KR20170033999A

KR20170033999A - Fingerprint recognition sensor and system improving sensing offset

Info

Publication number: KR20170033999A
Application number: KR1020150132040A
Authority: KR
Inventors: 전창원
Original assignee: 전창원
Priority date: 2015-09-18
Filing date: 2015-09-18
Publication date: 2017-03-28

Abstract

According to the present invention, disclosed is a fingerprint recognition sensor to improve a sensing offset. The sensor comprises: a fingerprint end capable of being in contact with a finger; a sensing electrode which is connected to a sensing node and serves as one terminal of a sensing capacitor formed by the finger in contact with the fingerprint end; a protection capacitor having one terminal electrically connected to the sensing electrode and the other terminal formed with a protection electrode, wherein the protection electrode receives a protection operation signal; a sensing precharge block to precharge the sensing node with the voltage of a first precharge reference signal in response to a precharge control signal; and a sensing reading block sensing a voltage level of the sensing node to generate sensing data. Moreover, the sensor prevents the sensing electrode from being exposed to the outside and includes a protection electrode to protect the sensing electrode. Therefore, a sensing offset likely to occur during sensing of a fingerprint is largely reduced.

Description

[0001] FINGERPRINT RECOGNITION SENSOR AND SYSTEM IMPROVING SENSING OFFSET [0002]

The present invention relates to a fingerprint recognition sensor, and more particularly, to a fingerprint recognition sensor that improves a sensing offset generated when sensing a fingerprint.

In general, as the information age has come to collect and process desired information, it has become a serious problem that important information of an individual is easily taken or destroyed by others. In addition, the development of electronic commerce and the use of mobile electronic devices have greatly emphasized the need to restrict access to confidentiality and personal data. Accordingly, a fingerprint recognition method for identifying a fingerprint and identifying the fingerprint is widely used as an alternative to a token-based recognition method such as a PIN (Personal Identification Number) or a password input, and a personal identification card and a driver's license.

A fingerprint sensor that realizes a fingerprint recognition method can be classified into an optical type, a capacitive type, a thermal type, a resistive type, and an ultrasonic type according to a fingerprint sensing method have.

U.S. Patent No. 5,940,526 discloses a capacitive fingerprint sensor that recognizes a difference in the amount of charge stored in a sensing capacitor depending on the degree of contact with a finger to recognize the fingerprint.

Since the influence of the parasitic capacitance of each uncharged terminal is insignificant, the above-mentioned patent improves a so-called " sensing offset " in which sensing data is erroneously recognized due to injection and coupling of peripheral electric charges at the time of finger fingerprint sensing It has advantages. However, in the above-mentioned patent, since the input signal is applied to the finger through the external terminal, the sensing electrode contacting the finger must be exposed to the outside.

U.S. Patent 5,940,526

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fingerprint recognition sensor that improves sensing offsets occurring when sensing fingerprints while preventing external exposure of the sensing electrodes.

In order to accomplish the above object, one aspect of the present invention relates to a fingerprint recognition sensor. A fingerprint recognition sensor according to the present invention includes: A sensing electrode connected to the sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger contacting the finger; A protective capacitor electrically connected to the sensing electrode, and a protective electrode connected to the other terminal, the protective electrode receiving the protective driving signal; A sensing precharged block which is driven to precharge the sensing node to a voltage of a first precharge reference signal in response to a precharge control signal; And a sensing read block for sensing the voltage level of the sensing node to generate sensing data.

According to an aspect of the present invention, there is provided a fingerprint recognition system including a plurality of pixels and a sensing read block. Wherein each of the plurality of pixels comprises: A sensing electrode connected to the sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger contacting the finger; A protective capacitor electrically connected to the sensing electrode, and a protective electrode connected to the other terminal, the protective electrode receiving the protective driving signal; And a sensing free-charge block driven to precharge the sensing node to a voltage of the first pre-charge reference signal in response to the free-charge control signal. The sensing read block includes a sensing read block for sensing the voltage level of the sensing node of the selected pixel to generate sensing data at the sensing sensing time. The sensing electrode and the protective electrode of at least some of the pixels adjacent to the selected pixel at the sensing operation are controlled to the same voltage as the sensing electrode and the protective electrode of the selected pixel.

In the fingerprint recognition sensor of the present invention, a protective electrode for shielding external sensing of the sensing electrode and for protecting the sensing electrode is disposed. Therefore, according to the fingerprint recognition sensor of the present invention, the sensing offset that can be generated at the time of sensing the fingerprint is greatly improved.

A brief description of each drawing used in the present invention is provided.
1 is a view conceptually showing a fingerprint recognition sensor according to an embodiment of the present invention.
FIGS. 2 and 3 are timing charts for explaining the operation of the fingerprint recognition sensor of FIG. 1. FIG.
Fig. 4 is a diagram showing an example of the feedback capacitor means of Fig. 1;
FIG. 5 is a cross-sectional view showing the formation of the sensing electrode and the protective electrode in FIG. 1, and FIG. 6 is a layout view of the sensing electrode and the protective electrode in FIG.
FIG. 7 is a diagram for explaining that factors that cause a 'sensing offset' from neighboring pixels can be injected during sensing of a selected pixel.
8 is a diagram showing an example in which a modified feedback capacitor means is applied in the fingerprint recognition sensor of FIG.
FIG. 9 is a detail view of the feedback capacitor means of FIG. 8 together with associated components. FIG.

For a better understanding of the present invention and its operational advantages, and the objects attained by the practice of the present invention, reference should be made to the accompanying drawings, which illustrate preferred embodiments of the invention, and the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are being provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

It should be noted that, in understanding each of the drawings, the same members are denoted by the same reference numerals whenever possible. Further, detailed descriptions of known functions and configurations that may be unnecessarily obscured by the gist of the present invention are omitted.

In the drawings, the thickness is enlarged in order to clearly illustrate the various layers. It is to be understood that, in the drawings, the description is made in the context of an observer and, when a layer or the like is referred to as being "on" another portion, it includes not only the portion directly above but also another portion in between. Conversely, when a part is referred to as being "directly on" another part, it means that there is no other part in the middle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view conceptually showing a fingerprint recognition sensor according to an embodiment of the present invention. 2 and 3 are timing charts for explaining the operation of the fingerprint recognition sensor of FIG.

The sensing operation of the fingerprint recognition sensor of the present invention is performed through a signal sensing operation P1 (see FIG. 2) and a reference sensing operation P2 (see FIG. 3), which are distinguished from each other. The signal sensing operation P1 may be classified into a signal free chasing process (P11 in FIG. 2) and a signal sensing process (P12 in FIG. 2) (P21 in FIG. 3) and a reference sensing process (P22 in FIG. 3).

In this specification, the signal free charge process (P11 in FIG. 2) and the reference free charge process (P21 in FIG. 3) may be referred to as a 'free charge process' P12) and the reference sensing process (P22 in FIG. 3) may be collectively referred to as a 'sensing process'.

1 and 2, the fingerprint sensor of the present invention includes a fingerprint sensor STF, a sensing electrode ELDT, a protective capacitor CPDR, a sensing free-charge block BKSNPR, (BKSNDR).

The finger STF is capable of contacting the finger FNG. The sensing electrode ELDT is electrically connected to the sensing node NSEN.

When the finger FNG is brought into contact with the ground finger STF, the sensing electrode ELDT and the finger FNG serve as one terminal and the other terminal of the virtual sensing capacitor CPDT, respectively. Further, the finger FNG is grounded through the user's body.

At this time, the amount of charge stored in the sense capacitor CPDT depends on the degree of contact of the finger FNG. That is, the greater the degree of contact of the finger FNG, the greater the amount of charge stored in the sense capacitor CPDT. In the fingerprint recognition sensor of the present invention, the ridge of the finger, that is, the fingerprint is recognized by checking the amount of charge stored in the sense capacitor CPDT.

One terminal of the protection capacitor CPDR is electrically connected to the sensing electrode ELDT and the other terminal is a protection electrode ELIN. The protective electrode ELIN applies a protective driving signal XDRDT.

In the fingerprint sensor of the present invention, the protective electrode ELIN, which is another terminal of the protection capacitor CPDR, blocks the unintentional charge injected into the sensing electrode ELDT.

The formation of the sensing electrode ELDT and the protective electrode ELIN will be described later in detail.

In the sensing operation of the fingerprint sensor of the present invention, the voltage level of the protection driving signal XDRDT applied to the protective electrode ELIN is controlled to the same level as the sensing electrode ELDT. Therefore, the amount of charge stored in the protection capacitor CPDR is '0'.

The sensing free charge block BKSNPR is driven so as to precharge the sensing node NSEN to the voltage of the first free potential reference signal XPRE1 in the free charge process P11 and P21.

In the present embodiment, the first precharge reference signal XPRE1 has an upper driving voltage VHG in the signal sensing operation P1 and a lower driving voltage VLW in the reference sensing operation P2. At this time, the upper driving voltage VHG is higher than the lower driving voltage VLW.

Preferably, the sensing precharged block (BKSNPR) comprises a free-charge switch (SWPR) controlled by a precharge control signal (XPCON).

At this time, the free-charge switch SWPR is turned on in the free charge process P11 or P21 and turned off in the sensing process P12 or P22.

The sensing read block BKSNDR senses the voltage level of the sensing node NSEN to generate sensing data DSEN to confirm the degree of contact of the finger FNG with respect to the ground fault STF.

At this time, the sensing data DSEN indicates the difference between the voltage levels of the signal data SDA and the reference data RDA. Here, the signal data SDA is generated in the signal sensing operation P1 and the reference data RDA is generated in the reference sensing operation P2.

The sensing read block (BKSNDR) specifically includes a sensing selection switch (SWST), a sensing driver (100), and a compensator (200).

The sensing selection switch SWST is turned on in response to the sensing control signal XSCON in sensing steps P12 and P22 and is driven to connect the sensing node NSEN to the driving node NDRV. The sensing selection switch SWST is turned off in the precharging process (P11, P21).

The sensing driver 100 senses a voltage level of the driving node NDRV to generate sensing data DSEN. That is, the sensing driver 100 generates the signal data SDA by sensing the voltage level of the driving node NDRV in the signal sensing process P12, and in the sensing sensing process P22, the driving node NDRV ) To generate reference data RDA.

More specifically, the sensing driving unit 100 includes a driving amplifier 110, a reset switch 120, a feedback capacitor unit (MSCP), and a sampling and holding unit 140.

The driving amplifier 110 inverts and amplifies the voltage of the driving node NDRV by comparing the voltage of the driving node NDRV with the amplification reference voltage VRF. Here, it is preferable that the amplification reference voltage VRF has a level lower than the lower driving voltage VLW.

At this time, the driving amplifier 110 generates the signal data SDA in the signal sensing process P12, and is held by the sampling and holding means 140. FIG. The driving amplifier 110 generates the reference data RDA in the reference sensing process P22 and is held by the sampling and holding means 140. [

The reset switch 120 electrically connects the output node N111 of the driving amplifier 110 to the driving node NDRV in response to a reset signal RST. Here, the reset switch 120 is turned on in the free charge process (P11, P21) and turned off before the sensing process (P12, P22) is started.

Accordingly, the output node N111 and the driving node NDRV of the driving amplifier 110 are both controlled at the same level of the amplification reference voltage VRF in the precharge process P11 and P21.

The feedback capacitor means (MSCP) couples the driving node (NDRV) to the output node (N111) of the driving amplifier. Accordingly, the driving node NDRV is restored to the amplified reference voltage VRF even after sensing in the sensing process P12 and P22.

Meanwhile, in the present embodiment, the gain factor Ga of the driving amplifier 110 is expressed by Equation (1).

(1)

Ga = - (Ca / Cg)

Here, Ca is the capacitance of the sense capacitor CPDT and Cg is the capacitance of the capacitor formed between the drive node NDRV and the output node which is the input node of the drive amplifier 110 during sensing Quot; capacitance ").

Advantageously, said feedback capacitor means (MSCP) has a capacitance which is varied by a capacitance control signal (XCAP). In this case, the gain of the driving amplifier 110 can be appropriately controlled. For reference, in this embodiment, adjustment of the capacitance Ca of the sense capacitor CPDT is difficult.

4 is a diagram showing an example of the feedback capacitor means (MSCP) of FIG.

Referring to FIG. 4, the feedback capacitor means MSCP includes a first drive feedback capacitor 131, a second drive feedback capacitor 133, and a drive feedback switch 135.

One end of the first drive feedback capacitor 131 is connected to the drive node NDRV and the other end of the first drive feedback capacitor 131 is connected to the output node N111 of the drive amplifier 110. [ One end of the second driving feedback capacitor 133 is connected to the driving node NDRV.

The drive feedback switch 135 is driven to connect the other end of the second drive feedback capacitor 133 to the output node N111 of the drive amplifier in response to activation of the capacitance control signal XCAP.

According to the feedback capacitor means MSCP having the configuration of FIG. 4, the driving capacitance Cg is varied depending on whether the capacitance control signal XCAP is activated or not, and ultimately, the gain factor of the driving amplifier 110 Ga are controlled.

Referring again to FIG. 1, the sampling and holding means 140 samples and holds the voltage of the output node N111 of the driving amplifier 110 to generate the sensing data DSEN. That is, in the signal sensing step P12, the sampling and holding means 140 samples and holds the signal data SDA provided through the output node N111 of the driving amplifier 110. [ The sampling and holding means 140 samples and holds the reference data RDA provided through the output node N111 of the driving amplifier 110 in the reference sensing process P22.

At this time, the sensing data DSEN is a voltage difference value between the signal data SDA and the reference data RDA.

In the fingerprint recognition sensor of FIG. 1, it is ideal that the gain factor of the driving amplifier 110 is determined by a ratio of a capacitance value of the sense capacitor CPDT to a capacitance value of the feedback capacitive means MSCP.

However, an unintentional parasitic capacitor (CPPD) may be generated in the sensing node NSEN. The parasitic capacitor CPPD may cause a 'sensing offset' during sensing of the fingerprint sensor.

In order to exclude the influence of the parasitic capacitor CPPD, the sensing read block BKSNDR in the fingerprint recognition sensor of the present invention includes the compensation unit 200.

The compensation unit 200 is connected to the driving node NDRV and is driven to compensate for the influence of a parasitic capacitor CPPD generated in the sensing node NSEN.

Specifically, the compensation unit 200 includes a compensation capacitor CPSA, a first compensation switch 230, and a second compensation switch 250.

The compensation capacitor CPSA has a capacitance value corresponding to a capacitance value of the parasitic capacitor CPPD. Preferably, the capacitance value of the compensation capacitor CPSA is equal to the capacitance value of the parasitic capacitor CPPD.

The first compensation switch 230 is driven to electrically connect one terminal of the compensation capacitor CPSA to the second precharge reference signal XPRE2 in response to the precharge control signal XPCON.

In the present embodiment, the second precharge reference signal XPRE2 has a lower driving voltage VLW in the signal sensing operation P1 and an upper driving voltage VHG in the reference sensing operation P2.

The second compensation switch 250 is driven to electrically connect one terminal of the compensation capacitor CPSA to the driving node NDRV in response to the sensing control signal XSCON.

Next, the amount of charge that affects the sensing data (DSEN) at the time of sensing the fingerprint sensor of the present invention will be examined.

As described above, the sensing of the fingerprint recognition sensor of the present invention is performed through a signal sensing operation P1 (see FIG. 2) and a reference sensing operation P2 (see FIG. 3), which are distinguished from each other. The signal sensing operation P1 may be divided into a signal pre-charge process P11 and a signal sensing process P12. The reference sensing operation P2 includes a reference precharge process P21, And a process (P22).

First, a net charge quantity Qsig that affects the value of the signal data SDA provided to the drive amplifier 110 in the signal sensing operation P1 will be described.

First, the charge amount of each capacitor in the signal free charge process (P11) is as shown in Table 1.

Capacitor (Capacitance) Charge amount CPDT (Ca) VHG * Ca CPPD (Cb) VHG * Cb CPDR (Cc) 0 * Cc CPSA (Cd) VLW * Cd

That is, in the signal free charge process P11, the total charge amount Qsp is equal to (Equation 2).

(2)

Qsp = VHG * Ca + VHG * Cb + VLW * Cd

The charge amount of each capacitor in the signal sensing process (P12) is shown in Table 2.

Capacitor (Capacitance) Charge amount CPDT (Ca) VRF * Ca CPPD (Cb) VRF * Cb CPDR (Cc) 0 * Cc CPSA (Cd) VRF * Cd

That is, in the signal sensing process P12, the total charge amount Qss is equal to (Equation 3).

(3)

Qss = VRF * Ca + VRF * Cb + VRF * Cd

Therefore, the net charge amount Qsig that affects the value of the signal data SDA provided to the drive amplifier 110 in the signal sensing operation P1 is expressed by Equation (4).

(4)

Qsig = Qsp-Qss

= (VHG-VRF) * Ca + (VHG-VRF) * Cb + (VLW-VRF) * Cd

Next, the net charge amount Qref affecting the value of the reference data RDA provided to the drive amplifier 110 in the reference sensing operation P2 will be examined.

First, the charge amount of each capacitor in the reference free charge process (P21) is as shown in Table 3.

Capacitor (Capacitance) Charge amount CPDT (Ca) VLW * Ca CPPD (Cb) VLW * Cb CPDR (Cc) 0 * Cc CPSA (Cd) VHG * Cd

That is, the total charge amount Qrp in the reference free charge process P21 is equal to (Equation 5).

(5)

Qrp = VLW * Ca + VLW * Cb + VHG * Cd

The charge amount of each capacitor in the reference sensing process (P22) is as shown in Table 4.

That is, in the reference sensing process P12, the total charged amount Qrs is equal to (Equation 6).

(6)

Qrs = VRF * Ca + VRF * Cb + VRF * Cd

Therefore, the net charge amount Qref that affects the value of the reference data RDA provided to the drive amplifier 110 in the reference sensing operation P2 is expressed by Equation (7).

(7)

Qref = Qrp-Qrs

= (VLW-VRF) * Ca + (VLW-VRF) * Cb + (VHG-VRF) * Cd

The amount of charge that affects the sensing data DSEN during operation of the fingerprint recognition sensor of the present invention affects the value of the signal data SDA provided to the driving amplifier 110 in the signal sensing operation P1 Is the difference between the net charge Qsig and the net charge Qref which affects the value of the reference data RDA provided to the drive amplifier 110 in the reference sensing operation P2.

Therefore, the amount of charge Qsen affecting the sensing data DSEN during operation of the fingerprint sensor of the present invention is expressed by Equation (8).

(8)

Qsen = Qsig-Qref

= (VHG-VLW) * Ca + (VHG-VLW) * Cb + (VLW-VHG) * Cd

When the capacitance value Cd of the compensation capacitor CPSA is equal to the capacitance value Cb of the parasitic capacitor CPPD, the amount Qsen of the charge affecting the sensing data DSEN is Equation (9) is the same.

(9)

Qsen = (VHG-VLW) * Ca

That is, in the fingerprint sensor of the present invention, the sensing data DSEN is determined by the capacitance value Ca of the sensing capacitor CPDT, and the influence of the capacitance value Cb of the parasitic capacitor CPPD is excluded .

Therefore, according to the fingerprint recognition sensor of the present invention, accurate fingerprint recognition is possible.

Meanwhile, the compensation capacitor CPSA preferably has an externally adjustable capacitance. In this case, the compensation capacitor CPSA can easily have a capacitance value (for example, the same) corresponding to the capacitance value of the parasitic capacitor CPPD.

In this embodiment, the data value of the sensing data DSEN depends on the output difference Vdiff of the driving amplifier 110 in the signal sensing operation P1 and the reference sensing operation P2.

At this time, the output difference (Vdiff) of the drive amplifier 110 is expressed by Equation (10).

(10)

Vdiff = Ga * (VHG-VLW)

= - (Ca / Cg) * (VHG-VLW)

That is, in the fingerprint recognition sensor of the present invention, by controlling the difference between the upper driving voltage VHG and the lower driving voltage VLW and the driving capacitance Cg, the sensing data DSEN can have an appropriate data value .

Next, the formation of the sensing electrode ELDT and the protective electrode ELIN in the fingerprint sensor of Fig. 1 will be described in detail.

FIG. 5 is a cross-sectional view showing the formation of the sensing electrode ELDT and the protective electrode ELIN of FIG. 1, and FIG. 6 is a layout view of the sensing electrode ELDT and the protective electrode ELIN of FIG. 5 and 6, components directly relating to the present invention are shown centrally, and the remaining components are omitted or schematically shown.

As shown in FIGS. 5 and 6, the protective electrode ELIN is formed of a first metal layer MET1 formed on the substrate SUB. At this time, the protective driving signal XDRDT is applied to the protective electrode ELIN formed of the first metal layer MET1 as described above.

In FIG. 5, 'LMUS' conceptually represents various kinds of materials including an insulating layer that can be formed between the first metal layer MET1 and the substrate SUB.

The sensing electrode ELDT is formed of a second metal layer MET2 stacked on the first metal layer MET1 forming the protective electrode ELIN.

At this time, the protective driving signal XDRDT is applied to the protective electrode ELIN formed of the first metal layer MET1 as described above. In this case, the sensing electrode ELDT formed by the second metal layer MET2 is electrically connected to the sensing electrode EL1 through sensing electrodes, such as a sensing offset Can be protected from factors that can generate '

A protective dielectric layer LPRF of a dielectric material is formed between the second metal layer MET2 forming the sensing electrode ELDT and the first metal layer MET1 forming the protective electrode ELIN.

Accordingly, a protection capacitor CPDR having the sensing electrode ELDT as one terminal and the protective electrode ELIN as the other terminal is formed.

The ground electrode STF is formed of a surface dielectric layer LSUR of a dielectric material stacked on the second metal layer MET2 forming the sensing electrode ELDT.

At this time, when the finger FNG is brought into contact with the ground finger STF, the sensing electrode ELDT and the finger FNG act as one terminal and the other terminal of the virtual sensing capacitor CPDT, Same as.

Since the sensing electrode ELDT formed as described above is covered with the surface dielectric layer LSUR, the sensing electrode ELDT is not exposed to the outside.

Preferably, the surface dielectric layer LSUR comprises a first surface dielectric layer LSUR1 and a second surface dielectric layer LSUR2. The first surface dielectric layer LSUR1 is formed on the second metal layer MET2 forming the sensing electrode ELDT.

As shown in FIGS. 5 and 6, the first metal layer MET1 is formed on the first surface dielectric layer LSUR1 and penetrates the first surface dielectric layer LSUR1 and the protective dielectric layer LPRF, The third metal layer MET3 that is in contact contact also acts as the protective electrode ELIN.

The second surface dielectric layer LSUR2 is formed on the first surface dielectric layer LSUR1 on which the third metal layer MET3 is formed.

In this case, the sensing electrode ELDT formed of the second metal layer MET2 can be formed not only from the bottom but also from off-set generation factors such as peripheral charge and coupling effect that can be injected from the side Can be protected.

On the other hand, the fingerprint recognition system generally includes a plurality of fingerprint recognition pixels. The fingerprint recognition pixels may include the sensing electrode ELDT and the protective electrode ELIN of the fingerprint recognition sensor of the present invention.

At this time, as shown in FIG. 7, factors which cause a 'sensing offset' may be injected from surrounding pixels BPIX at the time of sensing the selected pixel SPIX.

In this case, at least a part of the sensing electrodes ELDT and the protective electrodes ELIN disposed in the periphery of the selected pixel SPIX, that is, at least a part of the adjacent pixels BPIX, The sensing electrode ELDT of the selected pixel SPIX can be more effectively protected from off-set generating factors by controlling the same voltage as the ELDT and the protecting electrode ELIN.

Meanwhile, in the fingerprint sensor of FIG. 1, the feedback capacitor means MSCP can be modified into various forms.

8 is a diagram showing an example in which a modified feedback capacitor means is applied in the fingerprint recognition sensor of FIG.

In the fingerprint sensor of Fig. 8, a modified feedback capacitor means MSCP 'is formed between the output node N111 of the drive amplifier 110 and the sensing node NSEN.

FIG. 9 is a view showing in detail the feedback capacitor means MSCP 'of FIG. 8 together with the relevant components.

9, the feedback capacitor means MSCP includes a first sensing feedback capacitor 171 and a second sensing feedback capacitor 172, a first sensing feedback switch 173, a second sensing feedback switch 174, A third sensing feedback switch 175 and a fourth sensing feedback switch 176.

One side of the first sensing feedback capacitor 171 and the second sensing feedback capacitor 172 are connected to the sensing node NSEN.

The first sensing feedback switch 173 electrically connects the other side of the first sensing feedback capacitor 171 to the output node N111 of the driving amplifier 110 in response to the sensing control signal XSCON. .

The second sensing feedback switch 174 electrically connects the other side of the first sensing feedback capacitor 171 and the other side of the second sensing feedback capacitor 172 in response to the activation of the capacitance control signal XCAP .

The third sensing feedback switch 175 electrically connects the other side of the first sensing feedback capacitor 171 to the first precharge reference signal XPRE1 in response to the precharge control signal XPCON. .

The fourth sensing feedback switch 176 electrically connects the other side of the second sensing feedback capacitor 172 to the protection driving signal XDRDT in response to deactivation of the capacitance control signal XCAP .

9, when the capacitance control signal XCAP is activated, the sensing control signal XSCON is activated and the first sensing feedback capacitor 171 is turned on, And the second sensing feedback capacitor 172 are formed in parallel with the output node N111 of the driving amplifier 110 and the driving node NDRV.

That is, when the capacitance control signal XCAP is activated, the driving capacitance Cg becomes large.

When the capacitance control signal XCAP is inactivated, the second sensing feedback capacitor 172 and the protection capacitor CPDR are formed in parallel between the sensing node NSEN and the protection driving signal XDRT.

That is, when the capacitance control signal XCAP is inactivated, the driving capacitance Cg is reduced and the second sensing feedback capacitor 172 enhances the action of the protection capacitor CPDR.

According to the fingerprint recognition sensor of the present invention, the external exposure of the sensing electrode is blocked, and the fingerprint can be recognized with high accuracy.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

For example, it is apparent to those skilled in the art that various switches in the present specification can be implemented in various forms such as a PMOS transistor, an NMOS transistor, a transmission gate, and the like.

Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims

In the fingerprint recognition sensor,
A paragraph of whether a finger is touchable;
A sensing electrode connected to the sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger contacting the finger;
A protective capacitor electrically connected to the sensing electrode, and a protective electrode connected to the other terminal, the protective electrode receiving the protective driving signal;
A sensing precharged block which is driven to precharge the sensing node to a voltage of a first precharge reference signal in response to a precharge control signal; And
And a sensing reading block for sensing the voltage level of the sensing node to generate sensing data.

The method of claim 1, wherein the sensing read block
A sensing selection switch responsive to the sensing control signal for connecting the sensing node to the driving node;
A sensing driver for sensing the voltage level of the driving node to generate sensing data; And
And a compensator coupled to the drive node and driven to compensate for an influence of parasitic capacitance generated in the sensing node during a sensing operation of the sensing driver.

3. The apparatus of claim 2, wherein the sensing driver
A driving amplifier for inverting and amplifying a voltage of the driving node with an amplification reference voltage;
A reset switch responsive to a reset signal, the reset switch being driven to electrically connect an output node of the drive amplifier to the drive node;
Feedback capacitor means coupling the drive node to an output node of the drive amplifier; And
And sampling and holding means for sampling and holding the voltage of the output node of the driving amplifier to generate the sensing data.

4. The apparatus of claim 3, wherein the feedback capacitor means
And has a variable capacitance in response to a capacitance control signal.

5. The apparatus of claim 4, wherein the feedback capacitor means
A first driving feedback capacitor having one side connected to the driving node and the other side connected to an output node of the driving amplifier;
A second driving feedback capacitor having one side connected to the driving node; And
And a drive feedback switch which is driven to connect the other end of the second drive feedback capacitor to the output node of the drive amplifier in response to the activation of the capacitance control signal.

5. The apparatus of claim 4, wherein the feedback capacitor means
A first sensing feedback capacitor and a second sensing feedback capacitor, one side of which is connected to the sensing node;
A first sensing feedback switch responsive to the sensing control signal for electrically connecting the other side of the first sensing feedback capacitor to an output node of the driving amplifier;
A second sensing feedback switch electrically connecting the other side of the first sensing feedback capacitor and the other side of the second sensing feedback capacitor in response to activation of the capacitance control signal;
A third sensing feedback switch responsive to the free charge control signal, the third sensing feedback switch being driven to electrically connect the other side of the first sensing feedback capacitor to the first free potential reference signal;
And a fourth sensing feedback switch which is driven to electrically connect the other side of the second sensing feedback capacitor to the protection driving signal in response to deactivation of the capacitance control signal.

3. The apparatus of claim 2, wherein the compensation unit
A compensation capacitor having a capacitance value corresponding to the parasitic capacitor;
A first compensation switch driven in response to the free charge control signal to electrically connect one terminal of the compensation capacitor to a second free charge reference signal;
And a second compensation switch which is driven to electrically connect one terminal of the compensation capacitor to the drive node in response to the sensing control signal.

The method according to claim 1,
The protective electrode
A first metal layer stacked on the substrate,
The sensing electrode
And a second metal layer laminated on the first metal layer forming the protective electrode,
The above paragraph
And a surface dielectric layer laminated on the second metal layer forming the sensing electrode.

9. The method of claim 8, wherein the surface dielectric layer
A first surface dielectric layer laminated on the second metal layer forming the sensing electrode; And
And a second surface dielectric layer overlying the first surface dielectric layer,
The protective electrode
A third metal layer formed on the first surface dielectric layer and in contact contact with the first metal layer through the first surface dielectric layer and the protective dielectric layer, the protective dielectric layer being formed between the first metal layer and the second metal layer And the third metal layer.

A fingerprint recognition system comprising a plurality of pixels and a sensing read block,
Each of the plurality of pixels
A paragraph of whether a finger is touchable;
A sensing electrode connected to the sensing node, the sensing electrode being one terminal of a sensing capacitor formed by the finger contacting the finger;
A protective capacitor electrically connected to the sensing electrode, and a protective electrode connected to the other terminal, the protective electrode receiving the protective driving signal; And
And a sensing free chopper block responsive to the free chopper control signal and driven to precharge the sensing node to a voltage of a first precharge reference signal,
The sensing read block
And a sensing read block which senses a voltage level of the sensing node of the selected pixel at the sensing operation to generate sensing data,
Wherein the sensing electrode and the protective electrode of at least some of the pixels adjacent to the selected pixel at the sensing < RTI ID = 0.0 >
Wherein the voltage is controlled to the same voltage as the sensing electrode and the protective electrode of the selected pixel.