A radio frequency port electrostatic protection circuit, radio frequency chip and radio frequency device

Abstract

The present application provides a radio frequency port electrostatic protection circuit, a radio frequency chip and a radio frequency device, the circuit comprising: n transistors cascaded in sequence, the gates of each transistor being connected to a negative power supply through a first resistor; a second resistor being connected in parallel between the source and drain of the first n-1-stage transistors, the drain of the first-stage transistor being connected to the radio frequency port; a capacitor being connected in parallel between the source and drain of the last-stage transistor, and the source of the last-stage transistor being grounded, wherein n is a positive integer. Compared with the circuit of the traditional diode series structure, the present application has fewer stages of cascade devices, lower on-resistance, and can achieve a higher level of electrostatic protection.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency technology applications, and in particular to a radio frequency port electrostatic protection circuit, a radio frequency chip and a radio frequency device. Background Art

[0002] Chips will accumulate charges during production, storage, transportation and use. When these static charges are discharged through the ports of the chip, they may cause damage to the internal devices of the chip. Therefore, it is necessary to design electrostatic protection circuits on the ports inside the chip to prevent damage to the internal devices of the chip during static discharge.

[0003] For RF chips, since the RF ports need to be connected to antennas or other chips, the RF ports of RF chips are more susceptible to damage from static electricity. However, the turn-on voltage and on-resistance of existing electrostatic protection circuits are relatively large, making it difficult to meet high-level electrostatic discharge requirements. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present application proposes a radio frequency port electrostatic protection circuit, a radio frequency chip and a radio frequency device, which mainly solve the problem that the existing electrostatic protection circuit is difficult to meet the high-level electrostatic protection requirements.

[0005] In order to achieve the above-mentioned purpose and other purposes, the technical solution adopted in this application is as follows.

[0006] The present application provides a radio frequency port electrostatic protection circuit, which includes: n transistors cascaded in sequence, the gates of each transistor being connected to a negative power supply through a first resistor; a second resistor being connected in parallel between the source and drain of the first n-1 stages of transistors, and the drain of the first stage of transistors being connected to the radio frequency port; a capacitor being connected in parallel between the source and drain of the last stage of transistors, and the source of the last stage of transistors being grounded, wherein n is a positive integer.

[0007] In an embodiment of the present application, the transistor includes an NMOS transistor.

[0008] In one embodiment of the present application, the minimum number of cascaded transistors in the circuit is determined by the RF port power, the negative power supply voltage, and the threshold voltage of the transistor.

[0009] The present application also provides a radio frequency chip, characterized in that it comprises the radio frequency port electrostatic protection circuit described in any one of claims 1-3.

[0010] The present application also provides a radio frequency device, including a radio frequency chip and the radio frequency port electrostatic protection circuit, wherein the radio frequency port electrostatic protection circuit is connected to the radio frequency port of the radio frequency chip to discharge static electricity of the radio frequency port.

[0011] As described above, the RF port electrostatic protection circuit, RF chip and RF device proposed in the present application have the following beneficial effects.

[0012] The present application cascades multiple transistors. Compared with the traditional diode series circuit, the number of cascade devices is fewer and the on-resistance is lower, so a higher level of electrostatic protection can be achieved; the transistor gate is connected to the negative power supply through a first resistor, and the radio frequency signal can be isolated from the negative power supply through the first resistor to prevent the radio frequency signal from leaking to the negative power supply; in addition, providing a negative voltage through the negative power supply can improve the linearity index of the electrostatic protection circuit and reduce the parasitic capacitance of the transistor; a second resistor is connected in parallel between the source and drain of each stage of the transistor, so that the DC voltage of the source and drain of each transistor can be kept consistent with the radio frequency port, and the radio frequency voltage can be evenly distributed on the corresponding transistor; the capacitor is connected in parallel at the last stage to isolate the DC voltage of the radio frequency port from the ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of an existing electrostatic protection circuit.

[0014] Figure 2 Schematic diagram of the circuit structure of the radio frequency port electrostatic protection circuit in one embodiment of the present application. DETAILED DESCRIPTION

[0015] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0016] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0017] The inventors have found that:

[0018] See also Figure 1 , Figure 1The figure is a schematic diagram of the structure of an existing electrostatic protection circuit. Conventional RF port electrostatic protection circuits usually adopt a series diode structure, which is composed of a string of forward diodes to ground and a string of reverse diodes to ground. The RF port of the RF chip often has a DC working voltage, so more forward diodes need to be connected in series to prevent the forward diode from being turned on. At the same time, there is also an RF signal at the RF port. In order to prevent the series diode from being turned on due to the RF signal voltage, multiple diodes need to be connected in series in both the forward and reverse directions to the ground. The greater the power of the RF port, the more series diodes there are, the greater the turn-on voltage and on-resistance of the electrostatic protection circuit, and it is difficult to achieve electrostatic discharge. Therefore, it is difficult for the RF port of the electrostatic protection circuit with a conventional series diode structure to achieve a high level of electrostatic protection capability.

[0019] Specifically, the conventional radio frequency port electrostatic protection circuit is composed of forward cascade diodes D1 to D n-1 And reverse cascade diodes DB1~DB m-1 Composition. Diodes D1~D n-1 There are n stages in the forward direction from the RF port to the ground, and the conduction voltage is n V (the voltage of the diode when it is fully turned on is about 1 V, and the conduction voltage of n stages in series is n V). m-1 It is reversely cascaded from the RF port to the ground, with a total of m stages, and its conduction voltage is -m V (the voltage of the reverse diode fully turned on is about -1V, and the conduction voltage of the m-stage series connection is -m V). Its working principle is: when there is a positive electrostatic voltage at the RF port and it is higher than n V, the forward diode string to the ground is turned on to discharge static electricity; when there is a negative electrostatic voltage at the RF port and it is lower than -m V, the reverse diode string to the ground is turned on to discharge static electricity.

[0020] Under 50Ω characteristic impedance, when the signal power of the RF port is P and the DC working voltage of the RF port is 0V, in order to ensure that the series diode will not be turned on due to the signal voltage, the minimum number of forward and reverse series diodes is: When the RF port power is 1W, the minimum number of forward and reverse series diodes is 10. When the RF port has a DC working voltage, in order to prevent the forward diode from conducting, the number of forward diodes n will be larger. The more diodes are connected in series, the greater the on-resistance and the weaker the electrostatic discharge capability. Therefore, it is difficult for the conventional diode structure RF port electrostatic protection circuit to achieve a high level of electrostatic protection capability.

[0021] Based on the problems existing in the prior art, the present application proposes a radio frequency port electrostatic protection circuit, a radio frequency chip and a radio frequency device. The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0022] See also Figure 2 , Figure 2The schematic diagram of the circuit structure of the radio frequency port electrostatic protection circuit in an embodiment of the present application. The radio frequency port electrostatic protection circuit provided in the embodiment of the present application comprises: n transistors cascaded in sequence, the gate of each transistor is connected to a negative power supply through a first resistor; a second resistor is connected in parallel between the source and drain of the first n-1 stages of transistors, and the drain of the first stage of transistors is connected to the radio frequency port; a capacitor is connected in parallel between the source and drain of the last stage of transistors, and the source of the last stage of transistors is grounded, wherein n is a positive integer.

[0023] In one embodiment, the transistor may be an NMOS tube, and the RF port electrostatic protection circuit is composed of an NMOS tube, a first resistor, a second resistor, and a capacitor. The second resistor RB1 is connected to the source and drain of the NMOS tube M1, one end of the first resistor RG1 is connected to the gate of the NMOS tube M1, and the other end is connected to the negative power supply VSS. The network composed of the first resistor RG1, the NMOS tube M1, and the second RB1 is cascaded to n-1 levels. The nth level consists of the NMOS tube M n , the first resistor RG n and capacitor C n The first resistor RG n One end is connected to NMOS tube M n The other end is connected to the negative power supply VSS. n The drain of NMOS tube M n-1 The source and capacitor C n One end of NMOS tube M n The source and capacitor C n The other end of the capacitor is grounded. n The function of isolating the DC voltage of the RF port from the ground. n-1 It is a voltage divider resistor, which is used to make M1~M n-1 The DC voltage of the source and drain of the NMOS tube is consistent with the RF port, and the RF voltage is evenly distributed from M1 to M n-1 The first resistor RG1~RG n The function of the negative power supply VSS is to prevent the RF signal from leaking through the gate of the NMOS tube to the negative power supply VSS. n The gate-source voltage is a negative voltage, which can not only improve the linearity indicators such as the input 1dB compression point and the third-order intermodulation cutoff point of the electrostatic protection circuit, but also reduce the parasitic capacitance of the NMOS tube.

[0024] In one embodiment, the minimum number of cascaded transistors in the circuit is determined by the RF port power, the negative power supply voltage, and the threshold voltage of the transistor. Specifically, under a characteristic impedance of 50Ω, when the signal power of the RF port is P and the DC operating point of the RF port is 0V, in order to ensure that the NMOS tube is not turned on due to the signal voltage, the minimum number of cascaded NMOS tubes is: Where VSS is a negative voltage, V th is the threshold voltage of the NMOS tube. Assuming that the RF port power is 1W, the negative voltage VSS is -2V, and the NMOS tube threshold voltage V th is 0.5V, then the minimum number of cascaded NMOS tubes is 3, while the electrostatic protection circuit of the diode structure under the same power requires 10 diode cascades. Therefore, the RF port electrostatic protection circuit proposed in the embodiment of the present application has fewer cascaded device levels than the RF port electrostatic protection circuit of the conventional diode structure, and the on-resistance of the unit size NMOS tube is also less than the on-resistance of the diode. Therefore, the RF port electrostatic protection circuit proposed in the embodiment of the present application has a lower on-resistance under the same high signal power tolerance conditions, and can achieve a higher level of electrostatic protection capability. By appropriately increasing the number of cascaded NMOS tubes, high tolerance power and high electrostatic protection capability can be achieved at the same time.

[0025] In one embodiment, the present application further provides a radio frequency chip, which may include the radio frequency port electrostatic protection circuit in the aforementioned embodiment, and the specific circuit structure will not be repeated here.

[0026] In one embodiment, the present application also provides a radio frequency device, including a radio frequency chip and the radio frequency port electrostatic protection circuit, wherein the radio frequency port electrostatic protection circuit is connected to the radio frequency port of the radio frequency chip to discharge the static electricity of the radio frequency port. Of course, the radio frequency device may also include multiple radio frequency chips, and each radio frequency chip is connected to a corresponding radio frequency port electrostatic protection circuit. Exemplarily, the radio frequency ports of multiple radio frequency chips may also share a radio frequency port electrostatic protection circuit, which can be selected and set according to actual application requirements, and is not limited here.

[0027] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A radio frequency port electrostatic protection circuit, characterized in that: The circuit includes: n transistors cascaded in sequence, the gate of each transistor is connected to a negative power supply through a first resistor; a second resistor is connected in parallel between the source and drain of the first n-1 stages of transistors, and the drain of the first stage of transistors is connected to a radio frequency port; a capacitor is connected in parallel between the source and drain of the last stage of transistors, and the source of the last stage of transistors is grounded, wherein n is a positive integer.

2. The radio frequency port electrostatic protection circuit according to claim 1, characterized in that: The transistor includes an NMOS transistor.

3. The radio frequency port electrostatic protection circuit according to claim 1, characterized in that: The minimum number of cascaded transistors in the circuit is determined by the RF port power, the negative power supply voltage, and the threshold voltage of the transistors.

4. A radio frequency chip, characterized in that: It comprises the radio frequency port electrostatic protection circuit as described in any one of claims 1-3.

5. A radio frequency device, characterized in that: It comprises a radio frequency chip and the radio frequency port electrostatic protection circuit as described in any one of claims 1-3, wherein the radio frequency port electrostatic protection circuit is connected to the radio frequency port of the radio frequency chip to discharge the static electricity of the radio frequency port.

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