3D imaging becomes the hottest topic in recent years thanks to the rising 3D visual applications and Face ID. Early digital cameras produce only 2D color images with any depth perception, meaning that we only know how wide and tall a building is in when we look at a picture, but have no idea of the 3-dimensional layout of the building, such as how large or deep the balcony is. The 3D imaging technology that gets people talking is the time of flight, or ToF. ToF sensors are widely used in AR, VR, cell phone face recognition, obstacle-evading / anti-collision system in drones and even in advanced driver assistance systems that keep drivers from loss of focus or distraction.
Technically, there are two groups of ToF sensors, dToF and iToF. First, dToF (direct ToF) works by emitting IR from LEDs or laser diodes (LDs) and calculating the distance from the object to be measured to the emitter based on the time difference after the beam reflects from the surface of object to be measured, as shown in Figure 1. The dToF seems very straightforward, but it was developed relatively later in time, as the requirements are rigorous for this technology in terms of light source and temporal testing circuits. This technology was first seen in 2020 in the LiDAR used in iPad Pro, as well as in iPhone 12 Pro and iPhone 12 Pro Max. The other is the iToF, or indirect ToF, which works by shooting light waves modulated to sine wave signals of a certain frequency onto the surface of an object, where the reflected lights are picked up by an iToF transceiver. In this way the depth is determined based on the difference in signals. For example, this technology was first seen in 2018 when it was adopted in cell phones such as VIVO NEX Dual Display and Huawei Honor V20. However, products like ToF sensors are susceptible to electrostatic discharge (ESD) from human body or electrical over-stress (EOS) at the charging end. It could lead to electronic system failure or even product damage that requires return for service. In some serious cases, the brand image is compromised as the general consumers lose their confidence.
Figure 1 Illustration of dToF sensing technology principle
Today, people want the chips used in their ToF sensors to be as small as possible and manufactured with a process as advanced as possible. The result is that products become increasingly sensitive and vulnerable to ESD and, therefore, ESD tests become more and more rigorous. One of the basic criteria is to pass the 8kV contact discharge test specified in IEC61000-4-2. This test simulates a system that is subject to electrostatic discharge when it is used by a user. Good protection is in place in advance to prevent large loss of costs as products are damaged or crashed due to ESD, as long as appropriate ESD/EOS protection elements are added to the design and signal wiring where it is sensitive.
At Amazing, we have cutting-edge ESD protection design technology. In particular for ToF sensor protection, a series of minimum-packaged ESD protection elements at multiple specifications are developed for customers to choose from based on their specific needs. Amazing launches a series of ESD protection elements based on proprietary technology and minimum package or 0402 or even 0201 is available for various applications. A single ESD element is capable of withstanding contact / air 8kV/15kV or more, and some of the elements are provided with EOS protection, as shown in Figure 2. The 0201 package is as small as 0.6 mm x 0.3mm and only 0.3 mm, enough to satisfy the need of ToF sensors for small package. As new technology develops, Amazing will continue to develop ESD protection elements that are much closer to what the market and customers need, and steer toward providing the perfect solutions for customized products.
Figure 2 Amazing’s TVSs in ToF application