As the sensing component of the front-end, smart sensing technology plays an important role in smart manufacturing and IoT. To achieve environmental sensing and signal converting, various sensors are required, particularly in smart wearable field, there will be a stronger reliance on sensors, requiring sensors to evolve towards intelligence, miniaturization, and multifunctionality.

MT3502, newly launched by Maxic, is a high performance, low-power dissipation optical tracking sensor featuring rotation and key detections and integrating 850nm VCSEL emitter, infrared receiving array, high-accuracy ADC and high-speed digital image processing module. Based on the laser navigation techniques, MT3502 measures changes in position by optically acquiring sequential surface images and mathematically determining the speed, so as to realize real-time, micro-distance, high-performance, ultra-low power movement and rotation angle detection on stainless steel (STS) surface, where the rotation angle resolution reaches 0.1°. MT3502 is mainly used in smart devices, such as smart watches, smart bands, smart glasses, etc., for crown rotation and key press detection.

• First product in the industry featuring rotation and key detections

• Miniature OLGA package (3.5mm*3.2mm*0.65mm) with internal 850nm VCSEL

• 24*24 pixels super large sensing area, ultra-wide DoF range, and 0.5mm~30mm sensing height

• Up to 5000 CPI (STS surface) and supports 900rpm crown rotation speed

• Ultra-low power dissipation: 550μA@operating mode, 5μA@sleep mode, 1.5μA@standby mode

• Integrates OTP, CPI calibration with 0.625% accuracy

• Supports I²C with 1MHz speed and SDA/SCL swap to load two devices onto a pair of buses 

• Supports 2-wire SPI

• Features I/O key interrupt detection

• Designed with VCSEL fault detection function




MT3502 Typical Application Circuit

■  A highly integrated transceive

MT3502 adopts OLGA package and CIS process, integrates 850nm VCSEL, supports 24*24 pixels sensing area and up to 0.1° rotation angle resolution. Due to the large sensing area, the chip can receive signals from different reflection positions to widen the DoF, where the sensing height is low to 0.5mm, making it conductive to module miniature.

MT3502 light tracking diagram

■ High accuracy and low power dissipation

Based on the high-density pixel array, MT3502 is capable of realizing movement detection with the resolution of 5000 CPI (on STS surface) and 3200 counts/rev (1.0mm diameter STS shaft at 1.0mm distance). With a leading SNR level, integrated gain adaptive and crosstalk cancellation techniques, the chip can dynamically adapt to environmental interference to restore authentic signals.

MT3502 supports up to 5000fps frame frequency which is self-adaptive to the actual moving speed/shaft rotation speed of object, achieving dynamic balance between performance and power consumption. In addition, MT3502 features 3-level programmable sleep modes, by configuring the sleep cycle and waiting time, the switching between operating time and sleeping time is more stable and reliable.

MT3502 Flexible Configuration of Sleep Modes

MT3502 incorporates programmable OTP modules that retain data when powered down to store the factory-calibrated CPI separately, the parameter can be loaded automatically after powered on without occupying the storage space of MCU, realizing adaptive axis assembly tolerance calibration.

MT3502 features a key detection function that supports key signal input, when applied in digital crown applications, necessary bus between the crown module and MCU can be saved. At the same time, the chip supports I²C (default) and SPI for different scenarios, where the I²C interface supports 1MHz communication rate and SDA/SCL swap. Four MT3502 can be loaded onto a pair of buses simultaneously by configuring the address or swapping the I²C slave address, providing more options for innovative application combinations.

Independent Key Detection Function