Input overvoltage protection circuit for radio frequency adc

Abstract

The application relates to radio frequency technology and particularly provides an input overvoltage protection circuit of a radio frequency ADC, which comprises an ADC acquisition unit; a switching unit is used for selectively making a voltage signal enter a first channel or a second channel, wherein an attenuation circuit is arranged in the second channel; the output ends of the first channel and the second channel are sequentially connected with a first radio frequency operational amplifier and the ADC acquisition unit, the first radio frequency operational amplifier completes single-end to differential conversion; and an identification circuit is connected with the output ends of the first channel and the second channel, and when it is identified that the voltage of the first channel exceeds a set value, the voltage signal selects the second channel. The application has the advantages of good protection effect and the like and can be applied in a mass spectrometer.

Description

TECHNICAL FIELD

[0001] The application relates to radio frequency technology, in particular to an input overvoltage protection circuit of a radio frequency ADC. BACKGROUND

[0002] The input overvoltage protection of the ADC is often realized by a built-in voltage stabilizing tube. Since the voltage stabilizing tube has a large capacitance, for a radio frequency signal of GHz, the capacitance is too large, which leads to distortion of the radio frequency input signal. Therefore, for the radio frequency ADC, the built-in voltage stabilizing tube mode is not feasible.

[0003] The input port overvoltage protection of the radio frequency ADC can only be externally protected according to the actual use of the user, and the principle is to increase the voltage range that the input port of the ADC can withstand under the condition of ensuring that the input signal is not distorted. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides an input overvoltage protection circuit of a radio frequency ADC.

[0005] The application aims to realize the following technical scheme:

[0006] The input overvoltage protection circuit of the radio frequency ADC comprises an ADC acquisition unit; the protection circuit further comprises:

[0007] A switching unit and an attenuation circuit, the switching unit is used for selectively entering a voltage signal into a first channel or a second channel, and the attenuation circuit is arranged in the second channel; the output ends of the first channel and the second channel are connected with a first radio frequency operational amplifier and the ADC acquisition unit in sequence, and the first radio frequency operational amplifier completes single-ended to differential conversion;

[0008] An identification circuit, the identification circuit is connected with the output ends of the first channel and the second channel, and when it is identified that the voltage of the first channel exceeds a set value, the voltage signal selects the second channel.

[0009] Compared with the prior art, the application has the beneficial effects that:

[0010] The radio frequency attenuation circuit is added in front of the radio frequency ADC, the attenuation circuit is controlled to realize timely attenuation of the overvoltage signal, since the attenuator is only a resistive switching device, the influence of the attenuator on signal distortion is much smaller than that of the ESD device;

[0011] The damage energy generated by the overvoltage of the input signal for a short time is not enough to damage the input port structure of the ADC, the core is to effectively and timely identify the signal that can damage the input structure of the ADC and attenuate it, and the overvoltage pulse with low energy (peak-to-peak value or short duration) is not attenuated, so as to improve the working efficiency of the ADC. BRIEF DESCRIPTION OF DRAWINGS

[0012] The disclosure of the present application will become more apparent from the following description in conjunction with the accompanying drawings. It is readily understood by those skilled in the art that the drawings are only for the purpose of illustration and are not intended to limit the scope of the present application. In the drawings:

[0013] Figure 1 is a structural schematic diagram of an input overvoltage protection circuit of a radio frequency ADC according to the present application;

[0014] Figure 2 is a structural schematic diagram of a recognition circuit according to the present application. DETAILED DESCRIPTION

[0015] Figures 1-2 The following description describes optional specific embodiments of the present application to teach those skilled in the art how to implement and reproduce the present application. Some conventional aspects have been simplified or omitted in order to teach the technical solutions of the present application. Those skilled in the art should understand that variations or substitutions derived from these specific embodiments will be within the scope of the present application. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present application. Thus, the present application is not limited to the following optional specific embodiments, but is only defined by the claims and their equivalents. EMBODIMENT

[0016] An input overvoltage protection circuit of a radio frequency ADC of the present embodiment is shown in Figure 1 The protection circuit includes:

[0017] The switching unit is used to selectively make the voltage signal enter the first channel or the second channel, and the attenuation circuit is arranged in the second channel and includes voltage dividing resistors R1 and R2; the output ends of the first channel and the second channel are connected in sequence with a first radio frequency operational amplifier U2 and the ADC acquisition unit U1, and the first radio frequency operational amplifier U2 completes single-ended to differential conversion.

[0018] The recognition circuit is connected to the output ends of the first channel and the second channel, and when it is recognized that the voltage of the first channel exceeds a set value, the voltage signal selects the second channel.

[0019] As shown in Figure 2 The switching unit includes a first switch Z1 arranged in the first channel and a second switch Z2 arranged upstream of the attenuation circuit in the second channel.

[0020] As shown in Figure 2 The recognition circuit includes:

[0021] The input end of a second radio frequency operational amplifier U3 is connected to the output end of the first radio frequency operational amplifier, and the output ends are respectively connected to a first comparator U4 and a third switch Z4.

[0022] The output of the first comparator U4 controls the third switch Z4.

[0023] The third switch Z4, the integration circuit and the second comparator U6 are connected in sequence, and the output of the second comparator U6 controls the first switch Z1 and the second switch Z2.

[0024] In order to release the accumulated charge, the identification circuit further comprises:

[0025] The first comparator U4, the first NOT gate A3, the fourth switch Z5 and the integration circuit are connected in sequence, and the fourth switch Z5 is grounded.

[0026] In order to control the switching unit, the identification circuit further comprises:

[0027] The output of the second comparator U6 is connected with the second NOT gate A2 and the third NOT gate A1 in sequence, the output of the second NOT gate A2 is connected with the first switch Z1, and the output of the third NOT gate A1 is connected with the second switch Z2.

[0028] The fifth switch Z3 is arranged downstream of the attenuation circuit on the second channel, and the output of the third NOT gate A1 is connected with the fifth switch Z3.

[0029] The above switches are all MOS tubes, which are cut off when the input is low and turned on when the input is high.

[0030] The working mode of the protection circuit of the embodiment is as follows:

[0031] The non-overvoltage signal RF_INPUT comes in, and under normal circumstances, it directly enters the first RF operational amplifier U2 through the first switch Z1 to complete single-ended to differential conversion, and then enters the ADC sampling unit. At the same time, the differential signal entering the ADC sampling unit U1 is converted into single-ended SIG3 through the second RF operational amplifier U3, and is output in two ways. One way is to enter the first comparator U4 for comparison with REF1. If the RF_INPUT is enhanced to make the differential to single-ended signal exceed REF1, at this time, the first comparator U4 outputs high level, and the third switch Z4 is opened. That is, the second way of signal SIG3 completes signal strength integration at the integration circuit U5, and SIG4= Only the continuous overvoltage signal input, will trigger this place continuous overvoltage signal integration, integration output SIG4 accumulation over REF2, will trigger the second comparator U6 output high level T2, high level T2 through the second NAND gate A2 inversion to low level T3, drive the first switch Z1 off, low level T3 through the third NAND gate A1 inversion to high level T4, drive the second switch Z2 and the fifth switch Z3 on, so that the radio frequency attenuation circuit resistance R1 and R2 can attenuate the input overvoltage signal, the attenuated signal drive SIG3 lower than REF1, the first comparator U4 output low level T1, drive the third switch Z4 off, low level TI through the first NAND gate A3 inversion to high level, drive the fourth switch Z5 quickly release SIG4 accumulated charge, for the next overvoltage integration to do good initialization.

[0032] Through the overvoltage signal in time attenuation to realize overvoltage protection, at the same time, avoid the traditional ESD protection device due to the parasitic capacitance and lead to signal distortion, effectively reduce the probability of ADC acquisition unit U1 input port is damaged by high voltage.

[0033] In order to increase the flexibility of overvoltage protection, REF1 voltage can be provided by software control DAC, according to the software analysis of the strength of the current input signal statistical information, give reasonable overvoltage protection threshold, thereby reducing the probability of false protection.

Claims

1. An input overvoltage protection circuit of a radio frequency ADC, comprising an ADC acquisition unit; characterized in that, The protection circuit further comprises: A switching unit for selectively entering a voltage signal into a first channel or a second channel, and an attenuation circuit arranged in the second channel; output ends of the first channel and the second channel are connected with a first RF operational amplifier and the ADC acquisition unit in sequence, and the first RF operational amplifier is used to complete single-ended to differential conversion; the switching unit comprises a first switch arranged in the first channel and a second switch arranged upstream of the attenuation circuit in the second channel; An identification circuit connected with output ends of the first channel and the second channel, which selects the second channel for the voltage signal when it is identified that the voltage of the first channel exceeds a set value; The identification circuit comprises: A second RF operational amplifier and a third switch, an input end of the second RF operational amplifier is connected with an output end of the first RF operational amplifier, and output ends of the second RF operational amplifier are respectively connected with an input end of a first comparator and a first end of the third switch; The first comparator, an output end of the first comparator is connected with a control end of the third switch, and another input end of the first comparator is connected with a signal REF1; An integration circuit and a second comparator, the integration circuit comprises an additional operational amplifier and a capacitor, a second end of the third switch is connected with a first input end of the additional operational amplifier, one end of the capacitor is connected with a second input end of the additional operational amplifier, and an output end of the additional operational amplifier is connected with an input end of the second comparator and another end of the capacitor, an output result of the second comparator controls the first switch and the second switch, and another input end of the second comparator is connected with a signal REF2; A first NOT gate and a fourth switch, an output end of the first comparator is connected with the first NOT gate, a control end of the fourth switch is connected with an output end of the first NOT gate, another end of the capacitor is connected with a first end of the fourth switch, and a second end of the fourth switch is grounded.

2. The overvoltage protection circuit of claim 1, wherein, The identification circuit further comprises: A second NOT gate and a third NOT gate, an output end of the second comparator is connected with the second NOT gate and the third NOT gate in sequence, an output of the second NOT gate is connected with a control end of the first switch, and an output of the third NOT gate is connected with a control end of the second switch.

3. The overvoltage protection circuit of claim 2, wherein, The identification circuit further comprises: A fifth switch, the fifth switch is arranged downstream of the attenuation circuit in the second channel, and an output of the third NOT gate is connected with a control end of the fifth switch.

4. The overvoltage protection circuit of claim 1, wherein, The switch is a MOS tube, which is cut off when the input is low and is turned on when the input is high.

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