Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Negative resistance type
Reexamination Certificate
1998-10-26
2001-05-01
Kim, Jung Ho (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Negative resistance type
Reexamination Certificate
active
06225860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a source voltage detecting circuit suitable for integrated circuits which is used to monitor the source voltage fed to a microcomputer or the like and to prevent a runaway or malfunction of a microcomputer or the like due to a lowering in said source voltage.
2. Description of Prior Art
An example of a source voltage monitoring circuit which has heretofore been used in common is shown in FIG.
10
. In the source voltage monitoring circuit shown in
FIG. 10
, a reference voltage provided by a Zener diode Z
1
, is fed to one of the inputs of a comparator COM
1
, and the source voltage V
CC
is divided by resistors R
10
and R
11
, one such divisional voltage being fed as the detected voltage to the other input of said comparator COM
1
. The source voltage drop is constantly monitored in that the reference voltage and the detected voltage is compared with each other by the comparator. In the source voltage monitoring circuit shown in
FIG. 10
, however, the reference voltage section, the detection voltage section and the comparator section each consume electric current, making it difficult to achieve lower consumption, so that this circuit is not suitable for use in battery-driven portable devices.
Accordingly, a circuit example as shown in
FIG. 11
has been put into practical use to keep pace with the recent trend toward lower current consumption. The circuit example shown in
FIG. 11
comprises a source voltage drop detecting circuit
11
using transistors Q
2
-Q
3
and resistors R
13
-R
18
, a differential amplifier type comparator
12
using transistors Q
4
-Q
8
and resistors R
19
-R
24
, and an output control circuit
13
using transistors Q
10
-Q
12
and resistors R
21
-R
24
, said source voltage drop detecting circuit
11
being compensated for temperature by V
BE
multiplier
14
using a transistor Q
2
and resistors R
13
-R
14
. And for hysteresis formation, the difference in V
BE
between the transistors Q
6
and Q
7
is utilized, said transistor Q
7
having an emitter area which is N times as large as the transistor Q
6
. Further, capacitors C
1
and C
2
are provided for improving the response characteristic.
SUMMARY OF THE INVENTION
In the conventional circuit as described above, although the reference voltage section and the detection voltage section V
CC
are disposed on the same line between V
CC
, as compared with
FIG. 10
, there are still two lines with current constantly flowing therethrough: a line extending from the multiplier to a transistor Q
3
for reference voltage, and consumption by a constant voltage source Q
8
for differential amplification. Therefore, a large resistance has to be used for lower consumption, resulting in a larger chip area, a fact which has been a major cause of increased costs.
In the reference voltage source, the voltage detecting circuit, and the voltage detecting circuit using a differential amplifier type comparator as generally shown in
FIGS. 10 and 11
, about 30 elements including transistors, resistors and capacitors are required to improve output current, temperature characteristic, hysteresis, response characteristic, etc., for a circuit, so that it has been difficult to further reduce costs for an integrated circuit.
Further, the detection voltage is determined by a circuit constant, and a circuit design has to be made for each required detection voltage; in an integrated circuit, a pattern mask has to be prepared each time.
Accordingly, this invention tackles these problems and is intended to provide a source voltage detecting circuit suitable for integrated circuits, using very simple circuit arrangement to satisfy the various characteristics required for source voltage detection, and to make it possible to control the detection voltage in the wafer process.
To achieve the above object, specifically, this invention provides a source voltage detecting circuit, comprising first and second resistors and a reference voltage source which are connected in series between a power source and the ground, wherein the point of connection between said first and second resistors is connected to the output terminal of a negative resistance characteristic section, and the point of connection between said second resistor and the reference voltage source is connected to the input terminal of the negative resistance characteristic section.
Further, this invention also provides a source voltage detecting circuit in the form of a base modulation bipolar transistor wherein said negative resistance characteristic section includes a first electrically conductive type collector region serving as an output section, a second electrically conductive type base region formed through a first PN junction with respect to said collector region, and a first electrically conductive type emitter region formed through a second PN junction with respect to said base region, and wherein
said base region includes a first base region disposed adjacent said emitter region through said second PN junction, a base contact region spaced from said first base region and serving as the input section of the negative resistance characteristic section and serving to take out the base electrode, and a second base region of low impurity concentration formed between said first base region and said base contact region, said second base region provided therein with a gate region having a first electrically conductive type connected to the collector region, the arrangement being such that
when a forward bias is applied between said base contact region and said emitter region and when the collector region is energized with a reverse bias with respect to said base collector region, the base current flowing through said second base region is modulated to provide a negative resistance characteristic.
Further, this invention also provides source voltage detecting circuit wherein the negative resistance characteristic section uses the source of a junction type FET as the input section of the negative resistance characteristic section, the drain of the junction type FET being connected to the base of a bipolar transistor, the gate of said junction type FET being connected to the collector of said bipolar transistor, the collector of said bipolar transistor being the output section of the negative resistance characteristic section.
In the source voltage detecting circuit of this invention constructed in the manner described above, when source voltage decreases until the voltage across the second resistor is not more than the pinch-off voltage for the negative resistance characteristic section, said negative resistance characteristic section is switched on to produce an output. In this negative resistance characteristic section, no current whatever is consumed during standing by. Therefore, the current consumption occurs in the first and second resistors in the line extending to the reference voltage source, so that super low current consumption is made possible. The temperature characteristic for detection voltage can be cancelled by the pinch-off voltage at the negative resistance characteristic section, the reference voltage source, the first and second resistors, without requiring any special circuit element. As for the hysteresis, it is determined by the ratio of the first resistor to the resistor connected to the grounded side of the negative resistance characteristic section, and the number of elements is reduced to about ⅓ of that in the prior art, and the chip size in an integrated circuit can be greatly reduced. Further, since the detection voltage is determined by the pinch-off voltage, it can be controlled as required in the process.
REFERENCES:
patent: 3670183 (1972-06-01), Ager et al.
patent: 4028562 (1977-06-01), Zuleeg
patent: 5281871 (1994-01-01), Mori et al.
patent: 5304858 (1994-04-01), Heitzer et al.
patent: 6-44210 (1994-06-01), None
patent: 7-336200 (1995-12-01), None
Shimizu Katsuya
Shimogasa Toshihiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Kim Jung Ho
Kondenshi Corporation
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