JP4337770B2 - Voltage comparison circuit and threshold voltage correction method thereof - Google Patents

Description

  The present invention relates to a high-speed and high-accuracy voltage comparison circuit, and a threshold voltage correction method for a voltage comparison circuit that can be performed without requiring a special process.

A CMOS inverter composed of an NMOS transistor and a PMOS transistor has a simple circuit configuration and can operate at high speed, and thus may be used as a voltage comparison circuit.
However, the CMOS inverter has a characteristic that the threshold voltage fluctuates greatly due to manufacturing variations such as the gate length and channel dose of the NMOS transistor and the PMOS transistor. Therefore, a high-accuracy voltage comparison is required as it is. This is a voltage comparison circuit that is unsuitable for a circuit.

Therefore, such a variation in threshold voltage is suppressed by cutting a predetermined portion of the circuit by laser trimming, and is set to an appropriate voltage. For example, in the technique disclosed in Patent Document 1, the reference voltage is set to an appropriate value by cutting the fuse of the reference voltage generation circuit with a laser.
Further, in Patent Document 2, a PMOS transistor of a CMOS inverter used as a comparator is added with a threshold variable transistor group and a switch group, and each of the threshold variable transistors is turned on and off, whereby the PMOS transistor in the CMOS inverter is switched. A technique is shown in which the threshold voltage can be adjusted by changing the effective size (gate width W).
JP-A-8-17190 Japanese Patent Laid-Open No. 5-199116

However, as described above, in order to set the reference voltage by adjusting the circuit by laser trimming, it is necessary to go through a special process such as laser trimming, and the manufacturing process of the IC chip constituting the reference voltage generation circuit Was complicated.
Further, in the technique of Patent Document 2 in which a CMOS inverter having a configuration in which a threshold variable transistor group and a switch group are added to a PMOS transistor is described, if the added threshold variable transistor group is controlled to be turned on / off, a desired value can be obtained. The actual control content, such as whether the threshold value can be obtained, has not been materialized, and the threshold value cannot actually be set with high accuracy.
Therefore, in the present invention, a correction transistor group is provided in the CMOS inverter, and based on the output of the CMOS inverter, the threshold voltage and the reference voltage are sequentially compared so that the threshold voltage approaches the reference voltage. A voltage comparison circuit configured to perform on / off control of a transistor group and a threshold voltage correction method thereof are provided.

The voltage comparison circuit and the threshold voltage correction method for solving the above problems have the following characteristics.
That is, as described in claim 1, voltage comparison means including at least a pair of complementary transistors that outputs an analog input as a comparator according to a predetermined threshold value;
A reference voltage generating means for generating a reference voltage;
An external input signal that is a comparison target signal and the reference voltage are selectively switched to be input in parallel to at least one of the complementary transistors, and an input signal switching unit that inputs the analog input to the voltage comparison unit, A voltage comparison circuit comprising a correction transistor group including a plurality of correction transistors that are turned on and off by the switching means, and correction switching control means for controlling the switching means of each of the correction transistors. When the reference voltage is connected to the input terminal of the voltage comparison means by the input signal switching means, the correction switching control means is responsive to the output signal from the voltage comparison means and the reference voltage and voltage comparison means. Based on the comparison result of the successive approximation unit and the successive approximation unit. And a switching correction unit for performing on-off switching of the switching means of each correcting transistor.
As a result, the threshold voltage of the voltage comparison unit and the reference voltage from the reference voltage generation unit can be made equal to the range of the potential difference generated by the quantization error.
Therefore, it is possible to correct the deviation of the threshold voltage due to manufacturing variations of the voltage comparison means with high accuracy, and the voltage comparison means can perform a highly accurate and reliable voltage comparison operation.
Further, the correction by the successive comparison does not require a special trimming process such as a non-volatile memory, a laser cut, or a zap, so that the correction work can be simplified.
Furthermore, by configuring the voltage comparison means of this voltage comparison circuit with a CMOS inverter, voltage comparison can be performed at high speed (for example, about several ns), and correction processing can be performed quickly.

According to a second aspect of the present invention, the analog input is compared with a voltage comparison means including at least a pair of complementary transistors that outputs a comparator according to a predetermined threshold, and a reference voltage generation means that generates a reference voltage. An input signal switching means for selectively switching an external input signal as a target signal and the reference voltage to be input to the voltage comparison means as an analog input, and at least one of the complementary transistors is connected in parallel. In a voltage comparison circuit comprising a correction transistor group having a plurality of correction transistors whose control terminals are switched on and off by means, and a correction switching control means for controlling the switching means of each correction transistor. The reference voltage is connected to the input terminal of the voltage comparison means by the input signal switching means. When and, by the correction switching control unit,
In accordance with the output signal of the voltage comparison means, the threshold voltage of the voltage comparison means and the reference voltage are sequentially compared, and on the basis of the result of the successive comparison, each switching means of the correction transistor group is turned on / off. Switching is performed to correct the threshold voltage of the voltage comparison means.
As a result, the threshold voltage of the voltage comparison unit and the reference voltage from the reference voltage generation unit can be made equal to the range of the potential difference generated by the quantization error.
Therefore, it is possible to correct the deviation of the threshold voltage due to manufacturing variations of the voltage comparison means with high accuracy, and the voltage comparison means can perform a highly accurate and reliable voltage comparison operation.
Further, the correction by the successive comparison does not require a special trimming process such as a non-volatile memory, a laser cut, or a zap, so that the correction work can be simplified.
Furthermore, by configuring the voltage comparison means of this voltage comparison circuit with a CMOS inverter, voltage comparison can be performed at high speed (for example, about several ns), and correction processing can be performed quickly.

According to the present invention, it is possible to highly accurately correct a threshold voltage shift caused by manufacturing variations of the voltage comparison unit, and the voltage comparison unit can perform a highly accurate and reliable voltage comparison operation. It becomes possible.
In addition, since a special trimming process is not required, the correction work can be simplified.

Next, modes for carrying out the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the voltage comparison circuit according to the present invention includes a pair of complementary transistors, an NMOS transistor 11 and a PMOS transistor 12 that perform analog output as a comparator output in accordance with a predetermined threshold. A CMOS inverter 1 that is a comparison means, a reference voltage generation means 5 that generates a reference voltage, an external input signal that is a comparison target signal, and the reference voltage are selectively switched and input to the CMOS inverter 1 as an analog input. Are connected in parallel to the NMOS transistor 11 and are turned on / off by on / off switch 4 (n-1), 4 (n-2). A correction transistor group 3 including correction transistors 3 (n-1), 3 (n-2), and the like. When the reference voltage is connected to the input terminal 1a of the CMOS inverter 1 by the signal selector switch 6, the on / off selector switches of the correction transistors 3 (n-1), 3 (n-2). This is a voltage comparison circuit including a correction switching control circuit 7 that performs control of 4 (n-1), 4 (n-2).
In the present embodiment, the CMOS inverter 1 is used as the voltage comparison means, but is not particularly limited, and can be realized by using, for example, a NAND circuit or a NOR circuit.
Further, although the NMOS transistor connected in parallel to the NMOS transistor 11 of the CMOS inverter 1 is used as the correction transistor, a PMOS transistor connected in parallel to the PMOS transistor 12 of the CMOS inverter 1 can also be used.
Furthermore, a correction transistor may be connected in parallel to each of the transistors 11 and 12 of the CMOS inverter 1.

The correction switching control circuit 7 includes the input signal changeover switch 6, the on / off changeover switches 4 (n−1), 4 (n−2)..., And the output terminal 1 b of the CMOS inverter 1. Connected.
Further, the correction switching control circuit 7 is configured to sequentially compare the reference voltage and the threshold voltage of the CMOS inverter 1 in accordance with an output signal from the CMOS inverter 1, and a comparison result by the successive comparison unit 7a. On / off change-over switches 4 (n-1), 4 (n-2)... Of the correction transistors 3 (n-1) .3 (n-2). A switching correction unit 7b for switching off is provided.

The CMOS inverter 1 outputs an output signal of “1” from the output terminal 1 b of the CMOS inverter 1 when the voltage of the signal input from the input terminal 1 a is smaller than the threshold voltage of the CMOS inverter 1. .
Conversely, when the voltage of the signal input from the input terminal 1 a is equal to or higher than the threshold voltage of the CMOS inverter 1, an output signal “0” is output from the output terminal 1 b of the CMOS inverter 1.

The reference voltage generating means 5 is configured as a circuit that obtains a reference voltage by dividing the power supply voltage V _DD by resistance division using resistors 5a and 5b, for example.
Each of the correction transistors 3 (n−1), 3 (n−2)... Constituting the correction transistor group 3 is configured as an NMOS transistor, and each of the correction transistors 3 (n−1). ) · 3 (n−2)... Are set in common with the drain potential and the source potential of the NMOS transistor 11 in the CMOS inverter 1.

Further, each of the correction transistors 3 (n-1), 3 (n-2)... Has a different transistor size represented by (channel width W / channel length L). The transistor sizes of 3 (n-1), 3 (n-2)... Are weighted to powers of 2.
For example, when the transistor size of the correcting transistor 3 (0) having the largest transistor size is (W ₀ / L ₀ ) (= 2 ⁰ · (W ₀ / L ₀ )), the correcting transistor 3 (0) Next, the transistor size of the correcting transistor 3 (1) having the large transistor size is 2 · (W ₀ / L ₀ ) (= 2 ¹ · (W ₀ / L ₀ )).
Further, the transistor size of the correction transistor 3 (n−1) having the smallest transistor size is 2 ⁿ⁻¹ · (W ₀ / L ₀ ), which is away from the CMOS inverter 1 of the correction transistor 3 (n−1). The transistor size of the correcting transistor 3 (n-2) arranged adjacent to the side is 2 ⁿ⁻² · (W ₀ / L ₀ ).

  Further, the on / off selector switches 4 (n-1), 4 (n-2),... Are connected to the gate electrodes of the correction transistors 3 (n-1), 3 (n-2),. Has a function of switching the gate input of each of the correction transistors 3 (n-1), 3 (n-2)... Between the potential on the input terminal 1a side of the CMOS inverter 1 and the ground potential. Yes.

The voltage comparison circuit configured as described above corrects threshold voltage shifts and errors caused by manufacturing variations of the CMOS inverter 1 and the like, and corrects each of the correction transistors 3 (n−1), 3 (n− 2) is corrected by on / off control.
Here, the threshold voltage V _{th_inv} of the CMOS inverter 1 can be approximated to a value as shown in the following _Equation 1.

Further, K _N and K _P in the equation 1 are represented by the following equations 2 and 3, respectively.

Note that the number 1, number 2, in the equation _3, a _{V DD} power supply _voltage, a threshold voltage of _{V thn} the NMOS transistor _11, the threshold voltage of _{V thp} the PMOS transistor 12, _{(W / L) NMOS} an NMOS transistor 11 (W / L) _PMOS is the transistor size of the PMOS transistor 12, μ _e is the carrier movement speed of the NMOS transistor 11, μ _h is the carrier movement speed of the PMOS transistor 12, and C _ox is the unit area. The capacity per unit is shown.

Most parameters such as V _thn , V _thp , (W / L) _NMOS , (W / L) _PMOS , C _ox , μ _e , and μ _{h in Equation} 1, _Equation 2, and _Equation 3 are CMOS inverters. It is well known that it fluctuates due to the influence of manufacturing variations of 1 and the fluctuation of these parameters causes the fluctuation of the threshold voltage of the CMOS inverter 1.
Accordingly, in the voltage comparator circuit according to the present invention, by the correcting transistor group 3, to correct the value of K _N shown in Equation 2, so as to control the threshold voltage of the CMOS inverter 1 to a proper value .
K _N ′, which is a value after correction of K _N by the correcting transistor group 3, is expressed by the following equation (4).

In Equation 4, X is an integer represented by 0 to ^2n-1 .

  In this example, the correction transistor group 3 is provided on the NMOS transistor 11 side of the CMOS inverter 1, and each of the correction transistors 3 (n-1), 3 (n-2). The correction transistor group 3 is provided on the PMOS transistor 12 side of the CMOS inverter 1 and each of the correction transistors 3 (n−1), 3 (n−2). You can also

Next, a flow when the threshold voltage of the CMOS inverter 1 is corrected by the voltage comparison circuit will be described with reference to FIG.
First, as a premise, when each of the correcting transistors 3 (n-1), 3 (n-2)... Is assumed to have zero manufacturing variation, the value of X in Equation 4 is a full scale value. It is designed so that the threshold voltage of the CMOS inverter 1 at the half value becomes substantially the target threshold voltage.

When a correction start command signal is input to the correction switching control circuit 7 from a correction start command means (not shown), a switch switching signal is output from the correction switching control circuit 7 to the input signal changeover switch 6, The input signal selector switch 6 is switched to the reference voltage side (S01).
At the same time, only the gate electrode of the correction transistor 3 (n-1) on the MSB (Most Significant Bit) side of the correction transistors 3 (n-1), 3 (n-2). The on / off switch 4 (n−1) based on the control from the switching correction unit 7 b of the circuit 7 is connected to the input terminal 1 a side of the CMOS inverter 1. The other correction transistors 3 (n-2)... 3 (0) are connected to the on / off switch 4 (n-2)... 4 (0) based on the control from the switching correction unit 7b. ) To connect to the ground potential (S02).

  In the following, each of the correction transistors 3 (n−1) is controlled by each of the on / off switch 4 (n−1), 4 (n−2). ). 3 (n-2)... Are connected to the input terminal 1a side of the CMOS inverter 1, "each correction transistor 3 (n-1). 3 (n-2). Is turned on by each on / off switch 4 (n-1) 4 (n-2)..., And each correction transistor 3 (n-1) 3 (n-2). That the gate electrodes are connected to the ground potential, “each of the correction transistors 3 (n−1), 3 (n-2)... n-2) ... ".

As described above, it is determined whether the output signal of the CMOS inverter 1 is “1” or “0” with only the correction transistor 3 (n−1) on the MSB side turned on. This is performed by the successive approximation unit 7a of the circuit 7 (S04).
If the output signal is “1” as a result of this determination, it indicates that the threshold voltage of the CMOS inverter 1 is higher than the reference voltage from the reference voltage generating means 5.
Therefore, when the output signal is “1”, the correction transistor 3 (n−2) corresponding to MSB-1 is turned on / off while the correction transistor 3 (n−1) corresponding to the MSB is turned on. The selector switch 4 (n-2) is turned on (S05).

On the other hand, if the output signal is “0” as a result of the determination, it indicates that the threshold voltage of the CMOS inverter 1 is lower than the reference voltage from the reference voltage generating means 5.
Therefore, when the output signal is “0”, the correction transistor 3 (n−1) corresponding to the MSB is turned off and the correction transistor 3 (n−2) corresponding to the MSB-1 is turned on / off. It is turned on by the changeover switch 4 (n-2) (S06).

As described above, in a state where the correction transistor 3 (n-1) on the MSB side and the correction transistor 3 (n-2) corresponding to MSB-1 are turned on / off according to the output signal of the CMOS inverter 1. The on / off state of the correcting transistor 3 (n-1) is determined, and the on / off state of the correcting transistor 3 (n-2) is not yet determined.
Next, in this state, the output signal of the CMOS inverter 1 is again determined by the successive approximation unit 7a, and the correction transistor 3 (n-2) corresponding to MSB-1 and the correction transistor corresponding to MSB-2. 3 (n-3) is turned on / off to determine whether the correction transistor 3 (n-2) is on / off.

Similarly, the ON / OFF states of the correction transistors 3 (n-3), 3 (n-4)... 3 (0) are determined in the same manner.
The ON / OFF of the correction transistors 3 (n-1), 3 (n-2)... Is sequentially determined from the MSB side to the LSB (Least Significant Bit) side. This is continued until ON / OFF of (0) is determined (S03, S07).

That is, in this voltage comparison circuit, the threshold voltage of the CMOS inverter 1 is corrected to the reference voltage using a successive approximation sequence used in an A / D converter or the like.
After the ON / OFF states of all the correction transistors 3 (n-1), 3 (n-2)... Are determined, the input signal changeover switch 6 is controlled by the control from the correction switching control circuit 7. Switching to the external input signal side (S08) completes the correction process.

  As described above, the successive approximation unit 7a of the correction switching control circuit 7 sequentially compares the threshold voltage of the CMOS inverter 1 with the reference voltage according to the output signal of the CMOS inverter 1, and the successive approximation unit 7a Based on the comparison result, the threshold voltage and the reference voltage of the CMOS inverter 1 are obtained by performing correction for switching on / off of each of the on / off switch 4 (n-1), 4 (n-2). Can be made equal to within the range of the potential difference caused by the quantization error.

As a result, it is possible to correct the threshold voltage shift due to manufacturing variations of the CMOS inverter 1 with high accuracy, and the CMOS inverter 1 can perform high-accuracy and highly reliable voltage comparison operation at high speed. It becomes.
Further, the correction by the successive comparison does not require a special trimming process such as a non-volatile memory, a laser cut, or a zap, so that the correction work can be simplified.
Further, since the voltage comparison circuit is composed of the CMOS inverter 1, voltage comparison can be performed at high speed (for example, about several ns), and correction processing can be performed quickly.

It is a circuit diagram which shows the voltage comparison circuit concerning this invention. It is a figure which shows the flow of the voltage comparison method by a voltage comparison circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CMOS inverter 3 Correction transistor group 3 (n-1) ... Correction transistor 4 (n-1) ... On / off switch 5 Reference voltage generating means 6 Input signal switch 7 Correction switching control circuit 7a Successive comparison unit 7b Switching correction unit

Claims (2)

A voltage comparison means comprising at least a pair of complementary transistors for performing an analog input and a comparator output according to a predetermined threshold;
A reference voltage generating means for generating a reference voltage;
An input signal switching means for selectively switching an external input signal which is a comparison target signal and the reference voltage and inputting the analog voltage as an analog input to the voltage comparison means;
A correction transistor group including a plurality of correction transistors connected in parallel with at least one of the complementary transistors and switched on and off by a switching unit;
A voltage comparison circuit comprising correction switching control means for controlling the switching means of each of the correction transistors,
The correction switching control means includes:
When the reference voltage is connected to the input terminal of the voltage comparison means by the input signal switching means,
A successive comparison unit that sequentially compares the reference voltage and a threshold voltage of the voltage comparison unit according to an output signal from the voltage comparison unit;
A switching correction unit that performs on / off switching of the switching means of each of the correction transistors based on the comparison result by the successive approximation unit;
A voltage comparison circuit. A voltage comparison unit including at least a pair of complementary transistors that outputs a comparator according to a predetermined threshold as an analog input, a reference voltage generation unit that generates a reference voltage, an external input signal that is a comparison target signal, An input signal switching means for selectively switching the reference voltage and inputting it to the voltage comparison means as an analog input, and at least one of the complementary transistors is connected in parallel, and the control terminal is turned on / off by the switching means. In a voltage comparison circuit including a correction transistor group including a plurality of correction transistors to be switched, and correction switching control means for controlling the switching means of each correction transistor,
When the reference voltage is connected to the input terminal of the voltage comparison means by the input signal switching means, the correction switching control means,
According to the output signal of the voltage comparison means, the threshold voltage of the voltage comparison means and the reference voltage are sequentially compared,
A threshold voltage correction method for a voltage comparison circuit, wherein the threshold voltage of the voltage comparison means is corrected by switching on / off each switching means of the correction transistor group based on the result of the successive comparison. .

Images