TW202025588A - Electrostatic discharge protection circuit, sensing device and electronic device including a leakage current elimination unit and an electrostatic discharge removing unit - Google Patents

Abstract

An electrostatic discharge protection circuit includes a leakage current elimination unit and an electrostatic discharge removing unit. The leakage current elimination unit includes a first diode which has an anode coupled to a signal input terminal of a sensing circuit and a cathode coupled to a common mode bias voltage, wherein the common mode bias voltage is an input common mode voltage of the sensing circuit; and a second diode which has a cathode coupled to the signal input terminal and an anode coupled to the common mode bias voltage. The electrostatic discharge removing unit includes a first unidirectional conducting element having an anode coupled to the cathode of the first diode and a cathode coupled to a positive voltage of the system, and a second unidirectional conducting element having an anode coupled to the cathode of the first diode and a cathode coupled to a system ground.

Description

Electrostatic discharge protection circuit, sensing device and electronic device

The present invention relates to an electrostatic discharge (ESD) protection circuit, in particular to an electrostatic discharge protection circuit that can improve the leakage current phenomenon.

With the evolution of semiconductor process technology, the chip area of integrated circuits continues to shrink. However, for integrated circuit chips whose areas continue to shrink, reliability problems also arise, among which electrostatic discharge (ESD) is one of the most important reliability problems. FIG. 1 and FIG. 2 show the structure diagrams of two conventional ESD circuits. As shown in FIG. 1, a group of ESD circuits 1'are electrically connected between an input terminal 3'and an internal circuit 2'of the chip, and it includes two main unidirectional conducting components (hereinafter referred to as "ESD electronic components"). ), a first diode 11' and a second diode 12'. The cathode of the first diode 11' is coupled to the positive working power supply VDD, and the anode is electrically connected to the input terminal 3' And the internal circuit 2'; and the cathode of the second diode 12' is coupled to the negative system power supply VSS (or the system ground GND), and its anode is electrically connected to the input terminal 3'and the internal Between the circuits 2'; wherein, when a positive voltage ESD is generated at the input terminal 3', the ESD energy is transmitted to the system positive working voltage VDD through the first diode 11'; and, when a negative voltage ESD is generated at When the input terminal 3'is input, the ESD energy is transferred to the system ground terminal GND or the system negative working power supply VSS through the second diode 12'.

As shown in FIG. 2, an ESD circuit 4'including a first MOSFET 41' and a second MOSFET 42' is electrically connected to the input terminal 3'and the internal circuit 2'of the chip between. The first MOSFET 41' is a P-type MOSFET, the source of which is coupled to the positive operating power supply VDD of the system, and the drain of which is electrically connected between the input terminal 3'and the internal circuit 2', and Its gate is electrically connected to its source; and the second MOSFET 42' is an N-type MOSFET. Its source is coupled to the negative system power supply VSS (or system ground GND), and its drain Is electrically connected between the input terminal 3'and the internal circuit 2', and its gate is electrically connected to its source; wherein, when a positive voltage ESD is generated at the input terminal 3', the ESD energy passes through the first metal The oxygen half field effect transistor 41' is transmitted to the system positive operating voltage VDD; and, when a negative voltage ESD is generated at the input terminal 3', the ESD energy is transmitted to the system ground through the second metal oxide half field effect transistor 42' Terminal GND or system negative working power VSS.

FIG. 3 shows a structure diagram of a conventional sensing circuit with electrostatic discharge protection capability. It can be seen from FIGS. 1 and 3 that the sensing circuit 5'in FIG. 3 can be regarded as the internal circuit 2'shown in FIG. 1, which includes a switch unit 51' and an analog front-end unit (Analog front-end, AFE). ) 52'; Wherein, the analog front-end unit 52' is, for example, a sample and hold circuit for sampling an analog signal, so that the back-end control and processing unit can further process a plurality of sampling points into digital data . The analog signal conversion is, for example, a charge signal, a current signal, or a voltage signal. Of course, the ESD circuit 4'shown in FIG. 2 can also be applied to the sensing circuit 5'shown in FIG. 3 to provide an electrostatic discharge protection function.

It is worth noting that if an input signal input through the input terminal 3'is a current signal or a charge signal, the leakage current of the aforementioned two ESD circuits will become the noise source of the sensing circuit 5'. For example, as shown in FIG. 3, the reverse saturation current (IS) of the first diode 11' and the second diode 12' made of silicon is usually nA, and IS(T2)= IS(T1)× ; That is to say, as the ambient temperature rises, the reverse saturation current (ie, leakage current) will continue to rise. In view of this, when designing circuit chips, electronic circuit engineers usually reduce the structure size of ESD electronic components to reduce the leakage current of ESD electronic components, so that the circuit chips can fall within the pre-PVT (Process, Voltage, Temperature) error Within range. However, shrinking the structural size of ESD electronic components will reduce the electrostatic discharge protection capabilities of the aforementioned two ESD circuits.

It can be seen from the above description that a novel electrostatic discharge protection circuit is urgently needed in the art.

The main purpose of the present invention is to provide an electrostatic discharge protection circuit, which can add a simple anti-leakage circuit configuration, and when a sensing circuit performs an analog sampling operation, both ends of the anti-leakage circuit configuration See the same voltage, thereby effectively preventing leakage current from interfering with the analog sampling operation. That is to say, when the ESD protection circuit of the present invention is installed in an analog front-end circuit, a clever leakage current prevention mechanism ensures that the analog front-end circuit can complete the alignment under an excellent signal-to-noise ratio. Analog sampling operation of charge signal or current signal.

To achieve the above objective, an electrostatic discharge protection circuit is proposed, which has:

A leakage current elimination unit has: a first diode having an anode coupled to a signal input terminal of a sensing circuit, and a cathode coupled to a common mode bias voltage, wherein the common The mode bias voltage is an input common mode voltage of the sensing circuit; and a second diode having a cathode coupled to the signal input terminal and an anode coupled to the common mode bias voltage; and

An electrostatic discharge discharge unit having: a first unidirectional conduction element, an anode coupled to the cathode of the first diode, and a cathode coupled to a positive system voltage; and a second unit The conducting element has an anode coupled to the cathode of the first diode and a cathode coupled to a system ground.

In a possible embodiment, the sensing circuit is a current sensing circuit or a charge sensing circuit.

In one embodiment, the first unidirectional conducting element and the second unidirectional conducting element are both a diode.

In one embodiment, the first uni-conducting element is a P-type MOSFET, and the second uni-conducting element is an N-type MOSFET.

To achieve the above objective, the present invention further provides an electrostatic discharge protection circuit, which has:

A leakage current elimination unit has: a first diode having an anode coupled to a signal input terminal of a sensing circuit, and a cathode coupled to a common mode bias voltage via a current limiting resistor , Wherein the common-mode bias voltage is an input common-mode voltage of the sensing circuit; and a second diode having a cathode coupled to the signal input terminal, and the first diode The cathode is coupled to an anode; and

An electrostatic discharge discharge unit having: a first unidirectional conduction element, an anode coupled to the cathode of the first diode, and a cathode coupled to a positive system voltage; and a second unit The conducting element has an anode coupled to the cathode of the first diode and a cathode coupled to a system ground.

In one embodiment, the electrostatic discharge protection circuit further includes:

A capacitor, one end of which is coupled to the end of the current limiting resistor and the common mode bias voltage connection, and the other end of the capacitor is coupled to the system ground, so as to form a low-pass filter unit with the current limiting resistor .

To achieve the above objective, the present invention further provides a sensing device, which includes a sensor array and a sensing module, wherein the sensing module is integrated with the aforementioned electrostatic discharge protection circuit, and the sensor array It is a charge sensor array or a current sensor array.

In addition, the present invention also provides an electronic device having the aforementioned sensing device.

In possible embodiments, the electronic device may be a smart phone, a tablet computer, a notebook computer, an all-in-one computer, a smart watch, smart glasses, a digital camera, or an access control device.

In order to enable your reviewer to further understand the structure, features, purpose, and advantages of the present invention, the drawings and detailed descriptions of preferred embodiments are attached as follows.

First embodiment

FIG. 4 shows the structure diagram of the first embodiment of the electrostatic discharge protection circuit of the present invention. The electrostatic discharge protection circuit 1 of the present invention is applied to a sensing circuit 2, especially a sensing circuit used for signal sampling of a charge signal or a current signal. As shown in FIG. 4, the sensing circuit 2 includes a switch unit 21 and an analog front-end (Analog front-end, AFE) unit 22, and the electrostatic discharge protection circuit 1 of the present invention includes: a leakage current elimination unit 11 and a ESD venting unit 12.

The leakage current elimination unit 11 is coupled between a signal input terminal 3 of the sensing circuit 2 and a common mode bias voltage VCOM. It can be inferred that if the sensing circuit 2 is used to sense N sets of analog signals output by a sensor array, the number of signal input terminals 3 and leakage current elimination units 11 will correspondingly increase to N. Moreover, it can be seen from FIG. 4 that the leakage current elimination unit 11 is composed of a first diode 111 and a second diode 112; wherein the first diode 111 is electrically connected to the signal input terminal 3 with its anode. , And the common mode bias voltage VCOM is connected to the cathode of the first diode 111. In addition, the second diode 112 is electrically connected to the signal input terminal 3 and the anode of the first diode 111 with its cathode, and is electrically connected to the cathode of the first diode 111 with its anode. Simply put, the present invention uses two diodes connected back to back to form a so-called leakage current elimination unit 11.

On the other hand, the electrostatic discharge elimination unit 12 is coupled between the leakage current elimination unit 11 and the common mode bias voltage VCOM, and includes a first unidirectional conducting element 121 and a second unidirectional conducting element 122. In this embodiment, the first unidirectional conducting element 121 and the second unidirectional conducting element 122 are both a diode, and the first unidirectional conducting element 121 has a diameter coupled to the cathode of the first diode 111 An anode, and a cathode coupled to a system positive voltage VDD; and the second unidirectional conduction element 122 has an anode coupled to the cathode of the first diode 111 and one of a system ground GND cathode. It should be noted here that the present invention does not limit the diodes as the only implementation aspect of the first unidirectional conducting element 121 and the second unidirectional conducting element 122. In another possible embodiment, the first uni-conducting element 121 is a P-type MOSFET, and the second uni-conducting element 122 is an N-type MOSFET.

In addition, VAin is a signal input to the negative input terminal of the operational amplifier of the analog front-end unit 22, and the common mode bias voltage VCOM is a signal input to the positive input terminal of the operational amplifier of the analog front-end unit 22. It is worth noting that under ideal conditions, the input signal VAin will be equal to the common mode bias voltage VCOM due to the virtual short of the operational amplifier. Therefore, when the switch unit 21 is turned on to perform an analog sampling operation on the charge signal or the current signal, since the voltage at both ends of the leakage current elimination unit 11 is VCOM, the leakage current elimination unit 11 will not generate any leakage current. And interfere with the analog sampling operation. At the same time, even if the first unidirectional conduction element 121 (ie, a diode) and the second unipolar conduction element 122 generate a reverse saturation current (Reverse saturation current, IS), the reverse saturation current will be caused by the leakage current elimination unit 11 It is blocked and cannot flow further into the negative input of the operational amplifier. In other words, the leakage current of the first unidirectional conducting element 121 and the second unidirectional conducting element 122 is absorbed by the common mode bias voltage VCOM, and will not become a noise source of the analog front-end unit 21 of the sensing circuit 2. Therefore, the analog front-end unit 21 can complete the analog sampling operation while maintaining an excellent signal-to-noise ratio regardless of whether the analog front-end unit 21 performs analog sampling operations on charge signals or current signals.

Second embodiment

FIG. 5 shows the structure diagram of the second embodiment of the electrostatic discharge protection circuit of the present invention. Comparing FIGS. 4 and 5, it can be easily found that the second embodiment of the electrostatic discharge protection circuit 1 further includes a current limiting resistor 13, which is coupled between the electrostatic discharge discharge unit 12 and the common mode bias voltage VCOM . Under non-ideal conditions, there may be a voltage difference of several mV between the input signal VAin and the common mode bias voltage VCOM. Therefore, the present invention specifically proposes a second embodiment of the electrostatic discharge protection circuit 1 including the current limiting resistor 13. Wherein, the resistance of the current limiting resistor 13 is a few k ohms to a few M ohms, which can not only play a current limiting function, but also reduce the influence of leakage current caused by the voltage difference between VAin and VCOM. It is worth noting that if the sensing circuit 2 is used to sense N sets of analog signals output by a sensor array, the number of signal input terminals 3 and leakage current elimination units 11 will correspondingly increase to N. At this time, since each signal input terminal 3 must be electrically connected to the common mode bias voltage VCOM, this will result in more and more complicated lines for transmitting the common mode bias voltage VCOM, and consequently generate line noise. At this time, the current-limiting resistor 13 can also isolate the line noise to a certain extent.

The third embodiment

FIG. 6 shows the structure diagram of the third embodiment of the electrostatic discharge protection circuit of the present invention. Comparing FIG. 5 with FIG. 6, it can be easily found that the third embodiment of the electrostatic discharge protection circuit 1 further includes a capacitor 14, one end of which is coupled to the end of the current limiting resistor 13 connected to the common mode bias voltage VCOM. And its other end is coupled to the system ground GND, so as to form a low-pass filter unit with the current limiting resistor 13 to more effectively filter out line noise.

Application examples of the electrostatic discharge protection circuit of the present invention

FIG. 7 is a block diagram of an embodiment of a sensing circuit with the electrostatic discharge protection circuit of the present invention. 6 and 7 at the same time, the sensing circuit 2 includes N switch units 21 and an analog front-end unit 22, wherein each switch unit 21 is electrically connected to a plurality of sensors 41 in a sensor array One sensor, and each sensor 41 includes a photo diode and a source capacitor. It is particularly noted that although the electrostatic discharge protection circuit shown in FIG. 7 is implemented with the architecture shown in FIG. 6, the present invention is not limited to this. On the other hand, the electrostatic discharge protection circuit shown in FIG. 7 includes N leakage current elimination units 11 and one electrostatic discharge elimination unit 12, wherein one end of each leakage current elimination unit 11 is electrically connected to a signal input terminal 3 and One switch unit 21, and the other end is electrically connected to the electrostatic discharge discharge unit 12. The purpose of this design framework is to allow N signal input terminals 3 to share the same ESD discharge unit 12. In this way, for an integrated circuit chip that includes both the sensing circuit and the electrostatic discharge protection circuit of the present invention, not only the ESD capability can be guaranteed, but the area can also be optimized.

In addition, since the existing fingerprint recognition device usually includes a light sensor array and a sensing circuit module (as shown in FIG. 7), and the fingerprint recognition device has also been widely used in various electronic products. The invention further provides an electronic device with the aforementioned sensing circuit, wherein the electronic device can be a smart phone, a tablet computer, a notebook computer, an all-in-one computer, a smart watch, a smart glasses, a digital camera or an access control device .

In this way, the above system has completely and clearly described the electrostatic discharge protection circuit, the sensing device and the electronic device of the present invention; and from the above, it can be seen that the present invention has the following advantages:

1. The electrostatic discharge protection circuit of the present invention can add a simple anti-leakage circuit configuration, and when a sensing circuit performs an analog sampling operation, the two ends of the anti-leakage circuit configuration can see the same voltage , Thereby effectively preventing leakage current from interfering with the analog sampling operation.

2. When the ESD protection circuit of the present invention is installed in an analog front-end circuit, a clever leakage current prevention mechanism ensures that the analog front-end circuit can complete the charge signal under the state of excellent signal-to-noise ratio. Or analog sampling operation of current signal.

It must be emphasized that the foregoing disclosures in this case are preferred embodiments, and any partial changes or modifications that are derived from the technical ideas of this case and are easily inferred by those who are familiar with the art will not deviate from the patent of this case. Right category.

To sum up, regardless of the purpose, means and effects of this case, it is drawn that it is very different from the conventional technology, and its first invention is suitable for practicality, and it does meet the patent requirements of the invention. I implore the examiner to investigate and grant the patent as soon as possible. To benefit society is to pray for the most.

<The present invention> 1: Electrostatic discharge protection circuit 11: Leakage current elimination unit 12: Electrostatic discharge discharge unit 2: Sensing circuit 21: Switch unit 22: Analog front-end unit 3: Signal input terminal 111: first diode 112: second diode 121: The first one-way component 122: The second one-way component 13: current limiting resistor 14: Capacitance 41: Sensor ＜Acquaintances＞ 1’: ESD circuit 2’: Internal circuit 3’: Input 11’: The first diode 12’: The second diode 4’: ESD circuit 41’: The first metal oxide half field effect transistor 42’: The second MOS half-field effect transistor 5’: Sensing circuit 51’: Switch unit 52’: Analog Front End Unit

FIG. 1 shows a structure diagram of a conventional ESD circuit. FIG. 2 shows a structure diagram of another conventional ESD circuit. FIG. 3 shows a structure diagram of a conventional sensing circuit with electrostatic discharge protection capability. FIG. 4 shows the structure diagram of the first embodiment of the electrostatic discharge protection circuit of the present invention. FIG. 5 shows the structure diagram of the second embodiment of the electrostatic discharge protection circuit of the present invention. FIG. 6 shows the structure diagram of the third embodiment of the electrostatic discharge protection circuit of the present invention. Fig. 7 is a block diagram of an embodiment of a sensing circuit with the electrostatic discharge protection circuit of the present invention.

1: Electrostatic discharge protection circuit

11: Leakage current elimination unit

12: Electrostatic discharge discharge unit

2: Sensing circuit

21: Switch unit

22: Analog front-end unit

3: Signal input terminal

111: first diode

112: second diode

121: The first one-way component

122: The second one-way component

Claims (10)

An electrostatic discharge protection circuit, which has: a leakage current elimination unit, has: a first diode, which has an anode coupled to a signal input terminal of a sensing circuit, and a common mode bias voltage coupling Connected to a cathode, where the common mode bias voltage is an input common mode voltage of the sensing circuit; and a second diode having a cathode coupled to the signal input terminal and coupled to the common mode An anode of the bias voltage; and an electrostatic discharge discharge unit having: a first unidirectional conducting element, an anode coupled to the cathode of the first diode, and an anode coupled to a system positive voltage A cathode; and a second unidirectional conduction element having an anode coupled to the cathode of the first diode, and a cathode coupled to a system ground. According to the electrostatic discharge protection circuit described in item 1 of the scope of patent application, the sensing circuit is a charge sensing circuit. According to the electrostatic discharge protection circuit described in item 1 of the patent application, the sensing circuit is a current sensing circuit. In the electrostatic discharge protection circuit described in item 1 of the scope of patent application, the first unidirectional conducting element and the second unidirectional conducting element are both a diode. According to the electrostatic discharge protection circuit described in claim 1 of the patent application, the first unidirectional conducting element is a P-type MOSFET, and the second unidirectional conducting element is an N-type MOSFET. An electrostatic discharge protection circuit, which has: a leakage current elimination unit, has: a first diode, which has an anode coupled to a signal input end of a sensing circuit, and a common The mode bias voltage is coupled to a cathode, wherein the common mode bias voltage is an input common mode voltage of the sensing circuit; and a second diode having a cathode coupled to the signal input terminal, and An anode coupled to the cathode of the first diode; and an electrostatic discharge discharge unit having: a first unidirectional conducting element having one of the cathodes coupled to the first diode An anode, and a cathode coupled to a positive system voltage; and a second unidirectional element having an anode coupled to the cathode of the first diode, and a cathode coupled to a system ground. For example, the electrostatic discharge protection circuit described in item 6 of the scope of the patent application further includes: a capacitor, one end of which is coupled to the end of the current limiting resistor connected to the common mode bias voltage, and the other end is coupled to To the ground of the system, to form a low-pass filter unit with the current limiting resistor. A sensing device includes a sensor array and a sensing module, wherein the sensing module is integrated with an electrostatic discharge protection circuit as described in any one of items 1-7 of the scope of patent application, and the sensor The sensor array is a charge sensor array or a current sensor array. An electronic device having the sensing device described in item 8 of the scope of patent application. For example, the electronic device described in item 9 of the scope of patent application is a group consisting of smart phones, tablets, laptops, all-in-one computers, smart watches, smart glasses, digital cameras, and access control devices. A device of choice.

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