JPH0595262A - Analog input circuit - Google Patents

Abstract

PURPOSE:To provide the analog input circuit applied to a CMOSIC which is operated when a voltage of an input signal is within a full power supply voltage range. CONSTITUTION:An input signal IN is inputted to a noninverting input terminal of a P type comparator 3 and an N type comparator 4, and a reference voltage Ref is given to each inverting input terminal. Moreover, analog switches 5,6 are interposed between output terminals of the comparators 3,4. The analog switch 5 consists of a P-channel transistor(TR) and the analog switch 6 consists of an N-channel TR. An input signal and a reference voltage are given in common to the comparators.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a CMOS IC (Compleme
ntary Metal Oxide Semiconductor Integrated Circui
The invention relates to an analog input circuit of t), and particularly to an analog input circuit in which the voltage of an input signal operates in the entire power supply voltage range.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional analog input circuit in a CMOS IC.

Conventionally, in a CMOS IC, a single comparator is used as an analog input circuit. That is, the input signal IN is applied to the non-inverting input terminal of the comparator 10.
Is input, and the reference voltage _Ref is applied to the inverting input terminal. Also, this comparator 10 has
Power supply voltages V _SS and V _CC are provided.

In this case, the voltage V _IN of the input signal IN required for the comparator 10 to operate is in the range shown in the following formula 1 or 2 depending on whether the comparator 10 is P type or N type. However, V _TP is a threshold voltage when the comparator 10 is a P type, and V _TN is a threshold voltage when the comparator 10 is an N type.

[0005]

[Equation 1] V _SS <V _IN <V _CC −V _TP

[0006]

[Formula 2] V _SS + V _TN <V _IN <V _CC

[0007]

However, in the analog input circuit of the conventional CMOS IC, when the voltage V _{IN of the} input signal is V _CC -V _TP or more (in the case of the P-type comparator), or the input voltage is V. If it is _SS + V _TN or less (in the case of N type comparator), there is a drawback that an output corresponding to the input signal cannot be obtained.
That is, the analog input circuit in which the voltage V _{IN of the} input signal can operate in the entire power supply voltage range (V _{SS to} V _CC ) is usually constructed by using the depletion type transistor. Therefore, a special process is required to form a depletion type transistor, and a CMOS IC usually composed of enhancement type transistors is required.
Difficult to apply to.

Therefore, even in the CMOS IC, there is a demand for an analog input circuit capable of operating the input signal voltage in the entire power supply voltage range.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an analog input circuit that can operate in the entire power supply voltage range of an input signal and can be applied to a CMOS IC. And

[0010]

An analog input circuit according to the present invention includes a P-type comparator having an input signal applied to one input terminal and a reference voltage applied to the other input terminal.
An N type comparator having one input terminal supplied with the input signal and the other input terminal supplied with the reference voltage, and a first switch interposed between an output terminal and an output terminal of the P type comparator. , And a second switch interposed between the output end of the N-type comparator and the output terminal.

[0011]

In the present invention, a P-type comparator and an N-type comparator are provided, and the input signal and the reference voltage are commonly given to both comparators. Therefore, when the power supply voltages are V _SS and V _CC , the threshold of the N-type comparator is V _TN , and the threshold of the P-type comparator is V _TP , the voltage of the input signal is V _SS + V _TN or less. In this case, the N type comparator does not operate, but the P type comparator operates normally. on the other hand,
When the voltage of the input signal is V _CC -V _TP or more, the P type comparator does not operate, but the N type comparator operates normally. Therefore, by appropriately switching the outputs of the P-type comparator and the N-type comparator by the first and second switches, an analog input circuit in which the voltage of the input signal operates in the entire power supply voltage range (V _{SS to} V _CC ) is obtained. be able to. A P-channel transistor and an N-channel transistor can be used as the first and second switches, and a predetermined operation can be obtained by applying the input signal to the gates of these transistors, for example.

[0012]

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

FIG. 1 is a circuit diagram showing an analog input circuit according to the first embodiment of the present invention.

This analog input circuit is composed of an input section 1 and a select circuit section 2. The input section 1 is composed of a P-type comparator 3 and an N-type comparator 4, and an input signal IN is commonly applied to the non-inverting input terminals of these comparators 3 and 4. A reference voltage _Ref is commonly applied to the inverting input terminals of these comparators 3 and 4. These comparators 3, 4
Compares the voltage of the input signal IN with the reference voltage _Ref and outputs the result.

On the other hand, the select circuit section 2 is composed of an analog switch 5 composed of a P-channel transistor and an analog switch 6 composed of an N-channel transistor. The switch 5 is interposed between the comparator 3 and the output terminal, and the gate thereof receives the input signal IN. The switch 6 is interposed between the comparator 4 and the output terminal, and its gate is supplied with the input signal IN. The outputs of the comparators 3 and 4 are selected by the switches 5 and 6 and output to the output terminal as the output signal OUT.

Next, the operation of the circuit of this embodiment will be described. However, in order to facilitate the explanation, depending on the voltage V _IN of the input signal IN, as shown in FIG.
Description will be given separately for C.

In region A, the input signal voltage V _IN is V _SS ≤V _IN
<V _TN (provided that V _SS is 0 V). In this region, the N-type comparator 4 does not operate and the output is indefinite, but the P-type comparator 3 operates normally. Further, since the switch 6 is turned off and the switch 5 is turned on, the output signal OUT is
The output of the comparator 3 is sent out.

In the region B, the input signal voltage V _IN is V _TN ≤V _IN
This is the case where ≦ V _CC −V _TP . In this region, both comparators 3 and 4 operate normally. Also, the switches 5 and 6 are both turned on. Therefore, the output signal OUT becomes the average of the outputs of the comparators 3 and 4, and the effect of offsetting the offsets of the comparators 3 and 4 is obtained.

In region C, the input signal voltage V _IN is V _CC -V _TP
This is the case where <V _IN ≦ V _CC . In this region, the P type comparator 3 does not operate, but the N type comparator 4 operates normally. Further, the switch 5 is turned off and the switch 6 is turned on. As a result, the output of the comparator 4 is sent as the output signal OUT.

In this embodiment, as described above, the N type comparator 4 operates in the input voltage range in which the P type comparator 3 does not operate, and the P type comparator 3 operates in the input voltage range in which the N type comparator 4 does not operate. In order to operate, the voltage of the input signal can operate in the entire input voltage range (0 to V _CC ).

FIG. 3 is a circuit diagram showing an analog input circuit according to the second embodiment of the present invention.

The analog input circuit according to this embodiment also has the first
The input unit 11 and the select circuit unit 12 are similar to the embodiment of
It is composed by.

The input section 11 is composed of a P-type comparator 13 and an N-type comparator 14. The input signal IN is commonly applied to the non-inverting input terminals of these comparators 13 and 14, and the inverting input terminals thereof are supplied. _Are commonly provided with a reference voltage _Ref .

The select circuit 12 includes an analog switch 15 including a P-channel transistor interposed between the comparator 13 and the output terminal, and an analog switch including an N-type transistor interposed between the comparator 14 and the output terminal. It is composed of a switch 16, and the gates of these transistors are all connected to the output terminal.

In this embodiment, the same effect as in the first embodiment can be obtained, and in addition, the surge voltage from the input terminal can be prevented from being applied to the gates of the analog switches 15 and 16. There is an effect.

[0026]

As described above, the analog input circuit according to the present invention includes the P-type comparator and the N-type comparator, and the input signal and the reference voltage are commonly applied to these comparators. Can operate in the entire power supply voltage range.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an analog input circuit according to a first embodiment of the present invention.

FIG. 2 is a graph showing the operation of the analog input circuit according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing an analog input circuit according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 11; Input section 2, 12; Select circuit section 3, 4, 13, 14; Comparator 5, 6, 15, 16; Analog switch

[Procedure amendment]

[Submission date] September 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Added

[Correction content]

FIG. 4 is a circuit diagram showing a conventional analog input circuit.

Claims (2)

[Claims] 1. A P-type comparator having an input signal applied to one input terminal and a reference voltage applied to the other input terminal, and an input signal applied to one input terminal and the reference voltage applied to the other input terminal. A given N type comparator, a first switch interposed between the output terminal and the output terminal of the P type comparator, and a first switch interposed between the output terminal of the N type comparator and the output terminal Second
And an analog input circuit. 2. The analog input circuit according to claim 1, wherein the first switch is a P-channel transistor, and the second switch is an N-channel transistor.