CN100553143C - The N trap potential switching circuit - Google Patents

Abstract

The present invention relates to a kind of circuit based on N trap potential handoff technique, the compatible input and output of 3/5V of PMOS threshold voltage restriction in the time of can connecting big resistance pull-up resistor and thoroughly eliminate the switching of N trap potential, it comprises drawing-die piece and low level driver module on N trap potential handover module, N trap potential switching controls module, the micro-current source; Recommending under the output characteristic, circuit inside can provide on tens microamperes weak and draw ability; Opening Lou under the output characteristic, circuit can cut off the weak pull-up current source of inner microampere order automatically, prevent electric current from outside connect and draw power supply to pour in down a chimney into circuit work power, possess draw on weak, strong drop-down extensively adaptive capacity.

Description

The N trap potential switching circuit

Technical field

The present invention relates to a kind of circuit, belong to microelectric technique based on N trap potential handoff technique, the compatible input and output of 3/5V of PMOS threshold voltage restriction in the time of can connecting big resistance pull-up resistor and thoroughly eliminate the switching of N trap potential.

Background technology

In the application of integrated circuit, chip that is operated under certain low-voltage often needs to be operated in high-tension relatively chip and to be connected with one, for example a CPU who is operated under the 3.3V voltage needs to link to each other with a peripheral circuit that is operated under the 5.0V voltage, 3.3V the high level signal that produces of CPU be 3.3V, and the high level signal that 5.0V ancillary equipment produces is 5.0V, in order to realize line and (line or) signal, can link together their output signal, if do not add the words of any safeguard measure, clearly, the electric current of 5.0V power supply can pour in down a chimney the power supply into 3.3V; And when if the peripheral circuit pull-up resistor that connects is big resistance resistance, such as 100k Ω, find that the output of chip may produce vibration, as shown in Figure 2.Though produced some N trap potential handoff techniques energy head it offs now, the principle of these technology all is under the traditional solution that is based upon as shown in Figure 1 after all, there is following shortcoming in sort circuit:

(1) voltage on the PAD must satisfy:

V _PAD≥(V _DD+|V _THP|)

The N trap potential could be realized switching to normally on the higher outside of voltage and draw power supply.If PAD voltage is in:

V _DD≤V _PAD≤(V _DD+|V _THP|)

Because holding between the N trap of making PMOS from PAD has a PN junction, thus from PAD to continuing the N trap that a leakage current is arranged.

(2) under the situation of the so big pull-up resistor of external 100k Ω on the PAD, the PAD current potential can produce vibration.Before the N trap potential switched, after the electric weight on the wait PAD was put aside and satisfied N trap potential switching condition, the N trap potential began to switch.In the moment of switching, because the low-resistivity of M8, the PAD current potential is descended immediately and be tending towards near V _DDThe PAD current potential of this moment can not satisfy N trap potential switching condition, and M8 recovers to close.After M8 closed, the electric weight on the PAD restarted savings, and the PAD current potential can satisfy switching condition again then, so begin once more to switch.So repeatedly, the voltage on the PAD is easy to cause vibration, causes normally producing high level.

Summary of the invention

The purpose of this invention is to provide a kind of when output port voltage exceeds tens millivolts of chip operating voltages, still can realize the normal switching of N trap potential, and eliminated the oscillatory occurences that produces in the N trap potential handoff procedure, make the output port level rise to the outer commutation circuit of drawing supply voltage that connects at an easy rate.

For achieving the above object, N trap potential switching circuit of the present invention comprises drawing-die piece and low level driver module on N trap potential handover module, N trap potential switching controls module, the micro-current source, its principle as shown in Figure 3, wherein:

A) described N trap potential handover module is made up of N trap potential switching main body, anti-shake resistance 2 and two gating switches 4 and 5; Two PMOS that constitute N trap potential switching main body manage among P1 and the P2, and the source end of P1 connects power supply V _DDThe source end of P2 connects the output of this commutation circuit by anti-shake resistance 2, the drain terminal of the drain terminal of P1, substrate and P2, substrate are connected to each other and export the N trap potential together, the grid of P1 links to each other with an end of gating switch 4 and an end of gating switch 5 respectively, and the grid of P2 is connected to the output of described N trap potential switching controls module; The other end of gating switch 4 is connected to described N trap potential, and the gating end is connected to the output of described N trap potential switching controls module; The other end of gating switch 5 is connected to ground (GND), and the gating end is connected to the output of described N trap potential switching controls module;

B) described N trap potential switching controls module is made up of comparator and logic control element; An input of comparator is connected to chip power V _DD, another input is connected to the output of this commutation circuit, and the output of comparator is connected to the input of logic control element; Another input of logic control element is connected to the input of this commutation circuit, and the output of logic control element links to each other with the grid of P2 in the N trap potential handover module;

C) the drawing-die piece is made up of mirror current source, current sink I1, anti-shake resistance 1 and three gating switches 1,2 and 3 on the described micro-current source; The substrate of mirror current source is connected to described N trap potential; One end of gating switch 1 is connected on the bias level of mirror current source, and the other end is connected to described N trap potential, and the gating end is connected to the output of comparator in the described N trap potential switching controls module; One end of gating switch 2 is connected to the input of described mirror current source, and the other end is by current sink I1 ground connection, and the gating end is connected to the output of comparator in the described N trap potential switching controls module; One end of gating switch 3 is connected to the output of described mirror current source, and the other end is by the output of anti-shake resistance 1 this commutation circuit of connection, and the gating end is connected to the input of this commutation circuit;

D) described low level driver module is the device that low level output driving force can be provided, and its input links to each other with output with the input of this commutation circuit respectively with output.

N trap potential switching circuit of the present invention can utilize common P substrate and CMOS process to manufacture chip form, it can discern applied mode of operation automatically, and be correspondingly processed: recommending under the output characteristic, chip internal can provide on tens microamperes weak and draw ability; Opening Lou under the output characteristic, chip can cut off the weak pull-up current source of inner microampere order automatically, prevent electric current from outside connect and draw power supply (V _Pullup) pour in down a chimney into chip operation power supply (V _DD).Have the following advantages:

(1) thoroughly eradicates V _THPThe restriction of this threshold voltage.Because in common P substrate and CMOS process, V _THPValue be generally-0.7～-1.2V about, so the intrinsic condition of this technology tends to limit the application of these circuit.And N trap potential switching circuit of the present invention has thoroughly been eradicated this restrictive condition.

(2) under the characteristic of opening leakage, even the pull-up resistor of external 100k Ω, commutation circuit of the present invention also can guarantee to realize the normal switching of N trap potential, and dead-beat produces (as shown in Figure 5).

(3) under the characteristic of opening leakage, during the output high level, connect outward and draw real realization zero electric leakage of power supply.

Description of drawings

Fig. 1 is a prior art N trap potential switching circuit schematic diagram;

Fig. 2 is the shake waveform schematic diagram that is easy to generate in the prior art N trap potential handoff procedure;

Fig. 3 is a N trap potential switching circuit schematic diagram of the present invention;

Fig. 4 is a N trap potential switching circuit embodiment schematic diagram of the present invention;

Fig. 5 is the simulation waveform figure of N trap potential switching circuit of the present invention.

Embodiment

An embodiment of N trap potential switching circuit of the present invention as shown in Figure 4, it is made up of drawing-die piece and low level driver module on N trap potential handover module, N trap potential switching controls module, the micro-current source.

The drawing-die piece mainly produces the micro-current source of a weak driving force on the micro-current source, is generally tens microamperes.I1 in the module is the reference current that chip produces, and produces tens microamperes pull-up current after the mirror current source that M1, M2 constitute amplifies.M3 in the module is the PMOS switching tube, and M4 is the nmos switch pipe.As outside connect when drawing power supply, M3 opens, M4 closes.The purpose that M3 opens is being higher than V _DDThe N trap potential be sent to the grid of M1 and M2, can close built-in weak pull-up current source like this, change by connecting outward and draw power drives; While pours in down a chimney into V after can also preventing to connect outward and drawing power supply through R1, M5, M2 _DD, because the M5 of this moment is a conducting state.The reason that M4 closes also is in order to close weak pull-up current source, and it can also prevent inflow place after the N trap potential is through M3, M4, I1 simultaneously.M5 in the module is the PMOS switching tube, opens this metal-oxide-semiconductor when the output high level, when output low level, closes this metal-oxide-semiconductor.Anti-shake resistance when the R1 in the module switches for the N trap potential prevents that the PAD_OUT current potential from producing vibration.

N trap potential switching controls module main purpose is to produce N trap potential switch-over control signal.Module is by a return difference comparator and one or form.R3 among the figure is an esd protection resistance, and it doesn't matter with the function of control circuit.The behavior of comparator is: the level on PAD_OUT is higher than V _DDAdd a comparator return difference amount (V _HYS) time, comparator is output as low level; Level on PAD_OUT is lower than V _DDThe time, comparator is output as high level.In conjunction with OR circuit, this control module is handled three signal input states, produces a switch-over control signal:

(1) input CORE_IN=high level.It is low level that this state requires output PAD_OUT, so do not consider to export the level on the PAD_OUT under this state.Output N trap potential switch-over control signal is a high level, and promptly the N trap potential is V _DD

(2) input CORE_IN=low level, V _DD≤ V _{PAD_OUT}＜(V _DD+ V _HYS).Connecting to draw power supply or connect outward outside being equivalent to draws power supply not reach certain voltage request.Output N trap potential switch-over control signal is a high level, and promptly the N trap potential is V _DD

(3) input CORE_IN=low level, V _{PAD_OUT}〉=(V _DD+ V _HYS).Be equivalent to have outer connecting to draw power supply and it to reach certain voltage request.Output N trap potential switch-over control signal is a low level, and promptly the N trap potential switches to higher outer connecting and draws supply voltage.

N trap potential handover module is mainly used in and produces the N trap potential.It can choose V automatically according to the control signal of control module _DDConnect outward and draw higher one of voltage in the power supply as the N trap potential.Connecting outside preventing like this draws power supply to pour in down a chimney into V _DDM7, M8 constitute traditional N trap potential switching circuit structure.But their control mode is different.The no longer defective V that is connected to of the grid of M8 _DD, but be connected to the output of N trap potential switching controls module.When needing the N trap potential to switch to higher outer connecting when drawing power supply, control module is output as low level, has so just thoroughly eradicated traditional scheme and has connected at home and abroad and draw supply voltage to add one more than or equal to the chip operation supply voltage | V _THP| restrictive condition.The effect of M9 is analogous to M3, when the N trap potential switch to higher outer connect draw power supply after, by M9 the grid voltage of M7 also is changed to higher outer connecting and draws level.Otherwise the N trap potential can flow into V behind M7 _DDThe effect of M10 is to draw under the situation of power supply on outside higher not needing to switch to, and the grid of being put M7 by M10 is a low level, thereby the N trap potential is fixed as V _DDAnti-shake resistance when the R2 in the module switches for the N trap potential prevents that the PAD_OUT current potential produces vibration in N trap potential handoff procedure.

The low level driver module can provide low level output driving force.M6 is a low level output driver spare.If when chip internal required the output output low level, M6 was switched on, and makes output pull down to ground by force, provide low level output driving force.If when chip internal required output output high level, M6 was closed.

Draw power supply (V by outer the connecting that obtain that equivalent transformation can be rough _Pullup), external pull-up resistor (R _Pullup), current-limiting resistance (R ₂), chip operation power supply (V _DD), comparator return difference (V _HYS) have following relational expression between five:

$R_{\mathrm{pullup}}\&le;(\frac{V_{\mathrm{pullup}}-V_{\mathrm{DD}}}{V_{\mathrm{HYS}}}-1)\&times;\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="C20061014884500121.png"\; state="\{\{state\}\}">R</figure-callout>}2$

According to top inequality, we can be following hypothesis: V _HYS=25mV, R ₂=16k Ω.Set when these parameters of supposing can be by circuit design.

Work as R _Pullup=4.7k Ω.We can obtain following inequality: (V _Pullup-V _DD) 〉=32.34mV.This formula means as long as outer connecting draws the working power voltage 32.34mV of supply voltage more than or equal to chip, N trap potential just can normally switch to draw power supply on external.

Work as R _Pullup=100k Ω.We can obtain following inequality: (V _Pullup-V _DD) 〉=181.25mV.Even this formula means external pull-up resistor and arrives 100k Ω greatly, but as long as outer connecting draw the working power voltage 181.25mV of supply voltage more than or equal to chip, N trap potential just can normally switch to draw power supply on external.

This shows that the feature and advantage of N trap potential switching circuit of the present invention are apparent.

Claims (1)

1. N trap potential switching circuit, it is characterized in that: it comprises drawing-die piece and low level driver module on N trap potential handover module, N trap potential switching controls module, the micro-current source, wherein:

A) described N trap potential handover module is made up of N trap potential switching main body, the second anti-shake resistance, the 4th gating switch and the 5th gating switch; The N trap potential switches main body and is made of PMOS pipe and the 2nd PMOS pipe, and the source end of a PMOS pipe connects power supply V _DDThe source end of the 2nd PMOS pipe connects the output of this commutation circuit by the second anti-shake resistance, drain terminal, the substrate of the drain terminal of the one PMOS pipe, substrate and the 2nd PMOS pipe links together and exports the N trap potential, the grid of the one PMOS pipe links to each other with an end of the 4th gating switch and an end of the 5th gating switch respectively, and the grid of the 2nd PMOS pipe is connected to the output of described N trap potential switching controls module; The other end of the 4th gating switch is connected to described N trap potential, and the gating end is connected to the output of described N trap potential switching controls module; The other end ground connection of the 5th gating switch, gating end are connected to the output of described N trap potential switching controls module;

B) described N trap potential switching controls module is made up of comparator and logic control element; An input of comparator is connected to chip power V _DD, another input is connected to the output of this commutation circuit, and the output of comparator is connected to the input of logic control element; Another input of logic control element is connected to the input of this commutation circuit, and the output of logic control element links to each other with gating end, the gating end of the 5th gating switch and the grid of the 2nd PMOS pipe of the 4th gating switch in the N trap potential handover module;

C) the drawing-die piece is made up of mirror current source, current sink, the first anti-shake resistance, first gating switch, second gating switch and the 3rd gating switch on the described micro-current source; The substrate of mirror current source is connected to described N trap potential; One end of first gating switch is connected on the bias level of mirror current source, and the other end is connected to described N trap potential, and the gating end is connected to the output of comparator in the described N trap potential switching controls module; One end of second gating switch is connected to the input of described mirror current source, and the other end is by current sink ground connection, and the gating end is connected to the output of comparator in the described N trap potential switching controls module; One end of the 3rd gating switch is connected to the output of described mirror current source, and the other end connects the output of this commutation circuit by the first anti-shake resistance, and the gating end is connected to the input of this commutation circuit;

D) described low level driver module is the device with low level fan-out capability, and its input links to each other with output with the input of this commutation circuit respectively with output.

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