JP2005165792A - Low-input-voltage malfunction prevention circuit with overvoltage protection function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-input-voltage malfunction prevention circuit with an overvoltage protection function, enabling reduction of the number of semiconductor integrated circuit and a chip area. <P>SOLUTION: A first current source CF, having dependency to an input voltage 1, is connected to one end of a current mirror circuit CM having second and third transistors 4, 5 of reverse polarity. The other end of the current mirror circuit CM is connected to one end of a resistor 6. The other end of the resistor 6 is connected to the source of a fourth transistor 7 of reverse polarity, of which drain is connected to the input voltage 1. A second constant current source 8 is connected between the gate of the fourth transistor 7 of reverse polarity and the input voltage 1, while a zener diode 9 is connected between the gate of the fourth transistor 7 and the ground. A drain voltage VA of the third transistor 5 of reverse polarity, and a voltage VB corresponding to a low input voltage detection threshold and an overvoltage detection threshold are supplied to the comparator 11, as input voltages thereto. A signal VCOUT detecting low input voltage and overvoltage is obtained, as an output of the comparator 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a circuit for preventing malfunction and protecting peripheral components when a input voltage is low or high in a semiconductor integrated circuit.

Hereinafter, as the above circuit, FIG. 5 shows a conventional low input voltage detection circuit and overvoltage detection circuit for an input voltage, which will be described.
In FIG. 4, 1 is an input voltage, 14 is a control signal generation circuit based on this input voltage 1, 29 is a low input voltage detection circuit for input voltage 1, 30 is an overvoltage detection circuit for input voltage 1, and the control signal generation circuit 14 is connected to a current source 12 for supplying a current via a switch 13.

  In the low input voltage detection circuit 29, the voltage Va obtained by dividing the input voltage 1 by the resistors 21 and 22 and the voltage VL of the constant voltage 23 are compared by the comparator 24, and as shown in FIG. When the input voltage detection threshold is lower than and higher than the input voltage detection threshold VL, low and high level signals are output as the output signal c, respectively.

  Further, in the overvoltage detection circuit 30, the voltage d obtained by dividing the input voltage 1 by the resistors 25 and 26 and the voltage VH of the constant voltage 27 are compared by the comparator 28, and as shown in FIG. High and low level signals are output as the output signal f when it is lower and higher than the threshold value VH, respectively.

  The output signal c of the low input voltage detection circuit 29 and the output signal f of the overvoltage detection circuit 30 are input to the AND circuit 31 as shown in FIG. 5, and the detection signal VCOUT is output as shown in FIG. Yes. Then, the switch 13 is turned off by this detection signal VCOUT to cut off the current I2 of the current source 12 to control the operation of the control signal generation circuit 14, and the detection signal VCOUT is input to the AND circuit 15 to control the control signal generation circuit 14. The output signal is turned on / off, and on / off control is performed to prevent malfunction and protect peripheral components. VOUT is an output signal of the AND circuit 15.

  Thus, conventionally, in order to realize low input voltage malfunction prevention and overvoltage protection, it is necessary to separately configure the low input voltage detection circuit 29 and the overvoltage detection circuit 30 as shown in FIG.

  However, in the conventional configuration, since the low input voltage detection circuit 29 and the overvoltage detection circuit 30 are separately configured, there is a problem that the number of constituent elements increases and the chip area increases.

  The present invention solves the above-described conventional problems, and realizes a low input voltage detection circuit and an overvoltage detection circuit in the same circuit to enhance additional functions, reduce the number of semiconductor integrated circuit elements, and reduce the chip area. It is an object of the present invention to provide a low input voltage malfunction prevention circuit with an overvoltage protection function.

  In order to achieve the above-mentioned object, the invention according to claim 1 of the present invention is a first current which is constituted by a first transistor having a single polarity and has a dependency on the input voltage. Connected to one end of a current mirror circuit composed of second and third transistors of opposite polarity to the first current source, and connected to one end of a resistor to the other end of the current mirror circuit, The other end of the resistor is connected to the source of a fourth transistor of reverse polarity with a drain connected to the input voltage, and a second current source is connected between the gate of the fourth transistor of reverse polarity and the input voltage. A zener diode is connected between the second current source and ground, the other end of the current mirror circuit is connected to a comparator as one input side voltage, and the other input side power of the comparator is connected. As one in which gives a constant voltage corresponding to a low input voltage detection threshold and overvoltage detection threshold, and wherein the use of the output of the comparator as the detection signal. According to this configuration, the low input voltage detection circuit and the overvoltage detection circuit can be realized by the same circuit, the low input voltage malfunction prevention and the overvoltage protection are achieved by reducing the number of semiconductor integrated circuit elements and reducing the chip area. realizable.

  The invention according to claim 2 is the invention according to claim 1, wherein the first current source is connected to the source with the input voltage, and a predetermined voltage is applied between the gate and the source. The first transistor has a polarity, and the variation in the input voltage is captured as the variation in the output current of the first transistor.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the operation control of the control signal generation circuit is performed using the detection signal of the comparator output. Is.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the output signal of the control signal generation circuit is controlled using the detection signal of the comparator output. It is characterized by performing.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein a MOS transistor or a bipolar transistor having the same polarity is provided in each of the first to fourth transistors. It is characterized by being used.

  The present invention has an overvoltage protection circuit function by controlling the input side voltage of the comparator of the low input voltage malfunction prevention circuit using the current source having the above-described configuration and dependency on the input voltage. In addition, a low input voltage malfunction prevention circuit with an overvoltage protection circuit function can be configured, the number of semiconductor integrated circuit elements can be reduced, and the chip area can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the structure same as the structure shown in the conventional FIG. 5, and description is abbreviate | omitted.
[Embodiment 1]
FIG. 1 is a circuit diagram of a low input voltage malfunction prevention circuit with an overvoltage protection function according to Embodiment 1 of the present invention.

  In FIG. 1, CF is a first current source having a dependency on an input voltage 1, and the first current source CF has a source connected to the input voltage 1 and a predetermined voltage 2 applied between the gate and the source. The unipolar first transistor 3 is formed of a Pch C-MOS transistor. One end of the current mirror circuit CM is connected to the drain of the unipolar first transistor 3 which is the output end of the first current source CF.

  The current mirror circuit CM is composed of second and third transistors 4 and 5 having opposite polarities made of Nch C-MOS transistors, and is connected to the output terminal of the first current source 3 as one end of the current mirror circuit CM. The drain and gate of the transistor 4 and the gate of the third transistor 5 are connected, and the sources of the second and third transistors 4 and 5 are connected to the ground. One end of the resistor 6 is connected to the other end of the current mirror circuit CM, that is, the drain of the third transistor 5.

  The other end of the resistor 6 is connected to the source of a fourth transistor 7 of reverse polarity composed of an Nch C-MOS transistor whose drain is connected to the input voltage 1, and the gate of the fourth transistor 7 of reverse polarity is connected to the source. A second current source 8 is connected between the input voltage 1 and a zener diode 9 is connected between the second current source 8 and ground.

  Further, the drain of the third transistor 5 which is the other end of the current mirror circuit CM is connected to one input of the comparator 11 as one input side voltage, and the constant voltage 10 of the other input side voltage of the comparator 11 is connected. A voltage VB is applied. The voltage VB of the constant voltage 10 corresponds to the low input voltage detection threshold VL and the overvoltage detection threshold VH.

As an output of the comparator 11, a low input voltage and overvoltage detection signal VCOUT is obtained.
The detection signal VCOUT is used as a drive signal for the switch 13 and an input signal for the AND circuit 15 as in the prior art.

The operation of the low input voltage malfunction prevention circuit with an overvoltage protection function configured as described above will be described based on the operation explanatory diagrams of FIGS. 3 and 4 together with FIG.
A voltage 2 is applied between the gate and the source of the first current source CF constituted by the unipolar transistor 3, and the first current source CF has an input voltage 1 (voltage value is V1). If the voltage fluctuates, the voltage between the gate and drain of the unipolar transistor 3 fluctuates. Therefore, the channel modulation effect has a dependency on the input voltage 1, that is, when the voltage value V1 of the input voltage 1 increases, the output current I3 increases. It becomes a current source. The current I3 also flows through the fourth transistor 7 having the reverse polarity by the current mirror circuit CM including the second and third transistors 4 and 5 having the reverse polarity.

Here, if the gate voltage of the fourth transistor 7 of reverse polarity is V (M7 / G) and the forward voltage of the Zener diode 9 is VZD,
When V1 <VZD V (M7 / G) = V1 (1)
When V1 ≧ VZD V (M7 / G) = VZD (2)
It becomes. However, here, when V1 <VZD, the second current source 8 is an ideal current source that does not cause a voltage drop at both ends. Here, assuming that the gate-source voltage of the fourth transistor 7 of reverse polarity is VGS and the resistance value of the resistor 6 is R6, the voltage of the drain of the third transistor 5 from the equations (1) and (2), that is, The voltage VA at one input of the comparator 11 is
When V1 <VZD VA = V1-VGS-I3 · R6 (3)
When V1 ≥ VZD VA = VZD-VGS-I3 · R6 (4)
It becomes. Therefore, from the equation (3), when the voltage is low (V1 <VZD), as shown in FIG. 3, VA rises as V1 rises. Thereby, when V1 is lower than the low input voltage malfunction circuit threshold VL (FIG. 3), the detection signal VCOUT outputs a low level and a high level, respectively, when it is high. Further, from the equation (4), at the time of overvoltage (V1 ≧ VZD), as shown in FIG. 3, I3 increases as V1 increases, so VA decreases as V1 increases. Thus, when V1 is lower than the overvoltage protection circuit threshold value VH (FIG. 3), the detection signal VCOUT outputs a high level and a low level when it is high. Therefore, the relationship between the voltages VA and VB input to the comparator 11 and the input voltage V1, and the output of the comparator 11, that is, the relationship between VCOUT and V1, is as shown in FIG. As shown in FIG. 3, the voltage VB corresponds to the low input voltage detection threshold VL and the overvoltage detection threshold VH as described above, and the low input voltage and overvoltage detection signal VCOUT is obtained as the output of the comparator 11.

  Then, by using this detection signal VCOUT, the control signal generation circuit 14 is turned on / off by turning on / off the switch 13 for supplying the current I2 to the control signal generation circuit 14, that is, the control signal generation circuit 14 Operation control is performed, and the detection signal VCOUT is input to the AND circuit 15 together with the output signal of the control signal generation circuit 14 to turn on / off the output signal and control the output signal of the control signal generation circuit 14. .

As described above, according to the first embodiment, by using the first current source CF having dependency on the input voltage 1 to control the input side voltage of the comparator 11, the overvoltage protection circuit function is also achieved. In addition, a low input voltage malfunction prevention circuit with an overvoltage protection circuit function can be configured. By realizing the low input voltage detection circuit and the overvoltage detection circuit in the same circuit in this way, the number of semiconductor integrated circuit elements can be reduced. It is possible to reduce the chip area.
[Embodiment 2]
Even if a part or all of the MOS transistors in the circuit described in the first embodiment are replaced with bipolar transistors having the same polarity, the same functions and effects can be obtained. In the second embodiment, as shown as an example in FIG. 2, all MOS transistors are replaced with bipolar transistors having the same polarity.

  In FIG. 2, a unipolar first transistor 17 composed of a P-type bipolar transistor is provided in place of the unipolar first transistor 3 composed of a Pch C-MOS transistor. In place of the second and third transistors 4 and 5 having opposite polarities, second and third transistors 18 and 19 having opposite polarities made of N-type bipolar transistors are provided, and further comprising N-channel C-MOS transistors. Instead of the fourth transistor 7 having the reverse polarity, a fourth transistor 20 having the reverse polarity made of an N-type bipolar transistor is provided.

  Further, the first current source CF constituted by the unipolar transistor 16 is supplied with a voltage 16 between the base and the emitter of the unipolar transistor 16. The effect is dependent on the input voltage 1, that is, a current source in which the output current increases as the input voltage 1 increases. Thereafter, the same operation as described in the first embodiment operates as a low input voltage malfunction prevention circuit with an overvoltage protection circuit function.

  The low input voltage malfunction prevention circuit with an overvoltage protection circuit function according to the present invention reduces the number of semiconductor integrated circuit elements and the chip area by realizing the low input voltage detection circuit and the overvoltage detection circuit in the same circuit. In a semiconductor integrated circuit, the semiconductor integrated circuit is useful as a technique related to malfunction and protection of peripheral components when the power supply voltage is low and high.

1 is a circuit diagram of a low input voltage malfunction prevention circuit with an overvoltage protection function according to a first embodiment of the present invention. FIG. It is a circuit diagram of the low input voltage malfunction prevention circuit with an overvoltage protection function by Embodiment 2 of this invention. It is operation | movement explanatory drawing of the overvoltage and undervoltage detection in the low input voltage malfunction prevention circuit with an overvoltage protection function of this invention. It is output control operation explanatory drawing using the detection signal in the low input voltage malfunction prevention circuit with an overvoltage protection function of this invention. It is a circuit diagram of the low input voltage malfunction prevention and overvoltage protection circuit regarding the input voltage which comprised the conventional low input voltage detection circuit and the overvoltage detection circuit separately. It is operation | movement explanatory drawing of the low input voltage malfunction prevention regarding an input voltage, and the overvoltage protection which comprised the conventional low voltage malfunction prevention circuit and the overvoltage protection circuit separately.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input voltage 2,16 Predetermined voltage 3,17 Unipolar 1st transistor 4,5,18,19 Reverse polarity 2nd, 3rd transistor 6 Resistance 7,20 Reverse polarity 4th transistor 8 2nd Current source 9 Zener diode 10 Constant voltage 11 Comparator 12 Current source of control signal generation circuit 13 Switch for controlling operation of control signal generation circuit 14 Control signal generation circuit 15 AND circuit CF First current source CM Current mirror circuit VA, VB Comparator input side input voltage VZD Zener diode forward voltage VL Low input voltage detection threshold VH Overvoltage detection threshold VCOUT detection signal VOUT output signal

Claims (5)

A first current source configured by a unipolar first transistor having dependency on the input voltage is connected to the input voltage;
One end of a current mirror circuit composed of second and third transistors of opposite polarity is connected to the first current source,
One end of a resistor is connected to the other end of the current mirror circuit,
The other end of the resistor is connected to the source of a fourth transistor of reverse polarity with the drain connected to the input voltage,
A second current source is connected between the gate of the fourth transistor of reverse polarity and the input voltage;
A zener diode is connected between the second current source and ground;
The other end of the current mirror circuit is connected to the comparator as one input side voltage,
A low input voltage malfunction with an overvoltage protection function, wherein a constant voltage corresponding to a low input voltage detection threshold and an overvoltage detection threshold is given as the other input side voltage of the comparator, and the output of the comparator is used as a detection signal Prevention circuit. The first current source is constituted by a first transistor having one polarity, the input voltage of which is connected to the source and a predetermined voltage is applied between the gate and the source, and the fluctuation of the input voltage is detected by the first transistor. The low input voltage malfunction prevention circuit with an overvoltage protection function according to claim 1, wherein the low input voltage malfunction prevention circuit according to claim 1 is captured. 3. The low input voltage malfunction prevention circuit with an overvoltage protection function according to claim 1, wherein operation control of the control signal generation circuit is performed using the detection signal of the comparator output. The low input voltage malfunction with an overvoltage protection function according to any one of claims 1 to 3, wherein the output signal of the control signal generation circuit is controlled using the detection signal of the comparator output. Prevention circuit. 5. The low input voltage malfunction with an overvoltage protection function according to claim 1, wherein a MOS transistor or a bipolar transistor having the same polarity is used for each of the first to fourth transistors. Prevention circuit.

Images