What power semiconductor components are required for NFC payment device?
Preface
With the advent of the digital society, code scanning payment has become the habit of most people, but it still has the problem of cumbersome operation and dependence on the network. In order to make travel easier, simple operation and offline availability, touch to touch payment has returned. As of April 24, Alipay announced that the number of "touch to touch" users had exceeded 100 million. Simply put, Touch Pay is a contactless payment method based on NFC (Near Field Communication) technology, which has the characteristics of ease, security, and speed. NFC technology has promoted the growth of convenient pairing, diagnostic reading, data tracking, and other applications in consumer, industrial, automotive, and medical fields. This article will explain the principle of NFC technology and the discrete devices required.
The principle of NFC
The working principle of NFC is based on radio frequency identification (RFID) technology. Unlike traditional RFID, NFC has the characteristics of short distance communication and bidirectional communication. The working principle of NFC can be summarized in simple terms of "transmission and reception". Specifically, NFC devices communicate with each other through electromagnetic fields. When two NFC enabled devices are close enough, they exchange information through electromagnetic waves. NFC devices typically consist of a transmitter and a receiver.
In active mode, NFC devices actively send signals to communicate with other devices. Mobile phones or other devices will transmit signals through NFC chips and wait for the receiver's response; In passive mode, NFC devices do not actively send signals, but instead use electromagnetic fields from other devices to power and respond to signals. Passive mode is commonly used for devices such as cards and tags. For bidirectional mode, two NFC devices can send and receive information to each other. This mode is commonly used for pairing or file transfer between devices.
Composition of NFC
The external circuit of NFC chips usually consists of the following parts: power supply circuit, communication interface circuit, antenna circuit, and oscillation circuit. The multifunctional application of NFC cannot be achieved without the support of some core passive components in NFC circuits. In NFC circuits, the main components used are NFC antennas, magnetic films, inductors for LC filters, baluns, and double-layer capacitors (supercapacitors). The main focus here is on the important role played by passive component filters, inductors, and supercapacitors in NFC circuits.
Conclusion
NFC communication operates through electromagnetic induction, so circular antennas are generally used. Insert an LC filter consisting of antenna matching circuit, inductor, and capacitor between the antenna and NFC controller IC. For inductors used in short-range wireless applications, a narrower tolerance is required to reduce the losses caused by impedance mismatch between the inductor and the antenna. A tolerance of ± 5% is currently recognized as a narrow tolerance range. On the other hand, in order to prevent a decrease in antenna output, it is equally important to reduce the loss of inductors at the communication frequency of 13.56MHz. For this reason, the communication resistor also needs to be suppressed as low as possible in both situations of no current passing through and current passing through, so that the inductor can be more stable. Hottech 0402/0603 packaged capacitors achieve high-density mounting in a limited space, assisting in the lightweight design of terminal devices.