JPH0955469A - Leakage current compensation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a leakage current induced in a compensating diode equal to that induced in a parasitic diode in intensity and properties by a method wherein a specific amount of current is extracted from each end of a resistor device respectively, and a leakage current and a voltage drop in the resistor device are compensated. SOLUTION: The one terminal a of a resistor device R is connected to a circuit 20, and the other terminal b of the resistor device R is connected to a circuit 30. The parasitic diode D of the resistor device R is formed between an N-type region connected to a power supply VDD and a P-type region which forms the resistor device R. Furthermore, two currents, one is as large as n, and the other is as large as m [O<n, m, n+m ≈ leakage current], are extracted from the ends a and b of the resistor device R or I1 and I2 as large as n and m respectively are fed to a current Miller circuit 10 from the ends a and b of the resistor device R to compensate a leakage current IL and a voltage drop in the resistor device R. By this setup, the leakage current IC of a compensating diode DC can be set equal in intensity and properties to the leakage current IL of the parasitic diode D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention compensates a reverse leakage current of a resistance element having a parasitic diode formed in an integrated circuit (IC, LSI) in which leakage current becomes a problem during high temperature operation. Leakage current compensation circuit for

[0002]

2. Description of the Related Art FIG. 4 shows a structure of a general resistance element formed in a semiconductor integrated circuit. For example, as shown in FIG. 4A, the resistance element has a p-type in the n-type region.
It is general to form a region of e to form a resistor R having two terminals a and b. In this case, the n-type region is connected to the highest potential power supply VDD, and the p-type region is used such that a potential equal to or lower than the power supply VDD is applied. However, the p-type resistance element portion and VDD
A parasitic diode D exists between the terminal and the terminal (Fig. 4 (b)).
reference).

Since the parasitic diode D is normally placed in a zero or reverse bias state, basically no current flows there. However, a slight reverse leakage current flows through the parasitic diode D in the reverse bias state. Therefore, as shown in FIG. 5, the current flowing through the resistance between the terminals ab gradually increases (decreases) from the terminal a to the terminal b due to the leak current.

That is, assuming that the current flowing into the terminal a is I0, the current flowing out from the terminal b increases by IL which is the sum of the leak currents and becomes (I0 + IL). The increase in current for the leak current can be ignored in I0 >> IL, but the reverse leak current IL can be ignored because the leak current IL rapidly increases as the environmental temperature rises. Disappear.

Conventionally, as a countermeasure against such leakage current,
A circuit as shown in FIG. 6 is known. In this circuit,
A compensating diode DC for flowing a compensating current I0 having substantially the same value as the reverse leak current IL of the parasitic diode D is provided to compensate for the leak current.

Specifically, for a resistance element R having a parasitic diode D formed between a predetermined circuit 1 and circuit 2,
One terminal of the compensating diode DC is connected to the terminal b or the terminal a of the resistance element R, and the other terminal of the compensating diode DC is connected to the lowest potential power source VSS (for example, a ground potential power source).

Then, the power source V is supplied through the parasitic diode D.
A current equal to the leak current IL flowing from DD to the resistance element R is flown from the terminal b of the resistance element R to the power supply VSS via the compensation diode DC. By doing so, the current I0 flowing into the terminal a and the current I1 flowing through the resistance element R and flowing out of the terminal b become equal (I1 = I0), and the influence of the leak current can be eliminated.

Further, in order to compensate for the leak current with higher accuracy, the applicant of the present application has proposed a configuration as shown in Japanese Patent Application No. 147477 / 7-147. This has exactly the same structure as the parasitic diode, as shown in FIG.
This is a configuration in which the compensation diode DC connected to the current mirror circuit 20 and the current mirror circuit 20 are combined.

In this configuration, the input side transistor of the current mirror circuit 20 is connected to both ends of the compensation resistor RC having the compensation diode DC connected to the power supply VDD, and the current is supplied to the terminal b of the resistance element R to be compensated. The output side transistor of the mirror circuit 20 is connected.
Therefore, the compensation current IC0 flowing from the compensation diode DC into the resistance element RC is supplied to the input side transistor of the current mirror circuit 20 as an input current (= IC0),
In response to this, a current IC1 equal to the compensation current IC0 is drawn as an output current I1 from the terminal b to the output transistor of the current mirror circuit 20.

In the p-type region, n-type is added.
forming a region e, and having a resistance element R having two terminals a and b
In general, the p-type region is connected to the power supply VSS, and the n-type region is connected to the power supply VS.
Since a potential of S or more is applied, the direction of the leak current due to the parasitic diode D is opposite to the above direction,
That is, from the resistance element R to the power source VS via the parasitic diode D.
The direction is toward S, but it can be considered in exactly the same way.

[0011]

As described above,
If the configuration as shown in FIGS. 6 and 7 is used, the leakage current can be compensated by the parasitic diode, but the voltage drop between the terminals ab of the resistance element R due to the leakage current cannot be compensated. There was a problem.

That is, in the resistance element R having the parasitic diode D, a leak current is added (or extracted) to the current that should originally flow. Therefore, the current actually flowing in the resistance element R is different from the current that should originally flow, and the voltage drop originally generated in the resistance element R changes.

The present invention has been made for the purpose of solving this problem, and a leak current compensating circuit capable of compensating not only for the leak current but also for the voltage drop between the terminals ab of the resistance element R. Is intended to provide.

[0014]

The structure of the present invention and its operation / effect will be described below.

First, as shown in FIG. 8, consider a resistance element having two terminals a and b, the length between the terminals ab is L, the total leak current is IL, and the resistance value is R. Here,
It is assumed that the material of the resistance element is homogeneous and that the leak current has a uniform leak current density in the range from the terminals a to b.

A minute distance from the terminal a to x is dx
And the minute resistance component and minute voltage drop in the region of this minute distance dx are dr and dv, respectively. Further, when the current flowing into the terminal a is I0 and the current at the distance x from the terminal a is I (x), it can be expressed by the following equation.

[0017]

[Formula 1] dv = dr × I (x) ···· (1)

[Equation 2]

(Equation 3) Here, substituting equations (2) and (3) into equation (1),

(Equation 4) Then, integrating both sides yields the following.

[0018]

(Equation 5)

(Equation 6)

(Equation 7) Originally, the voltage drop Vab0 in the resistance element R when there is no leakage current is

## EQU00008 ## Vab0 = R.multidot.I0 ... (8) Therefore, due to the leakage current (R · IL / 2)
An additional voltage drop will occur.

Therefore, in the leak current compensating circuit according to the first configuration of the present invention, n and n are respectively applied from both ends of the resistance element.
m [0 <n, m, (n + m) is approximately equal to (leakage current)] is drawn, or the currents of n and m are supplied to both ends of the resistance element, respectively. The leakage current and voltage drop in the device are to be compensated.

For example, when n and m are set to ½ of the leak currents and currents of IL / 2 and IL / 2 are drawn from the terminal a and the terminal b of the resistance element, the voltage drop Vab between the terminals ab is , Is as follows.

[0021]

[Equation 9] The output current I1 from the terminal b is expressed by the following equation.

[0022]

(Equation 10) As is clear from the above formulas (9) and (10), the terminal ab
The voltage Vab between them and the current I1 flowing out from the terminal b of the resistor R
Is not affected by leakage current. Thus, both the voltage and the current can be compensated for in the configuration of the present invention.

Next, in the second configuration of the present invention, a current having a magnitude equal to the leak current of the parasitic diode is drawn from an intermediate terminal provided near the middle of the resistance element, or a current having a magnitude equal to the leak current at the intermediate terminal. Is supplied to compensate the leak current and voltage drop in the resistance element.

For example, when the intermediate terminal C is provided near the middle of the terminal ab of the resistance element R and the current of IL is drawn from this terminal C, the voltage drop Vab between the terminals ab is as follows.

[0025]

[Equation 11] Regarding the current,

## EQU12 ## I1 = I0-IL + IL = I0 (12)

As is clear from the above results, both the voltage and the current in the resistance element R can be compensated by causing the same current as the leak current to flow out from the intermediate terminal C of the resistance element R.

Further, in the leak current compensating circuit in which the third constitution of the present invention is added to the above constitution, compensation for generating a current equal to the leak current or half the leak current is generated. The diode is connected to the same first power supply as the parasitic diode of the resistance element. Then, a current mirror circuit that uses the compensation current flowing from the compensation diode as an input current extracts an output current corresponding to the input current from both ends or an intermediate terminal of the resistance element or supplies the output current to both ends or an intermediate terminal of the resistance element.

When a current having a magnitude of half the leak current is drawn or supplied from both terminals of the resistance element, the current mirror circuit includes an input side transistor to which a compensation current is input and a resistor. It has a plurality of output side transistors which are respectively connected to two terminals of the element and which draws or supplies an output current having a magnitude of 1/2 of the leakage current.

By adopting the third structure as described above, it becomes possible to form the compensation diode in the same structure (shape, area, perimeter, impurity concentration, etc.) as the parasitic diode in the same manufacturing process. The leakage current generated in the compensation diode can be made to have the same magnitude and characteristics as the leakage current generated in the parasitic diode.

Therefore, as compared with the conventional method, the leakage current can be compensated with higher accuracy. Further, stable leakage current compensation can be realized even with variations in the manufacturing process.

The magnitude of the compensation current obtained from the compensation diode is 1 / N (N is N) of the leakage current of the parasitic diode.
> 1) and the ratio of the magnitude of the input current to the output current of the current mirror circuit is set to 2 / N or 1 / N. As a result, the area occupied by the compensation diode can be reduced to about 1 / N, and in the case of N >> 1, higher integration can be achieved as compared with the conventional method.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

However, in the resistance element shown below, a p-type region is formed in the n-type region shown in FIG.
An example will be described in which the p-type region is used as a resistance element and the n-type region is connected to the power supply VDD. In this configuration, n-type and p-type are used.
It is assumed that a parasitic diode exists at the boundary of e and the leakage current density of this parasitic diode is uniform.

(Embodiment 1) FIG. 1 shows a leakage current compensation circuit according to Embodiment 1 of the present invention.

In FIG. 1, the terminal a of the resistance element R is connected to the circuit 20, and the terminal b is connected to the circuit 30.
The parasitic diode D of the resistance element R is connected to the power source VDD.
Is formed between the n-type region and the p-type region forming the resistance element R. For this reason,
Some reverse voltage is applied to the parasitic diode D,
The leak current IL flows through the parasitic diode D.

Therefore, in the present embodiment, this leakage current I
In order to compensate L, a compensation diode DC and a 1-input / 2-output current mirror circuit 10 are provided. Here, the compensation diode DC has the same pn as the parasitic diode D.
Junction structure (same shape, area, perimeter, impurity concentration, etc.)
N-typ to the same power supply VDD as the power supply VDD to which the parasitic diode D is connected.
The e region (cathode) is connected.

More specifically, this compensation diode DC
When a resistor RC exactly the same as the resistor element R is manufactured,
This is a diode using a parasitic diode formed in this resistor RC.

The current mirror circuit 10 is a basic current mirror circuit composed of three nMOS transistors MM0, MM1, MM2 having a [channel width / channel length] of 2: 1: 1. Transistors MM1 and MM are used as input side transistors.
2 respectively function as output side transistors.
Then, from the compensation diode DC to the input side transistor M
The ratio of the magnitude of the input current I0 supplied to M0 and the magnitude of the output currents I1 and I2 supplied by the output side transistors MM1 and MM2 is set to 2: 1: 1. The terminals a and b of the resistance element R are connected to the output terminals (output side transistors MM1 and MM2) of the current mirror circuit 10, respectively.

As described above, the compensating diode DC has the same structure as the parasitic diode D of the resistance element R, and generates a reverse current having the same magnitude as the leak current IL of the parasitic diode D, that is, a compensating current. To do. The compensation current is the input current I0 of the current mirror circuit 10. Therefore, the two output currents I flowing through the respective output side transistors MM1 and MM2 of the current mirror circuit 10
The size of 1, I2 is

(Equation 13) Becomes

When the compensation diode DC flows the same amount of compensation current as the leakage current IL of the parasitic diode D, the current mirror circuit 10 leaks from the terminals a and b of the resistance element R accordingly. Current IL 2
The currents I1 and I2 having a magnitude of one-half are extracted. Therefore,
When I1 and I2 are summed, a current having the same magnitude as the leak current IL flowing into the resistance element R is extracted. As a result, the current I20 flowing from the circuit 20 to the terminal a of the resistance element R and the current I30 flowing from the terminal b of the resistance R to the circuit 30 become equal and are not affected by the leak current IL. In this way, by using the reverse leakage current of the compensating diodes having exactly the same structure as the compensation current, it is possible to highly accurately compensate the leakage current.

Further, the voltage drop Vab between the terminals ab is
From equation (7)

[Equation 14] Therefore, the original voltage drop Vab in the resistance element R can be obtained without being affected by the leak current.

From the above, it can be seen that both the leakage current and the voltage drop due to this leakage current are compensated for in this embodiment.

Further, the current drawn from the terminals a and b of the resistance element R is not limited to one half of the leak current IL, but may be currents of n and m. The values of n and m are (0 <n, m) and (n + m) is the leakage current I.
It suffices that L is substantially equal, and its specific value can be set with more accuracy by setting the leak current IL flowing into the resistance element R in accordance with the bias, for example, when the current density is biased. The voltage drop due to the leakage current can be compensated.

In the embodiment, the compensation diode DC
A parasitic diode formed in the resistor RC having exactly the same structure as the resistor element R was used as. However, the configuration of the compensation diode DC is not limited to this. For example, the reverse leakage current of the compensation diode DC may be set to 1 / N, that is, IL / N. In this case, the compensation diode DC
Corresponding to the compensation current IL / N of each of the transistors MM0, MM1 and M of the current mirror circuit 10 having one input and two outputs.
The ratio of the magnitude of the current flowing through M2, that is, the ratio of the input current to the output current may be set to 2 to N to N.

Further, the current mirror circuit 10 is not limited to the circuit system shown in FIG. That is, as shown in FIG. 2, any circuit may be used as long as it can arbitrarily set the ratio of the magnitudes of the input current I0 and the output currents I1 and I2.
It suffices that a current set to an arbitrary value (for example, 1/2) with respect to the leak current flowing from the compensation diode DC to the compensation diode DC can be discharged from the terminals a and b of the resistance element R to the power supply VSS.

(Second Embodiment) FIG. 3 shows a leakage current compensating circuit according to a second embodiment of the present invention. In the figure, the terminal a of the resistance element R is connected to the circuit 20, and the terminal b is connected to the circuit 30. In addition, n− of the parasitic diode D
A power supply VDD is connected to the type region (cathode side), and like the first embodiment, a reverse voltage is applied to the parasitic diode D, and a reverse leakage current IL flows.

Therefore, in the present embodiment, in order to compensate for the leak current IL, an intermediate terminal c is provided near the middle of the terminals a and b of the resistance element R, and the leak current IL flowing from the intermediate terminal c to the parasitic diode D. It is configured to draw the same amount of current as.

Specifically, a compensation diode DC and a one-input one-output current mirror circuit 12 are provided so that the reverse current (compensation current) flowing through the compensation diode DC becomes an input current to the current mirror circuit 12. It is connected to the. The output terminal of the current mirror circuit 12 is connected to the intermediate terminal c of the resistance element R.

Here, the compensating diode DC is a diode having the same pn junction structure (same shape, area, perimeter, impurity concentration, etc.) as the parasitic diode D, as in the first embodiment.

The current mirror circuit 12 is a basic current mirror circuit, and uses two nMOS transistors having the same size as the input side transistor MM10 and the output side transistor MM11, and the input current I0 and the output current I1. Are equal in size.

As described above, since the compensation diode DC has the same structure as the parasitic diode D of the resistance element R, the leak current IL of the parasitic diode D is the reverse current of the same magnitude and is supplied as the compensation current. . This compensation current is applied to the input side transistor MM10 of the current mirror circuit 12.
Is supplied to the output side transistor MM11 of the current mirror circuit 12 as the input current I0.
The magnitude of the current that flows out to, that is, the magnitude of the output current I1, is

(15) I1 = I0 = IC = IL (15)

With the above configuration, the current mirror circuit 1
Therefore, a current having the same magnitude as the leak current IL flowing into the resistance element R is supplied from the intermediate terminal c of the resistance element R to the power supply VSS.
Is pulled toward. As a result, the current I20 flowing from the circuit 20 to the terminal a of the resistance element R and the current I30 flowing from the terminal b of the resistance element R to the circuit 30 become equal and are not affected by the leak current IL. As described above, according to the present embodiment as well, it is possible to highly accurately compensate the leak current by using the reverse current of the compensating diode having exactly the same structure.

Further, the voltage drop [Vab] across the terminals ab
Is the sum of the voltage drop [Vac] between the terminals ac and the voltage drop [Vcb] between the terminals cb, as shown in the following equation (16).

[0054]

(Equation 16) Therefore, the original voltage drop [Vab] that is not affected by the leak current is obtained, and the voltage drop caused by the leak current IL is also compensated.

As described above, according to the configuration of this embodiment,
Both the leak current and the voltage drop caused by the leak current can be compensated.

In this embodiment, as the compensation diode DC, the parasitic diode having the resistance RC having the same structure as the resistance element R is used, but the method of manufacturing the compensation diode DC is not limited to this. For example, as in the first embodiment, the reverse current of the compensating diode can be set to 1 / N, that is, IL / N. In this case, it is preferable to set the ratio of the input current to the output current of the 1-input 1-output current mirror circuit 10 to 1-N.

In the above two embodiments, n-type is used.
The resistance element manufactured by forming the p-type region in the region of 1 has been described as an example. However, if the resistance element is pt
When the n-type region is formed in the ype region, the direction of the leak current flowing through the parasitic diode is reversed and the leak current flows out from the resistance element. However, similar to the above embodiment. The leakage current can be compensated by thinking. That is, in the configuration of the first embodiment, the polarity of each transistor, the diode, the transistor, etc., and the power supply VS
By changing the connection relationship between S and VDD, the terminal a of the resistance element R,
It may be configured to supply a current of IL / 2 to each of b. On the other hand, in the configuration of the second embodiment, similarly, a current having the same magnitude as IL may be supplied to the intermediate terminal c of the resistance element R.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a leak current compensation circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation of the circuit 10 of FIG.

FIG. 3 is a diagram showing a configuration of a leak current compensation circuit according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a resistance element using junction separation in an integrated circuit.

5 is a diagram showing a leak current generation state in the resistance element of FIG. 4 and an equivalent circuit thereof.

FIG. 6 is a diagram showing a conventional compensating circuit for compensating a leak current of a resistance element.

FIG. 7 is a diagram showing a leakage current compensation circuit according to a related technique of the present invention.

FIG. 8 is a diagram for explaining the influence of a leak current on a resistance element.

[Explanation of symbols]

 10, 12 Current mirror circuit.

Claims (7)

[Claims] 1. A leak current compensating circuit for compensating a leak current in the reverse direction of a parasitic diode existing in a resistance element constituting an integrated circuit, wherein n and m [0 <n, m are provided from both ends of the resistance element, respectively. ,
(N + m) is approximately equal to the leak current], or currents of the magnitudes n and m are supplied to both ends of the resistance element to compensate for the leak current and voltage drop in the resistance element. A leak current compensating circuit characterized by: 2. A leak current compensating circuit for compensating for a reverse leak current of a parasitic diode existing in a resistance element which constitutes an integrated circuit, wherein the leakage current of the parasitic diode is divided into two parts from both ends of the resistance element. 1 is drawn out, or a current that is half the leak current is supplied to both ends of the resistance element to compensate the leak current and voltage drop in the resistance element. Leakage current compensation circuit. 3. A leak current compensating circuit for compensating for a reverse leak current of a parasitic diode existing in a resistance element forming an integrated circuit, wherein the parasitic diode is provided from an intermediate terminal provided near the middle of the resistance element. Of the leak current, or a current of the same magnitude as the leak current is supplied to the intermediate terminal to compensate a leak current and a voltage drop in the resistance element. Compensation circuit. 4. The leak current compensating circuit according to claim 1, wherein the leak current compensating circuit is connected to the same power source as the power source to which the parasitic diode is connected, and compensates for the reverse leak current. A compensating diode that flows as a current, and a current mirror circuit that uses the compensating current flowing through the compensating diode as an input current, and draw an output current of the current mirror circuit from both ends of the resistance element or the intermediate terminal, or A leak current compensating circuit for supplying to both ends or the intermediate terminal of the resistance element to compensate for a leak current and a voltage drop of the resistance element. 5. The leakage current compensating circuit according to claim 4, wherein the current mirror circuit is connected to an input side transistor to which the compensating current is input and to both ends of the resistance element, respectively.
A plurality of output-side transistors that draw an output current of the magnitude of or supply to both ends of the resistance element. 6. The leakage current compensating circuit according to claim 5, wherein the current mirror circuit is connected to an input side transistor to which the compensating current is input and both ends of the resistance element, respectively. A leakage current compensating circuit, comprising: a plurality of output side transistors that draw an output current of ½ or supply to both ends of the resistance element. 7. The leakage current compensating circuit according to claim 4, wherein the magnitude of the compensating current obtained from the compensating diode is 1 / N (N is N Number of N> 1)
And the ratio of the magnitude of the input current to the output current of the current mirror circuit is set to 2 to N or 1 to N.