When a mass moves in a particular direction with a velocity v and an external angular rate is applied, see the red arrow. The Coriolis effect generates a force shown here with the yellow arrow that causes a perpendicular displacement of the mass. The value of this displacement is directly related to the angular rate applied. This displacement is read by measuring variations in capacitance, a robust and reliable technique successfully used across ST's MEMS product lines. In practice, ST's MEMS gyroscopes use two equal masses that are kept oscillating so that they are always moving in opposite directions, much like a tuning fork. When the system rotates, the Coriolis forces on the two masses are always in opposite directions and the angular movement is measured using the difference in capacitance between the two sides. When a linear acceleration is applied to the sensor, both masses move in the same direction, so there is no difference in capacitance on each mass, so the result is zero. Compared to a single mass approach, the differential nature of the tuning fork makes the system intrinsically insensitive to undesired linear acceleration or vibrations acting on the sensor, and so only measures the angular rate. For the Coriolis effect to work, the driving mass must be kept under continuous movement. This is achieved with an oscillation that is regulated and guaranteed by a dedicated portion of the ST-ASIC circuitry. As soon as an external angular rate is applied to the sensor, shown by the red arrows, two separate and flexible wings cut inside the mass move up or down, depending on the direction of the angular rate applied. Note that as one wing moves up, the other moves down. The distance traveled by the wings is measured to provide the angular rate. Thank you for following this presentation. Data sheets and application notes on the ST-MEMS gyroscope and evaluation boards are available online from our dedicated page at st.com.com.