The world's first industry's lowest power MEMS ultrasonic sensor delivers millimeter-precision distance

The MEMS-based miniature "silicon chip sonar" device provides millimeter-accurate distance sensing with the industry's lowest power consumption. This MEMS ultrasonic sensor can be used for distance measurement, position tracking, presence detection, and obstacle avoidance applications in consumer electronics, robotics, and drones.

Ultrasonic time-of-flight (ToF) sensors are generally considered to be the best distance sensors for automotive, industrial, and drone and robotic applications. It has many advantages over optical sensors or infrared sensors. It provides the most accurate distance measurement, is not affected by the size or color of the target object, is not affected by environmental noise, and can be used in direct sunlight. These advantages, along with ruggedness, precision and reliability, make ultrasonic sensors widely used in industrial and automotive applications.

However, until today, ultrasonic sensors still require complex signal processing and are not suitable for consumer electronics due to their large size.

One thousandth of the size, one hundredth of the power consumption

Now, TDK has introduced a MEMS-based miniature ultrasonic sensor that offers the same performance and reliability compared to traditional ultrasonic sensors, but with a size that is only one-thousandth of that of conventional products, and its power consumption is as low as traditional. One percent of the product. This miniature sensor is small in size and can be integrated into compact consumer products for ultrasonic detection

For example, in smartphones and wearables. When measuring distance, the sensor first transmits an ultrasonic pulse and then monitors the reflected echo of the target within the field of view of the sensor. Each echo is transmitted at the speed of sound, and the distance from the sensor to the target can be accurately measured by measuring the flight time of the echo.

Figure 1: Top and bottom of the MEMS ultrasonic sensor (left). This sensor block diagram shows a CMOS system-on-chip (SoC) connected to a piezoelectric MEMS ultrasonic sensor (PMUT).

Currently, there are two products that provide engineering samples to customers, namely CH-101 with a maximum sensing range of 100 cm and CH-201 with a maximum sensing range of 500 cm.

Long range sensor. These micro devices are housed in a compact 3.5 mm x 3.5 mm LGA package with a piezo MEMS ultrasonic sensor (PMUT) and custom

The CMOS System-on-Chip (SoC) combines to complete all ultrasonic ToF signal processing (Figure 1). Both CH-101 and CH-201 use 1.8 V

Powered by a power supply and with a convenient I2C interface for easy integration into consumer electronics.
High precision distance measurement performance and wide field of view

Despite its small size, this new MEMS ultrasonic sensor delivers outstanding performance. For example, CH-201 measures signal noise at a distance of 120cm is only 0.35

Mm (1¦Ò), which is one percent of the noise of the competing infrared ToF sensor. In addition, the CH-101 and CH-201 offer a field of view (FoV) up to 180¡ã, so the entire spatial extent can be detected with just one part. A variety of housing reference designs are also available to allow the customer to focus and direct the ultrasound beam by changing the shape of the area around the acoustic port of the sensor to achieve the desired horizontal and vertical field of view.

Distance from 120cm to noise target distance field of view with narrow field of view housing

Figure 2: The distance noise of the CH-201 sensor is only one percent of the traditional infrared ToF sensor (left). A narrow field of view enclosure is one of the available reference designs that can be shaped to achieve the desired field of view (right).

An ultra-low-power system-on-a-chip (SoC) controls the entire ToF process: sending ultrasonic pulses, digitizing the received ultrasound echoes, detecting ToF to the nearest target and passing I2C

Returns a 16-bit ToF signal. The System-on-Chip (SoC) enables the wake-up detection application to be always active; the total current consumption is as low as 8 ¦ÌA with 1 sample measurement per second. Since the driver is written in C, developers can easily use CH-101 and CH-201 in embedded systems. In addition, a single microcontroller can control multiple CH-101 and CH-201 sensors, enabling complex multi-sensor measurements.

Extremely wide range of potential applications

The new MEMS ultrasonic sensors are the products of choice for applications such as drones and robots. In this type of application, other types of distance sensors do not provide the required performance. They are also ideal for smart home products such as smart speakers, where passive infrared (PIR) and optical proximity sensors are not as effective as ultrasonic sensors. This miniature ultrasonic sensor also accurately tracks objects, such as tracking handheld game controllers in virtual reality and augmented reality (VR/AR) systems. Smartphones are another important area of application: Thanks to the wide field of view of the CH-101, accurate distance measurements can be made even on the top or bottom of the phone, so designers can omit the optical proximity sensor on the front of the phone to implement the phone. Full screen design.

In distance measurement and object detection applications, designers previously forced to choose between large-size ultrasonic sensors and laser-based infrared ToF sensors can now benefit from the capabilities of new ultrasonic sensors:
• Provide accurate, low-latency distance measurement with up to 100 samples per second and position noise less than 1mm
• Sensors are always active in applications such as personnel proximity, movement and activity detection, with power consumption as low as 15¦ÌW
• The field of view of the object is detected up to 180¡ã, so one sensor can detect the entire room scene
• Works flawlessly in all lighting conditions, even in direct sunlight
• Detects objects of any color, including transparent objects, improves target detection
• Protect your eyes by avoiding the use of laser-based infrared sensors