JPH01128614A - Voltage comparing circuit - Google Patents

Abstract

PURPOSE:To reduce energy consumption due to a pull-up resistance by using an open drain (or an open collector) type comparator and an analog switch, which has the control terminal to be active low, respectively in two numbers and obtaining 'H' level and 'L' level outputs with the switching operation of the both. CONSTITUTION:When the electric potential of a non-inverting input terminal 6 is obtained as a V1, the electric potential of a non-inverting input terminal 7 is obtained as a V2 and the electric potential of an output terminal 9 is obtained as a V0, in case of V1<V2, a condition is stabilized so that the output step transistor of a comparator 5 can be turned on, the output step transistor of a comparator 4 can be turned off, an analog switch 2 can be turned on and an analog switch 3 can be turned off. In case of V1>V2, the condition is stabilized so that the output step transistor of the comparator 5 can be turned off, the output step transistor of the comparator 4 can be turned on, the analog switch 2 can be turned off and the analog switch 3 can be turned on. Even in any stable condition, when a load condition to the output terminal 9 is a high impedance, a current is not flown to a resistance 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a voltage comparator circuit used in a pulse receiving circuit in digital communication, and particularly to a voltage comparator circuit that uses an open-train (or open collector) type comparator. The present invention relates to a voltage comparator circuit.

[Conventional technology]

Conventionally, this type of voltage comparison circuit has been comprised of an open drain (open collector) type comparator 21 and a sol-up resistor 22, as shown in FIG. According to this voltage comparison circuit, the non-inverting input terminal 23
The potential of VICV:I.

The potential of the inverting input terminal 24 is set to Vz[:V], and the potential of the output terminal 28 is set to Vz[:V].
The potential of is Vo (V), and the resistance value of the pull-up resistor 22 is R
o (Ω), and the potential of the power supply terminal 27 is VDDcv].

7 bundles <V 2 When.

V(1=O[:V] Tona Shear Sol Up Resistance 22 A current flows.

amount of power is consumed by the pull-up resistor 22.

[Problem that the invention seeks to solve]

In the conventional voltage comparator circuit as described above, one method of reducing power consumption in the pull-up resistor 22 is to increase the resistance value R of the pull-up resistor 22.

However, this is because stray capacitance C8 generally exists between the output terminal 28 and the negative power supply input terminal 26.

When changing from the state of Vl <v to the state of Vl >V2, as shown in FIG. 4, when the resistance value Ro of the resistor 22 is small, as shown in (a), when the output terminal 28 is
As shown in b), a "slug" occurs at the rising edge of the output waveform of the output terminal 28, and this "slug" can be overcome by increasing the resistance value R of the pull-up resistor 22. It will make it worse. Therefore, especially when high-speed operation is required in such a voltage comparator circuit, the resistance value R of the pull-up resistor 22 cannot be made too large, and the power consumption PG due to the pull-up resistor 22 increases. The present invention is an attempt to solve these problems of conventional products, while maintaining high-speed operation.

The present invention provides a voltage comparison circuit that reduces power consumption due to pull-up resistors.

[Failure to solve the problem]

The voltage comparison circuit of the present invention includes a resistor having one end connected to a power source, a first analog switch and a second analog switch having an analog signal input terminal connected to the other end of the resistor, and an output terminal of the first analog switch. a first open drain (or open collector) type comparator connected to an analog signal output terminal of the first analog switch and an active low (m L, ow ) control terminal of the second analog switch; The analog signal output terminal of the second analog switch and the first analog switch
A non-inverting input terminal is connected to an active - (2 LOW) control terminal of the first comparator, and a second inverting input terminal is connected to an inverting input terminal of the first comparator. It is configured with a second open drain (or open collector) type comparator connected to the non-inverting input terminal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

This voltage comparison circuit includes a resistor 1 whose one end is connected to a power supply, a first analog switch 2 and a second analog switch 3 whose other end is connected to an analog signal input terminal CI), and an output terminal. are the analog signal output terminal (0) of the first analog switch 2 and the control terminal (C
), and the output terminal is the analog signal output terminal (0) of the second analog switch 3 and the active state of the first analog switch 2. -(= edict,
I. 7. . Oh, seasonal. , Yayo.

and a second open drain (or open collector type comparator 5.

Next, the operation of this voltage comparison circuit will be explained.

In FIG. 1, the potential of the non-inverting input terminal 6 is vl + the potential of the inverting input terminal 7 is v2, and the potential of the output terminal 8 is Vo
shall be.

First, considering the states of vl and v2, the output stage transistor of comparator 5 is ON, the output stage transistor of comparator 4 is OFF, analog switch 2 is ON, and analog switch 3 is OFF.

stabilizes in the state of In this case, if we simply replace the output stage transistors of converters 4 and 5 with switches 4/ and 5/ and the analog switches 2 and 3 with switches 2/ and 3/, we can draw an equivalent circuit as shown in Figure 2. (,) becomes.

Further, considering the state of Vl>Vz in FIG. 1, the output stage transistor of the comparator 5 is OFF, the output stage transistor of the comparator 4 is ON, the analog switch 2 is OFF, and the analog switch 3 is stable in the ON state. At this time, if we simply replace the output stage transistors of the converters 4 and 5 with switches 4/ and 5/ and the analog switches 2 and 3 with switches 2/ and 3/, we can draw an equivalent circuit as shown in Figure 2 (b). ).

As is clear from FIGS. 2(a) and (b), r Vt
When <v2, vo=″L” (=O[:V]), t and v
When L>v2, Vo=″′H”(=Vl)D)
l! :Even in stable state, output terminal 8
If the load condition for ° is high impedance, resistor 1
No current flows through. Also, analog switches 2 and 3 are C
-The MO8 configuration has extremely low static power consumption.

In addition, in Fig. 1, resistor 1 has +VO from "H" to @
Simultaneous O of analog switch 2 and comparator 4 at the moment of each change from L'' to H# and from L# to H#.
This effectively acts to limit the current between VDD and Ov due to N, or when analog switch 3 and comparator 5 are turned on simultaneously.

〔Effect of the invention〕

As is clear from the above description, 1. the present invention uses two analog switches each having an open drain (or open collector) type comparator and an active low control terminal, and 2. the switching operation of both.
By obtaining H' level a L w level output,
This has the effect of reducing power consumption by the pull-arno resistor while maintaining high-speed operation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the voltage comparison circuit of the present invention, FIG. 2 is an explanatory diagram showing an outline of the operation of the voltage comparison circuit of FIG. 1, and FIG. 3 is an example of a conventional voltage comparison circuit. Circuit diagram shown,
FIG. 4 is an explanatory diagram showing operating waveforms of the voltage comparison circuit of FIG. 3. In the figure, 1 is a resistor, 2 and 3 are analog switches yf, and 4
, 5 is a comparator, 6 is a non-inverting input terminal, 7 is an inverting input terminal, 8 is an output terminal. 2/, 3/ indicate the switching operation of analog switches 2 and 3, t, 4/
, 5/ are switches indicating the switching operation of the open drain (or open collector) transistors of the comparators 4 and 5. Figure 1 Figure 2 L

Claims (1)

[Claims] 1. A resistor having one end connected to a power supply, a first analog switch and a second analog switch having an analog signal input terminal connected to the other end of the resistor, and an output terminal having an analog signal of the first analog switch. a first open drain (or open collector) type comparator connected to a signal output terminal and an active low control terminal of the second analog switch;
is connected to an analog signal output terminal of an analog switch and an active low control terminal of the first analog switch, and a non-inverting input terminal is connected to an inverting input terminal of the first comparator, and an inverting input terminal is a second open drain (or open collector) connected to the non-inverting input terminal of the first comparator.
A voltage comparison circuit comprising a type comparator.