Double-layer NFC (Near Field Communication) touchpad

Abstract

The utility model discloses a double-layer NFC touch panel, and relates to the technical field of electrostatic protection of electronic products. The NFC touch screen comprises a touch control chip, an NFC chip and a power supply isolation circuit which are arranged on a second layer, the touch control chip and the NFC chip are connected through a connector, and the power supply isolation circuit is connected with the touch control chip, the NFC chip and the connector. Further, a first electrostatic protection circuit is arranged between the connector and the NFC chip, and a second electrostatic protection circuit is arranged between the touch control chip and the connector. According to the utility model, the static performance of the double-sided NFC touch panel can be effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of electrostatic protection of electronic products, in particular to a double-layer NFC touch panel. Background Art

[0002] Most of the existing touch panels with NFC functions adopt a four-layer PCB design. Among them, the first layer is the touch sensing electrode block (sensing channel pattern), the second layer is the touch driving electrode block (driving channel pattern), the third layer is the grid copper grounding design, and the fourth layer is used to lay out the touch channel routing, place components and design the NFC antenna, etc. The touch chip U1 and the NFC chip U2 are both controlled as slave devices by the PC main control chip through an I2C bus. The interrupt pins of the NFC and touch chip U1 are respectively connected to the PC main control end, and the two chips also share the same 3.3V power supply.

[0003] Because the four-layer board design is adopted, the third layer has a complete ground layer, and the touch driving signal and the sensing signal are also on different layers, so there are few touch channels that need to be connected through vias. Therefore, the electrostatic performance of the NFC touch panel with a four-layer board does not need to be specially processed. Directly connecting the functional pins on the chip end to the pins of the connector J1 can meet the electrostatic test requirements of the touch panel. At most, a TVS tube is reserved for the power supply, I2C, and IO port of the connector J1, and the increase or decrease depends on the electrostatic test effect. Although the touch panel with NFC function adopts a simple four-layer board design and good electrostatic performance, the cost is nearly twice that of the two-layer board. Therefore, in order to reduce the cost, it is necessary to study the two-layer board design of the NFC touch panel.

[0004] Since the front of the touchpad needs to be designed with a touch sensor pattern to detect finger touch, for the NFC touchpad of the double-layer PCB board, only one layer is left to place components and complete all touch and NFC routing, as well as the design of the NFC antenna. Without the ground layer of the original four-layer board design, the number of via routing connecting the touch channel will also increase a lot, which will cause the ground line of the entire touchpad to be incomplete, seriously affecting the electrostatic performance of the touchpad.

[0005] Furthermore, a new circuit design method is needed to improve the electrostatic performance of the double-layer NFC touch panel. Utility Model Content

[0006] The purpose of the utility model is to connect a double-layer NFC touch panel to solve the above technical problems existing in the prior art. The preferred technical solution among the many technical solutions connected by the utility model can produce many technical effects as described below.

[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] The utility model provides a double-layer NFC touch panel, including a touch chip U1, an NFC chip U2 and a power isolation circuit arranged on the second layer, wherein the touch chip U1 and the NFC chip U2 are connected via a connector J1, and the power isolation circuit is connected to the touch chip U1, the NFC chip U2 and the connector J1;

[0009] A first electrostatic protection circuit is provided between the connector J1 and the NFC chip U2 , and a second electrostatic protection circuit is provided between the touch chip U1 and the connector J1 .

[0010] Preferably, the power isolation circuit uses magnetic beads or resistors to separate the power terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2.

[0011] Preferably, the power isolation circuit includes a first magnetic bead LB1, a second magnetic bead LB2, a third magnetic bead LB3, a fourth magnetic bead LB4 and a capacitor C8;

[0012] One end of the first magnetic bead LB1 is provided with a connection terminal VDD-TP for connecting the touch control chip U1 to a power source, one end of the second magnetic bead LB2 is provided with a connection terminal VDD-NFC for connecting the NFC chip U2 to a power source, and a connection terminal VDD connected to the power source end of the connector J1 is provided between the first magnetic bead LB1 and the second magnetic bead LB2;

[0013] One end of the third magnetic bead LB3 is provided with the ground terminal GND-TP of the touch chip U1, one end of the fourth magnetic bead LB4 is provided with the ground terminal GND-NFC of the NFC chip U2, and a ground terminal GND is provided between the third magnetic bead LB3 and the fourth magnetic bead LB4;

[0014] One end of the capacitor C8 is connected between the first magnetic bead LB1 and the second magnetic bead LB2 , and the other end of the capacitor C8 is connected between the third magnetic bead LB3 and the fourth magnetic bead LB4 .

[0015] Preferably, the impedance frequency range of the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 is 50 MHz to 500 MHz, and the impedance resistance value range is 800Ω to 1.8 kΩ.

[0016] Preferably, the impedance resistance value of the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 is 1.5KΩ, and the impedance frequency is 100 MHz.

[0017] Preferably, when the power isolation circuit uses a resistor to separate the power terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2, the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 of the power isolation circuit are replaced by resistors respectively.

[0018] Preferably, the NFC chip U2 is connected to the connector J1 through a plurality of wires, and the first electrostatic protection circuit includes a plurality of first resistors and a plurality of TVS tubes arranged on the plurality of wires;

[0019] Two of the first resistors are connected in series on each wiring line, one end of a TVS tube is connected between the two first resistors, and the other end of the TVS tube is grounded.

[0020] Preferably, on each routing line, the resistance value of the first resistor close to the NFC chip U2 end is greater than the resistance value of the first resistor close to the connector J1 end.

[0021] Preferably, the second electrostatic protection circuit includes a plurality of second resistors, and each I2C port and each IO port of the touch control chip U1 is connected in series with a second resistor.

[0022] Preferably, the double-layer NFC touch panel further includes driving electrodes and sensing electrodes arranged on the first layer, the driving electrodes are connected to the touch chip U1 through driving channels, and the sensing electrodes are connected to the touch chip U1 through sensing channels.

[0023] Implementing one of the above technical solutions of the utility model has the following advantages or beneficial effects:

[0024] The utility model separates the power supply, ground, I2C, and IO that are commonly connected to the NFC chip and the touch chip with related circuits, and adds TVS tubes to their respective lines to reduce the impact of electrostatic energy. In addition, resistors or magnetic beads are connected in series at both ends of the long NFC line that is easy to absorb electrostatic energy, so as to minimize the electrostatic energy absorbed by the NFC line and transferred to the touch chip, thereby improving the antistatic performance of the double-sided NFC touch panel. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0026] Figure 1This is a schematic diagram of the electrostatic protection circuit of the touch chip of the double-layer NFC touch panel of the utility model;

[0027] Figure 2 This is a schematic diagram of the connector circuit of the double-layer NFC touch panel of the utility model;

[0028] Figure 3 This is a schematic diagram of the power isolation circuit of the double-layer NFC touch panel of the utility model;

[0029] Figure 4 This is a schematic diagram of the NFC chip electrostatic protection circuit of the double-layer NFC touch panel of the utility model;

[0030] Figure 5 The layout diagram of the double-layer NFC touch panel of the utility model. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the utility model clearer, the various exemplary embodiments to be described below will refer to the corresponding drawings, which constitute a part of the exemplary embodiments, wherein various exemplary embodiments that may be used to implement the utility model are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation methods described in the following exemplary embodiments do not represent all implementation methods consistent with the present disclosure. It should be understood that they are only examples of processes, methods, and devices that are consistent with some aspects of the utility model disclosed as detailed in the attached claims, and other embodiments may also be used, or the embodiments listed herein may be modified in structure and function without departing from the scope and essence of the utility model.

[0032] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", etc. indicate the orientation or position relationship based on the drawings, which is only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation. The terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "multiple" means two or more. The terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a communication connection, a direct connection, an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to the specific circumstances.

[0033] In order to illustrate the technical solution of the present invention, a specific embodiment is provided below, in which only the parts related to the embodiment of the present invention are shown.

[0034] like Figure 1-Figure 4 As shown, the utility model is a double-layer NFC touch panel, including a touch chip U1, an NFC chip U2 and a power isolation circuit arranged on the second layer, the touch chip U1 and the NFC chip U2 are connected through a connector J1, and the power isolation circuit is connected to the touch chip U1, the NFC chip U2 and the connector J1. Furthermore, a first electrostatic protection circuit is arranged between the connector J1 and the NFC chip U2, and a second electrostatic protection circuit is arranged between the touch chip U1 and the connector J1.

[0035] Through the test and analysis of the electrostatic performance of the double-layer NFC touch panel, it is found that the main reason is that the circuit of the NFC chip (especially the NFC antenna) transmits the absorbed electrostatic energy to the touch chip through the I2C bus, power supply, IO port and other signal lines connected to the touch chip, which causes the touch chip to have soft failure and other problems due to the excessive electrostatic energy entering. The four-layer NFC touch panel has a complete ground layer with low ground impedance, so the electrostatic energy absorbed by the NFC circuit can be easily discharged from the ground layer through the connector pins.

[0036] In view of the above characteristics, this double-layer NFC touch panel adjusts the anti-static circuits of the touch chip and NFC chip respectively, separates the power supply, ground, I2C, and IO related circuits that are commonly connected to the NFC chip and the touch chip, and adds TVS tubes to their respective lines to reduce the impact of electrostatic energy. In addition, resistors or magnetic beads are connected in series at both ends of the long NFC lines that are easy to absorb electrostatic energy, so as to minimize the transfer of electrostatic energy absorbed by the NFC line to the touch chip, thereby improving the anti-static performance of the double-sided NFC touch panel.

[0037] like Figure 2 As shown, the connector J1 is provided with an SDA terminal and an SCL terminal connected to the power supply terminal VDD, the I2C port of the touch chip U1 (pin 29 and pin 30 of the touch chip U1) and the I2C port of the NFC chip U2 (pin 8 and pin 7 of the NFC chip U2), an INT terminal connected to pin 26 of the touch chip U1, an NFC-INT terminal connected to pin 10 of the NFC chip U2, and a PEPORT-EN terminal connected to pin 33 of the touch chip U1. The terminals are grounded through TVS tubes, respectively, as shown in FIG. Figure 2 TVS1, TVS2, TVS3, TVS4, TVS5, and TVS6.

[0038] As an implementation mode, the power isolation circuit uses magnetic beads or resistors to separate the power supply terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2. Specifically, when the power isolation circuit uses magnetic beads to separate the power supply terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2, the power isolation circuit includes a first magnetic bead LB1, a second magnetic bead LB2, a third magnetic bead LB3, a fourth magnetic bead LB4, and a capacitor C8.

[0039] like Figure 3 As shown, one end of the first magnetic bead LB1 is provided with a connection terminal VDD-TP for connecting the touch chip U1 to a power supply, one end of the second magnetic bead LB2 is provided with a connection terminal VDD-NFC for connecting the NFC chip U2 to a power supply, and a connection terminal VDD connected to the power supply end of the connector J1 is provided between the first magnetic bead LB1 and the second magnetic bead LB2; one end of the third magnetic bead LB3 is provided with a ground terminal GND-TP of the touch chip U1, one end of the fourth magnetic bead LB4 is provided with a ground terminal GND-NFC of the NFC chip U2, and a ground terminal GND is provided between the third magnetic bead LB3 and the fourth magnetic bead LB4; one end of the capacitor C8 is connected between the first magnetic bead LB1 and the second magnetic bead LB2, and the other end is connected between the third magnetic bead LB3 and the fourth magnetic bead LB4.

[0040] As an implementation manner, the impedance frequency range of the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 is: 50MHz~500MHz, and the impedance resistance value range is: 800Ω~1.8kΩ.

[0041] Preferably, the impedance frequency of the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 is 100 MHz, and the impedance resistance value is 1.5 KΩ.

[0042] It should be noted that the magnetic bead model uses a higher impedance of 1.5KΩ (impedance resistance value) @100MHz (impedance frequency). Because the static energy on the NFC touch panel is mainly distributed in the frequency range of 50MHz to 500MHz, high-impedance magnetic beads can better reduce static energy and transmit static energy from the power supply and ground wires into the touch chip.

[0043] Preferably, the model of the touch chip U1 is: RX28 / TX18, and the model of the NFC chip U2 is: FM11NT082CI.

[0044] As an implementation method, when the power isolation circuit uses magnetic beads to separate the power terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2, the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 of the power isolation circuit are replaced with resistors respectively. That is, the connection relationship remains unchanged, and only the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 are replaced with corresponding resistors.

[0045] As an implementation method, the NFC chip U2 is connected to the connector J1 through multiple wires, and the first electrostatic protection circuit includes multiple first resistors and multiple TVS tubes arranged on the multiple wires. Specifically, two first resistors are connected in series on each wire, one end of a TVS tube is connected between the two first resistors, and the other end of a TVS tube is grounded.

[0046] like Figure 4 As shown, as an example, the NFC chip U2 is connected to the connector J1 through three traces, the trace corresponding to the NFC-INT port (which may be referred to as the INT trace), the trace corresponding to the SDA port (which may be referred to as the SDA trace), and the trace corresponding to the SCL port (which may be referred to as the SCL trace). Specifically, two first resistors, such as resistor R16 and resistor R23, are connected in series on the routing corresponding to the NFC-INT port, a TVS tube T14 is connected between the resistor R16 and the resistor R23, one end of the TVS tube T14 is connected between the resistor R16 and the resistor R23, and the other end is grounded; two first resistors, such as resistor R17 and resistor R20, are connected in series on the routing corresponding to the SDA port, a TVS tube T12 is connected between the resistor R17 and the resistor R20, one end of the TVS tube T12 is connected between the resistor R17 and the resistor R20, and the other end is grounded; two first resistors, such as resistor R19 and resistor R21, are connected in series on the routing corresponding to the SCL port, a TVS tube T13 is connected between the resistor R19 and the resistor R21, one end of the TVS tube T13 is connected between the resistor R19 and the resistor R21, and the other end is grounded.

[0047] As an implementation mode, on each line, the resistance value of the first resistor near the NFC chip U2 end is greater than the resistance value of the first resistor near the connector J1 end. Preferably, on each line, the resistance value of the first resistor near the NFC chip U2 end is twice the resistance value of the first resistor near the connector J1 end. As in the above embodiment, the resistance values ​​of multiple first resistors near the connector J1 end, such as resistor R23, resistor 20, and resistor 21, are all 10Ω, and the resistance values ​​of multiple first resistors near the NFC chip U2 end, such as resistor R16, resistor R17, and resistor R19, are all 20Ω.

[0048] It should be noted that the other end of the connector is connected to a high-impedance ferrite bead and TVS. The resistance near the connector end is smaller than that near the NFC chip end. Its function is to serve as a residual pressure path for releasing electrostatic energy and reduce the voltage at the chip end, so that two levels of electrostatic protection are formed at both ends of the connector and the NFC chip.

[0049] As an implementation manner, the second electrostatic protection circuit includes a plurality of second resistors, and each I2C port and each IO port of the touch control chip U1 is connected in series with a second resistor.

[0050] like Figure 1 As shown, as an example, the I2C port includes an SDA port (corresponding to pin 29 on the touch chip U1), an SCL port (corresponding to pin 30 on the touch chip U1), and the IO port includes a PEPORT-INT port (corresponding to pin 33 on the touch chip U1), an NFC-INT port (corresponding to pin 32 on the touch chip U1), a KEY port (corresponding to pin 27 on the touch chip U1), and an INT port (corresponding to pin 26 on the touch chip U1). A plurality of second resistors are connected in series to the PEPORT-INT port, the NFC-INT port, the SCL port, the SDA port, the KEY port, and the INT port, such as resistor R6, resistor R4, resistor R5, resistor R3, resistor R7, and resistor R8. Further, the resistance values ​​of resistors R6, resistor R4, resistor R5, resistor R3, resistor R7, and resistor R8 are preferably 100Ω.

[0051] The double-layer NFC touch panel of this embodiment further includes driving electrodes and sensing electrodes arranged on the first layer, the driving electrodes are connected to the touch chip U1 through driving channels, and the sensing electrodes are connected to the touch chip U1 through sensing channels. Specifically, the first layer is provided with 27 driving electrodes and 17 sensing electrode blocks. Figure 1 In the embodiment, the RX0-RX27 pins on the touch chip are used to connect the sensing channels of the sensing electrodes, and the TX0-TX17 pins on the touch chip are used to connect the driving channels of the driving electrodes.

[0052] like Figure 5As shown, there are two component areas of the touch panel with NFC function, distributed on the left and right sides of the touch panel, one for the connector and the touch chip, and the other for the NFC chip. The NFC component area is generally far away from the connector. Therefore, the three lines corresponding to the SDA port, SCL port, and NFC_INT port of the NFC chip are relatively long, and therefore are also greatly affected by static electricity. In this embodiment, two resistors and a TVS tube are designed for each line, a resistor with a larger resistance value is connected in series near the NFC chip end, and a resistor with a smaller resistance value is connected in series near the connector end, and a TVS tube is designed between the two resistors, near the connector side, to reduce the electrostatic energy. Therefore, this minimizes the electrostatic energy absorbed by the NFC line and transferred to the touch chip, effectively improving the antistatic performance of the double-sided NFC touch panel.

[0053] The above description is only the preferred embodiment of the present invention. Those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the guidance of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the protection scope of the present invention.

Claims

1. A double-layer NFC touch panel, characterized in that: It includes a touch chip U1, an NFC chip U2 and a power isolation circuit arranged on the second layer, wherein the touch chip U1 and the NFC chip U2 are connected via a connector J1, and the power isolation circuit is connected to the touch chip U1, the NFC chip U2 and the connector J1; A first electrostatic protection circuit is provided between the connector J1 and the NFC chip U2 , and a second electrostatic protection circuit is provided between the touch chip U1 and the connector J1 .

2. A double-layer NFC touch panel according to claim 1, characterized in that: The power isolation circuit uses magnetic beads or resistors to separate the power terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2.

3. A double-layer NFC touch panel according to claim 2, characterized in that: The power isolation circuit includes a first magnetic bead LB1, a second magnetic bead LB2, a third magnetic bead LB3, a fourth magnetic bead LB4 and a capacitor C8; One end of the first magnetic bead LB1 is provided with a connection terminal VDD-TP for connecting the touch control chip U1 to a power source, one end of the second magnetic bead LB2 is provided with a connection terminal VDD-NFC for connecting the NFC chip U2 to a power source, and a connection terminal VDD connected to the power source end of the connector J1 is provided between the first magnetic bead LB1 and the second magnetic bead LB2; One end of the third magnetic bead LB3 is provided with the ground terminal GND-TP of the touch chip U1, one end of the fourth magnetic bead LB4 is provided with the ground terminal GND-NFC of the NFC chip U2, and a ground terminal GND is provided between the third magnetic bead LB3 and the fourth magnetic bead LB4; One end of the capacitor C8 is connected between the first magnetic bead LB1 and the second magnetic bead LB2 , and the other end of the capacitor C8 is connected between the third magnetic bead LB3 and the fourth magnetic bead LB4 .

4. A double-layer NFC touch panel according to claim 3, characterized in that: The impedance frequency range of the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 is 50 MHz to 500 MHz, and the impedance resistance value range is 800Ω to 1.8 kΩ.

5. A double-layer NFC touch panel according to claim 4, characterized in that: The impedance resistance value of the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 is 1.5KΩ, and the impedance frequency is 100 MHz.

6. A double-layer NFC touch panel according to claim 3, characterized in that: When the power isolation circuit uses resistors to separate the power terminal and the ground terminal on the connector J1 into independent power supply circuits for the touch chip U1 and the NFC chip U2, the first magnetic bead LB1, the second magnetic bead LB2, the third magnetic bead LB3, and the fourth magnetic bead LB4 of the power isolation circuit are replaced by resistors respectively.

7. A double-layer NFC touch panel according to claim 1, characterized in that: The NFC chip U2 is connected to the connector J1 through a plurality of wires, and the first electrostatic protection circuit includes a plurality of first resistors and a plurality of TVS tubes arranged on the plurality of wires; Two of the first resistors are connected in series on each wiring line, one end of a TVS tube is connected between the two first resistors, and the other end of the TVS tube is grounded.

8. A double-layer NFC touch panel according to claim 7, characterized in that: On each trace, the resistance value of the first resistor close to the NFC chip U2 end is greater than the resistance value of the first resistor close to the connector J1 end.

9. A double-layer NFC touch panel according to claim 1, characterized in that: The second electrostatic protection circuit includes a plurality of second resistors, and each I2C port and each IO port of the touch control chip U1 are connected in series with a second resistor.

10. A double-layer NFC touch panel according to claim 1, characterized in that: It also includes driving electrodes and sensing electrodes arranged on the first layer, wherein the driving electrodes are connected to the touch chip U1 through driving channels, and the sensing electrodes are connected to the touch chip U1 through sensing channels.

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