CN102315633A

CN102315633A - Electrostatic protection circuit

Info

Publication number: CN102315633A
Application number: CN2010102262922A
Authority: CN
Inventors: 吴健铭; 曹太和
Original assignee: Realtek Semiconductor Corp
Current assignee: Realtek Semiconductor Corp
Priority date: 2010-07-06
Filing date: 2010-07-06
Publication date: 2012-01-11
Anticipated expiration: 2030-07-06
Also published as: CN102315633B

Abstract

The invention discloses an electrostatic protection circuit. The electrostatic protection circuit comprises a sub-voltage generating circuit, a judgment circuit and a switch circuit, wherein the sub-voltage generating circuit outputs a first voltage and a second voltage; the judgment circuit is coupled with the sub-voltage generating circuit and is used for receiving the first voltage and the second voltage and determining the voltage level of an output voltage according to the first voltage and the second voltage; the switch circuit is coupled with the judgment circuit and is used for judging whether the switch circuit is switched on or not according to the output voltage; and the transient voltage of the first voltage is different from the transient voltage of the second voltage.

Description

Electrostatic discharge protection circuit

Technical field

The present invention relates to a kind of electronic circuit, refer to a kind of electrostatic discharge protection circuit especially.

Background technology

(Electrostatic Discharge is to cause most of electronic components to receive the excessively electrically principal element of stress rupture ESD) to static discharge, and this destruction can cause electronic component to form a kind of nonvolatil breaking-up, thereby influences the normal operation of electronic component.Generally speaking, can utilize an electrostatic discharge protection circuit to avoid the destruction of static discharge.

Whether traditional electrostatic discharge protection circuit is that the speed of utilizing voltage to rise differentiates is static discharge; If yet it is too fast that starting up speed takes place; It is too rapid to cause voltage to rise; It is normal boot-strap that traditional electrostatic discharge protection circuit can't be told, and causes electrostatic discharge protection circuit by error starting, makes a unexpected electric current pass through electrostatic discharge protection circuit.

Summary of the invention

One of the object of the invention is to provide a kind of electrostatic discharge protection circuit, and it can avoid unexpected misoperation to take place.

One of the object of the invention is to provide a kind of electrostatic discharge protection circuit, its can avoid because of the start behavior by error starting.

Of the present inventionly one of solid be to provide a kind of electrostatic discharge protection circuit, it can avoid rising by error starting at a high speed because of the power source charges transient voltage.

One of the object of the invention provides a kind of electrostatic discharge protection circuit, can avoid because of the voltage excessive velocities by error starting.

One embodiment of the invention provide a kind of electrostatic discharge protection circuit, have a first node, and in order to receive an input voltage, electrostatic discharge protection circuit comprises a dividing potential drop and produces circuit, a decision circuitry and a switching circuit.Dividing potential drop produces circuit and exports one first voltage, one second voltage, and wherein, first voltage, second voltage is in order to the variation situation of the voltage that reflects input voltage, and wherein, the voltage of the voltage of first voltage and second voltage is inequality.Decision circuitry couples dividing potential drop and produces circuit, receives first voltage, second voltage, and determines the voltage quasi position of an output voltage according to first voltage, second voltage.Switching circuit couples decision circuitry, and according to the accurate position determine switch circuit turn-on state of output voltage.

Electrostatic discharge protection circuit of the present invention can be told static discharge or normal working voltage under the quick situation of voltage, thereby avoids the electrostatic discharge protection circuit misoperation.

Description of drawings

Fig. 1 is the embodiment sketch map that electrostatic discharge protection circuit of the present invention is shown.

Fig. 2 A be one embodiment of the invention is shown electrostatic discharge protection circuit when circuit just starts, the voltage voltage analogous diagram under the rapid situation that rises

Fig. 2 B is the current simulations figure that illustrates corresponding to Fig. 2 A.

Fig. 3 A illustrates the electrostatic discharge protection circuit of one embodiment of the invention at electrostatic potential V _ESDVoltage analogous diagram under the situation about taking place.

Fig. 3 B is the current simulations figure that illustrates corresponding to Fig. 3 A.

Fig. 4 is the embodiment sketch map that electrostatic discharge protection circuit of the present invention is shown.

Fig. 5 is the embodiment sketch map that electrostatic discharge protection circuit of the present invention is shown.

Fig. 6 is the embodiment sketch map that electrostatic discharge protection circuit of the present invention is shown.

Fig. 7 A be one embodiment of the invention is shown electrostatic discharge protection circuit when circuit just starts, the voltage voltage analogous diagram under the rapid situation that rises

Fig. 7 B is the current simulations figure that illustrates corresponding to Fig. 7 A.

Fig. 8 A is the electrostatic discharge protection circuit that one embodiment of the invention is shown, at electrostatic potential V _ESDVoltage analogous diagram under the situation about taking place.

Fig. 8 B is the current simulations figure that illustrates corresponding to Fig. 8 A.

[main element symbol description]

100,200,300,400,500,600 electrostatic discharge protection circuits

101,401 dividing potential drops produce circuit

101a, 101b, 201a, 201b, 301a, 301b, 401a, 401b, 401c resistance

101c, 401d electric capacity

102,402 decision circuitry

102a, 102b, 402a, 402b switch

103,403 switching circuits

N1, N2, N3, Nj node

Embodiment

Fig. 1 is the embodiment sketch map that electrostatic discharge protection circuit of the present invention is shown.As shown in Figure 1, electrostatic discharge protection circuit 100 comprises a dividing potential drop and produces circuit 101, a decision circuitry 102 and a switching circuit 103.Electrostatic discharge protection circuit 100 has a node N1, is to be used for receiving an input voltage vin, and is in the rate of climb during the transient state according to the voltage swing of input voltage vin and input voltage vin, whether determines conducting (On) switching circuit 103.When switching circuit 103 was switched on, then electric current was released into earth potential G through switching circuit 103.

In one embodiment, as shown in Figure 1, dividing potential drop produces circuit 101 can comprise

resistance

101a, 101b and electric capacity 101c.The end of resistance 101a couples node N1, other end series resistance 101b.Decision circuitry 102 is coupled to the node N2 between

resistance

101a and 101b, and electric capacity 101c couples resistance 101b, and decision circuitry 102 is coupled to the node N3 between resistance 101b and electric capacity 101c, and node N2 and N3 difference output voltage V p and Vn.

Note that among the embodiment, if

resistance

101a and 101b are for connect, then the voltage swing of its voltage Vp and Vn be according to

resistance

101a, 101b, reach electric capacity 101c resistance value big or small and determine.Another embodiment, the number of resistance and electric capacity and coupling mode (for example series-parallel system) all can be determined by the designer, are not restricted to this; In addition, resistance and/or electric capacity also can be implemented by the present existing or future various semiconductor elements that develop, for example transistor ... etc.

One embodiment, as shown in Figure 1, decision circuitry 102 can comprise switch 102a and 102b.Node N2, the other end that the end of switch 102a couples dividing potential drop generation circuit 101 couple input voltage vin, and the other end couples switch 102b and forms a node Nj; The end of switch 102b couples that node N3, the other end that dividing potential drop produces circuit 101 couple node Nj and the other end couples an earth potential G.

Switch 102a and 102b receive voltage Vp and Vn respectively, determine an output voltage V 3 according to voltage Vp and Vn, so decision circuitry 102 can change because of the voltage swing of voltage Vp and Vn, the voltage quasi position of output voltage V 3 are also changed.

Among one embodiment, switch 102a can be a P-type mos field-effect transistor and realizes, switch 102b is that a N type metal oxide semiconductor field-effect transistor is realized.Certainly, among another embodiment,

switch

102a, 102b are not limited to this, and it can be implemented by other present existing or future semiconductor element that develops.

Like the example of Fig. 1, the source electrode of switch 102a couples node N1 and receives input voltage vin, and the grid of switch 102a flows through the size of switch 102a according to size decision conducting state, nonconducting state or the electric current of voltage Vp.In addition, conducting voltage V1 is the voltage difference (being V1=Vin-Vp) of input voltage vin and voltage Vp, and conducting voltage V2 is the voltage difference (being V2=Vn-0) of voltage Vn and earth potential G.Accordingly, the drain electrode of switch 102b couples the drain electrode of switch 102a, and the source electrode of switch 102b couples earth potential G, and the grid of switch 102b flows through the size of switch 102b according to size decision conducting state, nonconducting state or the electric current of voltage Vn.Therefore, the conducting state of

control switch

102a and 102b can be reached output voltage V 3 sizes of adjusting decision circuitry 102 thus.

One embodiment; Switching circuit 103 couples decision circuitry 102 and input voltage vin; And according to output voltage V 3 decide switching circuit 103 conducting state, nonconducting state or electric current flow through the size of switching circuit 103, and then can reach the effect of control switch circuit 103 action.For example, when switching circuit 103 conductings, electric current can be released into earth potential G via switching circuit 103.In the present embodiment, switching circuit 103 can be a N type metal oxide semiconductor field-effect transistor and realizes, but the present invention should be as limit.Another embodiment also can be implemented by the present existing or future semiconductor element that develops.

For the input voltage vin that electrostatic discharge protection circuit 100 can decision node N1 be received still is electrostatic potential V for the operating voltage Vdd that starts fast _ESD, therefore, please be simultaneously with reference to figure 2A; In the present invention one implements; When input voltage vin was the operating voltage Vdd that starts fast, input voltage vin was in Tr between the quick starting period, and meaning is that input voltage vin is in during the fast rise; Generally speaking Tr is less than 10 μ s, and the relational expression of voltage Vp,

resistance

101a and 101b meets following equation in fact:

V_{in} - Vp = V_{1} = \frac{Z_{1}}{Z_{1} + Z_{2}} \times V_{in} - - - (1)

Vdd - Vp = V_{1} = \frac{Z_{1}}{Z_{1} + Z_{2}} \times Vdd < V_{thp} - - - (2)

Wherein, Z1 and Z2 represent the equivalent impedance of

resistance

101a and 101b respectively, and Vdd is the operating voltage of input voltage vin, V _ThpBe the critical voltage (threshold voltage) of switch 102a, V1 is the conducting voltage of switch 102a; What specify is, at input voltage vin Tr between the quick starting period, because the input voltage vin rate of climb is very fast, makes that the voltage difference of electric capacity 101c can instantaneous variation, and the end of electric capacity 101c couples earth potential G, and therefore, voltage Vn levels off to zero.It is noted that after the Tr, the effect of electric capacity 101c promptly begins to take place between the quick starting period, therefore by finding that voltage Vp and voltage Vn begin slowly to rise among the 2A figure.

And please be simultaneously with reference to figure 2A; Fig. 2 A illustrates electrostatic discharge protection circuit 100 of the present invention when just starting (power on); Voltage analogous diagram under the input voltage vin fast rise situation can be understood input voltage vin, voltage Vp and voltage Vn three's relation by Fig. 2 A.

Dividing potential drop produces circuit 101 and receives input voltage vin; And export a voltage Vp and a voltage Vn according to input voltage vin; Wherein, when input voltage vin is in Tr between the quick starting period (for example: circuit just starts), via resistance value Z1 and the Z2 of design resistance 101a and resistance 101b; The transient voltage of voltage Vp and the formed conducting voltage V1 of operating voltage Vdd make switch 102a be in nonconducting state; Can understand by Fig. 2 A; Tt during a transient state; Promptly just start (t=0) during the stable state (comprising Tr between the quick starting period) from circuit, the transient voltage of voltage Vp and the formed conducting voltage V1 of operating voltage Vdd still make switch 102a be in nonconducting state.So, can understand the electrostatic discharge protection circuit 100 of present embodiment by above-mentioned; Under the zooming situation of input voltage vin, input voltage vin is during less than a default value, and the transient voltage of voltage Vp makes that switch 102a is a nonconducting state; Illustrate; In one implemented, operating voltage was 3.3V, so default value can be set at 3.3V (maybe can be set at a little more than 3.3V); When input voltage vin during smaller or equal to 3.3V, the transient voltage that dividing potential drop produces the voltage Vp that circuit 101 exported makes switch 102a be in nonconducting state.

In like manner, under the zooming situation of input voltage vin, input voltage vin is during greater than another default value; The transient voltage of voltage Vp makes that switch 102a is a conducting state, illustrates, in one implements; Operating voltage is 3.3V; Therefore default value can be set at 5V, and when input voltage vin during greater than 5V, the transient voltage that dividing potential drop produces the voltage Vp that circuit 101 exported makes switch 102a be in conducting state.

In addition, Tt during transient state, the transient voltage of voltage Vp and voltage Vn big or small unequal.For switching circuit 103 Tt during transient state is not switched on, be to have a preset relation between voltage Vp of the present invention, voltage Vn and the operating voltage Vdd, promptly the formed conducting voltage V1 of Vp and Vdd makes switch 102a be in nonconducting state.

Must note, when voltage Vin is operating voltage Vdd and does not have V _ESDDuring interference, the input voltage vin of electrostatic discharge protection circuit 100 is between the quick starting period among the Tr, can learn by aforementioned formula (2), Operating voltage Vdd will be because of impedance Z 1 dividing potential drop with Z2, and makes the critical voltage Vthp of the magnitude of voltage of conducting voltage V1 less than switch 102a; Certainly, because the influence of electric capacity 101c, before being in stable state to electrostatic discharge protection circuit 100 after the Tt between the starting period fast, voltage Vp rises gradually, so the magnitude of voltage of conducting voltage V1 is still less than the critical voltage Vthp of switch 102a.Therefore, switch 102a will be in non-conduction (Off) state, can avoid when the input voltage vin rate of climb near the speed of static discharge, cause switch 102a conducting and let switch circuit 103 error startings.Magnitude of voltage as for the conducting voltage V2 of node N3; Because of the zooming relation of input voltage vin (Vdd) causes electric capacity 101c stored charge speed slower; Make the voltage quasi position of conducting voltage V2 still be in low-voltage (leveling off to 0), then switch 102b is in non-conduction (Off) state.Because of

switch

102a and 102b all are in non-conduction (Off) state, so the time node Nj be suspension joint (floating), output voltage V 3 is in unknown state; Please refer to Fig. 2 B, above-mentioned output voltage V 3 is in unknown state, possibly cause switching circuit 103 conductings; Electrostatic discharge protection circuit 100 possibly produce a non-prospective current through switching circuit 103, but owing to voltage Vn (being conducting voltage V2), can slowly rise after the Tr between the starting period fast; As voltage Vn during greater than the critical voltage Vthn of switch 102b; Switch 102b is in conducting (On) state immediately, and this moment, output voltage V 3 was the accurate position of low-voltage, was in nonconducting state to guarantee switching circuit 103; And the unexpected current maxima than known electrostatic discharge protection circuit can reach more than the 400mA, and the unexpected current maxima of present embodiment is much smaller than 400mA, so unexpected electric current can decline to a great extent.And after the electrostatic discharge protection circuit 100 entering stable states, can understand by Fig. 2 A, the voltage quasi position of voltage Vp, Vn equates that with operating voltage Vdd switching circuit 103 is still kept nonconducting state.

When input voltage vin is electrostatic potential V _ESDThe time, and input voltage vin is in Tr during the fast rise, and electrostatic discharge protection circuit meets following equation in fact:

V_{ESD} - Vp = V_{1} = \frac{Z_{1}}{Z_{1} + Z_{2}} \times V_{ESD} > V_{thp} - - - (3)

Wherein, V _ESDThe magnitude of voltage that is produced when being expressed as static discharge.

Please be simultaneously with reference to figure 3A, Fig. 3 A illustrates electrostatic discharge protection circuit of the present invention, at electrostatic potential V _ESDBe introduced into the voltage analogous diagram under the situation.Fig. 3 A can understand input voltage vin, voltage Vp and voltage Vn three's relation.

When the situation generation of static discharge, input voltage vin is electrostatic potential V _ESDThe time, can learn by aforementioned formula (3),

Though electrostatic potential V _ESDStill by impedance Z 1 and Z2 dividing potential drop, but because electrostatic potential V _ESDMagnitude of voltage generally be much larger than operating voltage Vdd; Even so through dividing potential drop; The magnitude of voltage of the conducting voltage V1 that is caused by electrostatic potential VESD still can be greater than the critical voltage Vthp of switch 102a; So switch 102a will be in conducting (On) state, and switching circuit 103 is in conducting state, with release electrostatic voltage V _ESDThe electric current that is caused; What specify is, at electrostatic potential V _ESDAfter the Tr, electric current is through electric capacity 101c slightly owing to still have during the fast rise, and the voltage of electric capacity 101c can slightly rise, by finding among Fig. 3 A that voltage Vp and voltage Vn still can slowly rise, and move closer to input voltage vin; Among Fig. 3 A, the t2 time of being indicated is voltage Vp and the formed conducting voltage V1 of the electrostatic potential critical voltage Vthp less than switch 102a, and this moment, switching circuit 103 was in nonconducting state.

And the magnitude of voltage of the conducting voltage V2 of node N3, because of electrostatic potential V _ESDZooming relation causes electric capacity 101c stored charge speed slower, makes the voltage quasi position of conducting voltage V2 still be in low-voltage (leveling off to 0); Then switch 102b is in non-conduction (Off) state; What pay special attention to is that in the present embodiment, the RC time constant that

resistance

101a, 101b and electric capacity 101c are formed needs the time of origin greater than static discharge; Make switch 102b in the time of origin of static discharge, still be in nonconducting state.

Please again with reference to figure 3B, Fig. 3 B illustrates the current simulations figure of electrostatic discharge protection circuit 100 corresponding to Fig. 3 A.During conducting voltage V1 is greater than the critical voltage Vthp of switch 102a; Because switching circuit 103 is switched on, so produce a static discharge current (electric current shown in Fig. 3 B), it flows through switching circuit 103; Make electric current be released into earth potential G, avoid circuit because of electrostatic potential V via switching circuit 103 _ESDReceive permanent damage.

Note that by Fig. 3 A and can know at this, when electrostatic discharge protection circuit 100 is in stable state, electrostatic potential V _ESD, voltage Vp and voltage Vn voltage quasi position can level off to equal.

See also Fig. 4; Fig. 4 is that the dividing potential drop that electrostatic discharge protection circuit of the present invention is shown produces circuit in the sketch map of an embodiment, and as shown in Figure 4, electrostatic discharge protection circuit 200 is with the difference of electrostatic discharge protection circuit 100; Resistance 201a, 201b are realized by the P-type mos field-effect transistor respectively; The gate terminal of resistance 201a, 201b is coupled to earth potential G respectively, and the equiva lent impedance of resistance 201a, 201b is Z1, Z2, discloses so far; All the other operating principles are identical with electrostatic discharge protection circuit 100, and its detail operations of event is not given unnecessary details in this in addition for the sake of clarity.

See also Fig. 5, Fig. 5 is that the dividing potential drop that electrostatic discharge protection circuit of the present invention is shown produces circuit in the sketch map of an embodiment, and is as shown in Figure 5; Electrostatic discharge protection circuit 300 is with the difference of electrostatic discharge protection circuit 100;

Resistance

301a, 301b realize that by N type metal oxide semiconductor field-effect transistor the gate terminal of

resistance

301a, 301b is coupled to operating voltage Vdd respectively respectively, and the equiva lent impedance of

resistance

301a, 301b is Z1, Z2; Disclose so far; All the other operating principles are identical with electrostatic discharge protection circuit 100, for the sake of clarity, so do not give unnecessary details separately at this.

See also Fig. 6; Fig. 6 is the embodiment sketch map that electrostatic discharge protection circuit of the present invention is shown; As shown in Figure 6, electrostatic discharge protection circuit 400 is that with the difference of electrostatic discharge protection circuit 100 dividing potential drop produces circuit 401 and comprises a

resistance

401a, 401b, 401c and electric capacity 401d.

The end of resistance 401a is coupled to and couples node N1, other end series resistance 401b, and the two ends of resistance 401c are series resistance 401b and electric capacity 401d respectively.

And decision circuitry 402 couples the node N2 between

resistance

401a and 401b, and in addition, decision circuitry 402 also couples a node N3 between resistance 401b and the 401c, and node N2 and N3 difference output voltage V p and Vn.

Note that because

resistance

401a, 401b, 401c three are series connection then the voltage swing of its voltage Vp and Vn is to be determined by

resistance

401a, 401b, 401c, the resistance value that reaches electric capacity 401d through the dividing potential drop theorem respectively.

One embodiment, as shown in Figure 6, decision circuitry 402 can comprise

switch

402a and 402b, and node N2, the other end that the end of switch 402a couples dividing potential drop generation circuit 401 couple input voltage vin, and the other end couples switch 402b and forms a node Nj; The end of switch 402b couples that node N3, the other end that dividing potential drop produces circuit 401 couple node Nj and the other end couples an earth potential G.

Switch

402a and 402b receive voltage Vp and Vn respectively, and the voltage quasi position according to voltage Vp and Vn determine an output voltage V 3 so decision circuitry 402 can change because of the voltage swing of voltage Vp and Vn, also changes the voltage quasi position of output voltage V 3.

Among one embodiment, switch 402a is that a P-type mos field-effect transistor is realized, switch 402b is that a N type metal oxide semiconductor field-effect transistor is realized.Certainly, among another embodiment,

switch

402a, 402b are not limited to this, and it can be implemented by other present existing or future semiconductor element that develops.

As shown in Figure 6, the source electrode of switch 402a couples node N1 and receives input voltage vin, and the gate terminal of switch 402a flows through the size of switch 402a according to size decision conducting state, nonconducting state or the electric current of voltage Vp.

Accordingly, the drain electrode of switch 402b couples the drain electrode of switch 402a, and the source electrode of switch 402b couples earth potential G, and the grid of switch 402b flows through the size of switch 402b according to size decision conducting state, nonconducting state or the electric current of voltage Vn.Therefore, the conducting state of

control switch

402a and 402a thus can be reached the size of the output voltage V 3 of adjustment decision circuitry 402.

One embodiment; Switching circuit 403 couples decision circuitry 402 and input voltage vin; And decide conducting state, nonconducting state or the electric current of switching circuit 403 to flow through the size of switching circuit 403, and then can reach the effect of control switch circuit 403 actions according to output voltage V 3.For example, when switching circuit 403 conductings, electric current can be released into earth potential G via switching circuit 403.In the present embodiment, switching circuit 403 can be a N type metal oxide semiconductor field-effect transistor and realizes, but the present invention should be as limit.Another embodiment also can be implemented by the present existing or future semiconductor element that develops.

For the input voltage vin that electrostatic discharge protection circuit 400 can decision node N1 be received is for the operating voltage Vdd that starts fast or is electrostatic potential V _ESD, therefore, please be simultaneously with reference to figure 7A; In the present invention one implements; When input voltage vin was the operating voltage Vdd that starts fast, input voltage vin was in Tr between the quick starting period, and meaning is that input voltage vin is in during the fast rise; Generally speaking Tr is less than 10 μ s, and the relational expression of voltage Vp, Vn,

resistance

401a, 401b, 401c is as follows:

V_{in} - Vp = V_{1} = \frac{Z_{1}}{Z_{1} + Z_{2} + Z_{3}} \times V_{in} - - - (5)

V_{n} - 0 = V_{2} = \frac{Z_{3}}{Z_{1} + Z_{2} + Z_{3}} \times V_{in} - - - (6)

Vdd - Vp = V_{1} = \frac{Z_{1}}{Z_{1} + Z_{2} + Z 3} \times V_{dd} < V_{thp} - - - (7)

V_{n} - 0 = V_{2} = \frac{Z_{3}}{Z_{1} + Z_{2} + Z 3} \times V_{dd} > V_{thn} - - - (8)

Wherein, Z1, Z2, Z3 represent the equivalent impedance of

resistance

401a, 401b and 401c respectively, and Vdd is the operating voltage of input voltage vin, V _ThpBe the critical voltage (threshold voltage) of switch 402a, V _ThnCritical voltage for switch 402b; V1 is the conducting voltage of switch 402a, and V2 is the conducting voltage of switch 402b, wherein; Conducting voltage V1 is the voltage difference (being V1=Vin-Vp) of input voltage vin and voltage Vp, and conducting voltage V2 is the voltage difference (being V2=Vn-0) of voltage Vn and earth potential G.

What specify is; When input voltage vin is between the quick starting period Tr,, make that the voltage difference of electric capacity 401d can instantaneous variation because the input voltage vin rate of climb is very fast; Again because of voltage divider principle, so the voltage Vn that node N3 is exported levels off to 1V in one embodiment.It is noted that after the Tr, the effect of electric capacity 401d promptly begins to take place, therefore by finding among Fig. 7 A that voltage Vp and voltage Vn begin slowly to rise between the quick starting period.

Please be simultaneously with reference to figure 7A; Fig. 7 A illustrates electrostatic discharge protection circuit 400 of the present invention when just starting (power on); Voltage analogous diagram under the input voltage vin fast rise situation, Fig. 7 A can understand input voltage vin, voltage Vp and voltage Vn three's relation.

Dividing potential drop produces circuit 401 and receives input voltage vin; And export a voltage Vp and a voltage Vn according to input voltage vin; Wherein, as input voltage vin Tr (for example: when circuit just starts) between the quick starting period, via

design resistance

401a, 401b, the pairing resistance value Z1 of 401c, Z2, Z3; The transient voltage of voltage Vp and the formed conducting voltage V1 of operating voltage Vdd make switch 402a be in nonconducting state; Can understand by Fig. 7 A; Tt during a transient state; Promptly just start (t=0) during the stable state (comprise open fast during Tr) from circuit, the transient voltage of voltage Vp and the formed conducting voltage V1 of operating voltage Vdd still make switch 402a be in nonconducting state; In addition, Tt during transient state, the transient voltage of voltage Vp and voltage Vn big or small unequal.For switching circuit 403 Tt during transient state is not switched on, the design condition of voltage Vp of the present invention and voltage Vn is to have a preset relation, and promptly the formed conducting voltage V1 of Vp and Vdd makes switch 402a be in nonconducting state.

Must note, when voltage Vin is operating voltage Vdd and does not have electrostatic potential V _ESDDuring interference, the input voltage vin of electrostatic discharge protection circuit 400 is Tr between the quick starting period, can learn by aforementioned formula (7),

Operating voltage Vdd will be because of the dividing potential drop of impedance Z 1, Z2, Z3, and makes the magnitude of voltage of conducting voltage V1 can be less than the critical voltage V of switch 402a _ThpCertainly, because the influence of electric capacity 401d, before being in stable state to electrostatic discharge protection circuit 400 behind the Tt between the starting period fast, voltage Vp rises gradually, so the magnitude of voltage of conducting voltage V1 is still less than the critical voltage Vthp of switch 402a.Therefore, switch 402a will be in non-conduction (Off) state, can avoid causing switch 402a to be switched on, and letting switch circuit 403 by error starting when the input voltage vin rate of climb during near the speed of static discharge.

As for the magnitude of voltage of the conducting voltage V2 of node N3, by aforementioned formula (8),

The magnitude of voltage that can learn conducting voltage V2 is the critical voltage V that is designed to greater than switch 402b _Thn, in the present embodiment, switch 402b is in conducting state, and in other words, no matter after Tt during the transient state or electrostatic discharge protection circuit 400 were in stable state, switch 402b all was in conducting state.So the output voltage V 3 of node Nj is pulled to low-voltage; Can guarantee that switching circuit 403 Tr between the quick starting period is in nonconducting state; So switching circuit 403 can not avoided aforesaid embodiment by error starting, because of

switch

102a and 102b all are in non-conduction (Off) state; Making node Nj is suspension joint (floating) state, and output voltage V 3 is in unknown state.

Please refer to Fig. 7 B; Fig. 7 B illustrates the current simulations figure of electrostatic discharge protection circuit corresponding to Fig. 7 A, and when voltage rises too rapidly (when circuit just starts), unexpected electric current levels off to 0 (electric current shown in Fig. 7 B); Unexpected current maxima than known electrostatic discharge protection circuit possibly reach more than the 400mA; The about 1.4mA of unexpected current maxima of present embodiment so unexpected electric current declines to a great extent significantly, reduces short risk and takes place.

And after the electrostatic discharge protection circuit 400 entering stable states; Can be understood by Fig. 7 A, the voltage quasi position of voltage Vp, Vn equates that with operating voltage Vdd switch 402a still is in nonconducting state; This moment, switch 402b still was in conducting state; 3 of output voltage V still are the accurate position of low-voltage, and this moment, switching circuit 403 was not conducting, and then electrostatic discharge protection circuit 100 reverts to not starting state.

V_{ESD} - Vp = V_{1} = \frac{Z_{1}}{Z_{1} + Z_{2} + Z 3} \times V_{ESD} > V_{thp} - - - (9)

V_{n} - 0 = V_{2} = \frac{Z_{3}}{Z_{1} + Z_{2} + Z 3} \times V_{ESD} > V_{thn} - - - (10)

V wherein _ESDThe magnitude of voltage that is produced when being expressed as static discharge.

Note that by formula (8), (10) and can understand that no matter at the state of normal operating conditions or static discharge, the magnitude of voltage of conducting voltage V2 is the critical voltage V that is designed greater than switch 402b at this _Thn

Please be simultaneously with reference to figure 8A, Fig. 8 A illustrates electrostatic discharge protection circuit of the present invention, at electrostatic potential V _ESDBe introduced into the voltage analogous diagram under the situation.Fig. 8 A can understand input voltage vin, voltage Vp and voltage Vn three's relation.

Switching circuit 403 couples decision circuitry 402 and input voltage vin, and whether decides switching circuit 403 conductings according to output voltage V 3, when switching circuit 403 conductings, makes electric current be released into earth potential G via switching circuit 403.In the present embodiment, switching circuit 403 is that a N type metal oxide semiconductor field-effect transistor is realized, but the present invention should be as limit.

When the situation generation of static discharge, input voltage vin is electrostatic potential V _ESDThe time, can learn by aforementioned formula (9), Though electrostatic potential V _ESDStill by impedance Z 1, Z2, Z3 dividing potential drop, but because electrostatic potential V _ESDMagnitude of voltage generally be much larger than operating voltage Vdd; Even so through dividing potential drop; The magnitude of voltage of the conducting voltage V1 that is caused by electrostatic potential VESD can be greater than the critical voltage Vthp of switch 402a; So switch 402a will be in conducting (On) state, and switching circuit 403 is in conducting state, with release electrostatic voltage V _ESDThe electric current that is caused; What specify is, at electrostatic potential V _ESDAfter the Tr, electric current is through electric capacity 401d slightly owing to still have during the fast rise, and the voltage of electric capacity 401d can slightly rise, by finding that voltage Vp and voltage Vn still can slowly rise, and move closer to input voltage vin among the 8A figure; Among Fig. 8 A, the t2 time of being indicated is that voltage Vp and the formed conducting voltage V1 of electrostatic potential begin the critical voltage Vthp less than switch 402a, and this moment, switching circuit 403 was in nonconducting state.

And the magnitude of voltage of the conducting voltage V2 of node N3 can be learnt by aforementioned formula (10), and the magnitude of voltage of conducting voltage V2 can be greater than the critical voltage V of switch 402b _ThnSo switch 402b will be in conducting state.

Please again with reference to figure 8B, Fig. 8 B illustrates the current-mode graphoid of electrostatic discharge protection circuit 400 corresponding to Fig. 8 A.During conducting voltage V1 is greater than the critical voltage Vthp of switch 402a; Because switching circuit 403 is switched on, so produce an electric current (electric current shown in Fig. 8 B), electric current is to flow through switching circuit 403; Make electric current be released into earth potential G, avoid circuit because of electrostatic potential V via switching circuit 403 _ESDReceive permanent damage.

In addition, the pairing time constant of

resistance

401a, 401b, 401c and electric capacity 401d is greater than the static discharge time, and in other words, the RC time constant of being made up of

resistance

401a, 401b, 401c and electric capacity 401d needs the time of origin greater than static discharge.

Note that by Fig. 8 A and can know at this, when electrostatic discharge protection circuit 400 is in stable state, electrostatic potential V _ESD, voltage Vp and voltage Vn voltage quasi position can level off to equal.

In this enforcement; When the static discharge situation takes place;

Switch

402a and 402b are switched on simultaneously, and output voltage V 3 is that conduction impedance value by

switch

402a and 402b determines, in other words; Can suitably design the conduction impedance value of

switch

402a and 402b, make the magnitude of voltage of output voltage V 3 be enough to starting switch circuit 403.Because the equivalent impedance of switching circuit 403 is less than the equivalent impedance of decision circuitry 402, therefore, the big electric current that static discharge produced will be released into earth potential G through switching circuit 403, be damaged to avoid electronic component.

In sum, electrostatic discharge protection circuit of the present invention can be told static discharge or normal working voltage under voltage rises quick situation, thereby avoids the misoperation of electrostatic discharge protection circuit.

Claims

1. an electrostatic discharge protection circuit has a first node, and in order to receive an input voltage, said electrostatic discharge protection circuit comprises:

One dividing potential drop produces circuit; Couple said first node, said dividing potential drop produces circuit and exports one first voltage and one second voltage, wherein; During said input voltage was in a transient state, the transient voltage of the transient voltage of said first voltage and said second voltage was inequality;

One decision circuitry couples said dividing potential drop and produces circuit, receives said first voltage and said second voltage, and determines the voltage quasi position of an output voltage according to said first voltage, said second voltage; And

One switching circuit couples said decision circuitry, and determines said switching circuit conducting state according to the voltage quasi position of said output voltage.

2. electrostatic discharge protection circuit according to claim 1, wherein said dividing potential drop produce circuit and comprise:

One first resistance, an end couples said first node;

One second resistance, the other end of said first resistance of connecting, said decision circuitry is coupled to the Section Point between said second resistance and said first resistance; And

One electric capacity couples said second resistance, and said decision circuitry is coupled to one the 3rd node between said second resistance and said electric capacity.

3. electrostatic discharge protection circuit according to claim 2; Wherein, Be between a rising stage of said input voltage during the said transient state, the transient voltage of the transient voltage of said first voltage and said second voltage is by said input voltage, said first resistance and the decision of said second resistance.

4. electrostatic discharge protection circuit according to claim 2, wherein said decision circuitry comprises:

One first switch couples said Section Point, determines the whether conducting of said first switch according to said first voltage; And

One second switch, an end couple said the 3rd node, and the other end couples said first switch, and said second switch determines the whether conducting of said second switch according to said second voltage;

Wherein, whether the voltage quasi position of said output voltage decides according to said first switch and said second switch conducting.

5. electrostatic discharge protection circuit according to claim 4 is between a rising stage of said input voltage during the wherein said transient state.

6. electrostatic discharge protection circuit according to claim 5, wherein, when said input voltage was an operating voltage, the transient voltage of said first voltage made said first switch keep nonconducting state.

7. according to the electrostatic discharge protection circuit of claim 5 record, wherein, when said input voltage was an electrostatic potential, the transient voltage of said first voltage made said first switch keep conducting state.

8. electrostatic discharge protection circuit according to claim 4, wherein, when said input voltage was less than or equal to a default value, the transient voltage of said first voltage made that said first switch is a nonconducting state.

9. electrostatic discharge protection circuit according to claim 4, wherein, when said input voltage during greater than a default value, the transient voltage of said first voltage makes that said first switch is a conducting state.

10. electrostatic discharge protection circuit according to claim 5, wherein said first resistance have that one first resistance value Z1, said second resistance have one second resistance value Z2, said first switch has a critical voltage V _ThpWhen said input voltage was an operating voltage Vdd, the transient voltage of the said first voltage Vp met following equation in fact:

V_{dd} - V_{p} = \frac{Z_{1}}{Z_{1} + Z_{2}} \times V_{dd} < V_{thp} .

11. electrostatic discharge protection circuit according to claim 10, wherein working as said input voltage is an electrostatic potential V _ESDThe time, the transient voltage of the said first voltage Vp meets following equation in fact:

12. electrostatic discharge protection circuit according to claim 2, the pairing time constant of wherein said first resistance, said second resistance and said electric capacity is greater than the static discharge time.

13. electrostatic discharge protection circuit according to claim 1, wherein said dividing potential drop produce circuit and comprise:

One first resistance, an end is coupled to said first node;

One second resistance, the other end of said first resistance of connecting, said decision circuitry is coupled to the Section Point between said second resistance and said first resistance;

One the 3rd resistance, said second resistance of connecting, said decision circuitry is coupled to one the 3rd node between said second resistance and said the 3rd resistance; And

One electric capacity, one of which end are coupled to said second resistance, and the other end is coupled to an earth potential.

14. electrostatic discharge protection circuit according to claim 13; Wherein when said input voltage was between a rising stage, the transient voltage of the transient voltage of said first voltage and said second voltage was by said input voltage, said first resistance, said second resistance and the decision of said the 3rd resistance.

15. electrostatic discharge protection circuit according to claim 13, wherein said decision circuitry comprises:

16. electrostatic discharge protection circuit according to claim 15, wherein, when said input voltage was between a rising stage, the transient voltage of said second voltage makes said second switch keep conducting state.

17. electrostatic discharge protection circuit according to claim 15, wherein said first resistance has one first resistance value Z ₁, said second resistance has one second resistance value Z ₂, said the 3rd resistance has one the 3rd resistance value Z ₃, said first switch has a critical voltage V _Thp, said second switch has a critical voltage V _ThnWhen said input voltage is an operating voltage V _DdThe time, the said first voltage V _pTransient voltage, and the said second voltage V _nTransient voltage meet following equation:

V_{dd} - V_{p} = \frac{Z_{1}}{Z_{1} + Z_{2} + Z 3} \times V_{dd} < V_{thp}

With

V_{n} = \frac{Z_{3}}{Z_{1} {+ Z}_{2} + Z_{3}} \times V_{Dd} > V_{Thn} .

18. electrostatic discharge protection circuit according to claim 17 is when said input voltage is an electrostatic potential V _ESDThe time, wherein, the said first voltage V _pTransient voltage, and the said second voltage V _nTransient voltage meet following equation:

V_{dd} - V_{p} = \frac{Z_{1}}{Z_{1} + Z_{2} + Z_{3}} \times V_{ESD} < V_{thp}

With

V_{n} = \frac{Z_{3}}{Z_{1} {+ Z}_{2} + Z_{3}} \times V_{ESD} > V_{Thn} .

19. electrostatic discharge protection circuit according to claim 18; Wherein when said input voltage is an electrostatic potential; Said decision circuitry produces said output voltage according to the conduction impedance value of said first switch and said second switch, and said output voltage makes that said switching circuit is a conducting state.