JPH03267767A - Detecting circuit for power source voltage - Google Patents

Abstract

PURPOSE:To eliminate a temperature dependence with a desired voltage value by using plural diodes and resistors for deciding a potential value inputted to the input terminal of comparator and offsetting the threshold voltage and the temperature dependence of a shifting degree. CONSTITUTION:The potential of a 1st node 1 against power source voltage VDD has a point A which is independent of the temperature variation and this point A shifts on a broken line l by changing the shapes of an N-type MOSFET 2 (described as N-type 2 hereafter) and a resistor 3. Similarly, a point B exists in a 3rd node 7 and shifts on a broken line m according to the shapes of P-type 8 and a resistor 9. Then, by means of adequately selecting the shapes of N-type 2, P-type 8, and resistors 3, 9, the potentials of the 1st node 1 and 3rd node 7 become to have no temperature dependence when the VDD attains the desired reset release voltage. Also, by means of making the shapes of N-types 5, 2 and P-types 11, 8 to the same and adequately selecting the shapes of resistors 6, 12, the 2nd node 4 and 4th node 10 become to have no temperature dependence and to be the same potential when the VDD attains the desired reset voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power supply voltage detection circuit that detects application of a power supply voltage.

(Prior Art) In semiconductor integrated circuits, there are circuits whose operation becomes unstable when the power is turned on, so that the initial output is not determined. In some cases, it is necessary to determine the initial output of this circuit.

Figure 4 shows the MO of a power supply voltage detection circuit that supplies a control signal for output determination to a circuit having such an undetermined initial output.
This is a conventional example using a type 5 field effect transistor.

In Fig. 4, 21 and 22 are resistors, and 23 is an N-channel MO8 field effect transistor (hereinafter referred to as an N-type MO8 field effect transistor).
FET), 24 is a P-channel MO5 field effect transistor (hereinafter referred to as P-type MO5FET), 2
5 is a comparator, 251.252 is a comparator 25
253 is the output terminal of the comparator 25, 2
6 is a waveform shaping amplifier, 261 is a waveform shaping amplifier 26
This is the output terminal of

The operation of the conventional power supply voltage detection circuit configured as described above will be described below.

In FIG. 4, a resistor 21 and an N-type MOS are connected through a first node 27 between a power supply voltage VDD and a ground potential VSS.
The FET 23 is connected in series, and the resistor 22 and the P-type MO8FET 24 are connected in series via the second node 28.
The potentials of the first node 27 and the second node 28 are supplied to input terminals 251 and 252 of the comparator 25, respectively.

FIG. 5 shows the temperature dependence of each input terminal voltage on the power supply voltage. When the power supply voltage VDD is increased and reaches a certain value (hereinafter referred to as reset release voltage), the input is input to the input terminal 252 of the comparator 25. The voltage value of the signal becomes larger than the voltage value of the signal input to the input terminal 251,
The output value of the comparator 25 changes. The output signal is amplified by the amplifier 26 and output from the output terminal 261. By applying the power supply voltage, a reset signal is applied to each circuit in the semiconductor device to determine the initial output, and output terminal 2
The reset is canceled by the change in the output of 61.

(Problems to be Solved by the Present Invention) In the conventional configuration, as shown in FIG. 5, the voltage values input to the input terminals 251 and 252 of the comparator have points C and D that have no temperature dependence, respectively. be.

The point C can be set at a desired potential on the broken line p in FIG. 5 by changing the shapes of the N-type MOSFET 23 and the resistor 21. Also, the light is P type MO8FET2
By changing the shapes of resistor 4 and resistor 22, a desired potential on the broken line q in FIG. 5 can be set. Therefore, if the dot coincides with the point C at the intersection of the broken line p and the broken line q, the reset release voltage value will no longer have temperature dependence.

However, the intersection of the broken line p and the broken line q is the N-type MOSFET2.
3, and does not depend on the shapes of the P-type MO8FET 24 and the resistors 21 and 22. Therefore, it is impossible to eliminate temperature dependence at a desired reset release voltage value.

The present invention solves the above problem, and aims to eliminate temperature dependence at a desired reset release voltage value.

(Means for Solving the Problems) To achieve this object, the power supply voltage detection circuit of the present invention uses a plurality of diodes and resistors to determine the voltage value input to the input terminal of the comparator. The configuration is such that the temperature dependence of threshold voltage and the temperature dependence of mobility are offset.

(Function) With this configuration, the input terminal voltage of the comparator has no temperature dependence at a desired power supply voltage value, and the reset pulse, which is the comparator output, also has no temperature dependence.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows an embodiment of the present invention, in which a MOSFET whose drain and gate are connected is used as the diode means.

In FIG. 1, an N-type MO8FET 2 and a resistor 3 are connected in series between the power supply voltage VDD and the ground potential ■sS via a first node 1, and an N-type MO8FET 2 and a resistor 3 are connected in series via a second node 4.
Connect ET5 and resistor 6 in series, and connect through the third node 7.
A cp-type MO8FET 8 and a resistor 9 are connected in series, and a p-type MO8FET II and a resistor 12 are connected via a fourth node 1o.
are connected in series, the first node 1 is connected to the gate of N-type MO8FET5, and the third node 7 is connected to P-type MO8FET5.
Tl1 (7) gate, the second node 4 is connected to the input terminal 131 of the comparator 13, the fourth node 1o is connected to the input terminal 132 of the comparator 13, and the comparator result is passed through the waveform shaping amplifier 14. It is a composition that will come out.

FIG. 2 shows the temperature dependence of the potentials of the first node 1 and the third node 7 with respect to the power supply voltage.

FIG. 3 shows the temperature dependence of each input terminal voltage of the comparator 13.

The operation of the power supply voltage detection circuit of the present invention will be described below with reference to FIGS. 1, 2, and 3.

Until the power supply voltage VDD reaches the threshold voltage of the MOSFET from the ground potential, the N-type MO8FET 2 is in a non-conductive state and the potential of the first node 1 is the power supply voltage VDD. Furthermore, the N-type MO8FET 5 also becomes non-conductive and the second node 4
The potential of is also the power supply voltage VDD. In addition, P-type MO8FE
T8 becomes non-conductive, and the potential of the third node 7 is the ground potential. Further, the P-type MO8FET II also becomes non-conductive, and the potential of the fourth node 10 is also at the ground potential.

When the power supply voltage VDD becomes equal to or higher than the threshold voltage of the MOSFET, the N-type MO8FET2 becomes conductive, and the resistor 3
A potential divided by the saturation characteristics of the N-type MO8FET 2 is output to the first node 1. Furthermore, N-type MO5F
ET5 also becomes conductive, and resistor 6 and N-type MO8FET
The voltage divided by the saturation characteristic of 5 is output to the second node 4. On the other hand, the P-type MO5FET 8 also becomes conductive at the same time, and a potential divided by the saturation characteristics of the resistor 9 and the P-type MO8FET 8 is output to the third node 7.

Furthermore, the P-type MO5FETII also becomes conductive, and the voltage divided by the saturation characteristics of the resistor 12 and the P-type MO8FETII is output to the fourth node 10.

The potential of the first node 1 with respect to the power supply voltage VDD has a point A that does not depend on temperature changes as shown in FIG.
If the shapes of the N-type MO5FET 2 and the resistor 3 are changed, it will move on the broken line Q in FIG. On the other hand, regarding the third node 7, there is a point B that is similarly independent of temperature changes, and this point B moves on the broken line m in FIG. 2 due to the shapes of the P-type MO8FET 8 and the resistor 9.

Therefore, by appropriately selecting the shapes of the N-type MO8FET 2.8 and the resistor 3.9, the potentials of the first node 1 and the third node 7 can be adjusted when the power supply voltage VDD reaches the desired reset release voltage. Make it independent of temperature. Also, N-type MO5FET5 is replaced with N-type MO5FET5.
Same shape as 2, P type MO8FETII is replaced with P type MO3
By using the same shape as FET 8 and appropriately selecting the shapes of resistors 6 and 12, when the power supply voltage VDD reaches the desired reset voltage, the second node 4 and the fourth node 1
0 is the same potential without temperature dependence.

Further, when the power supply voltage VDD exceeds the desired reset release voltage value, the input terminals 131 and 132 of the comparator 13
The magnitude relationship of the potentials is reversed. The output of the comparator 13 outputs a reset pulse during the period from when the power supply voltage is applied until it reaches the reset release voltage. This output is waveform-shaped by a waveform-shaping amplifier 26, and a reset signal is transmitted from the output to other circuits.

Incidentally, in the above embodiment, a MOSFET is used as the diode means.
However, a bipolar transistor connected to operate as a diode may also be used.

(Effects of the Invention) As explained above, according to the present invention, in a power supply voltage detection circuit that outputs a control signal to a circuit network based on the power supply voltage, the reset release voltage value can be determined according to specifications, and is temperature-dependent. The practical effect is great.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power supply voltage detection circuit in an embodiment of the present invention, FIG. 2 is a characteristic diagram of a node potential in an embodiment of the present invention, and FIG. 3 is a power supply voltage detection circuit in an embodiment of the present invention. A characteristic diagram showing the relationship between the voltage value input to the comparator input terminals 131 and 132 of the circuit and the power supply voltage. Figure 4 is a circuit diagram of a conventional power supply voltage detection circuit. Figure 5 is a conventional power supply voltage detection circuit. FIG. 3 is a characteristic diagram showing the relationship between the voltage value input to the comparator input terminal of the power supply voltage and the power supply voltage. 1...first node, 2,5...-N type M○5FE
T, 3, 6, 9. 12...Resistor, 4...Second node, 7...Third node. 10... Fourth node, 8.11... P-type MO
3FET, 13... Comparator, 131°1
32... Input terminal, 14... Waveform shaping amplifier.

Claims (2)

[Claims] (1) A first diode means connected in the forward direction between one power supply terminal and a first node, and a first resistor connected between the first node and the other power supply terminal. means, a first active element connected in a forward direction between the one power supply terminal and the second node, and a first active element connected between the second node and the other power supply terminal. a third resistance means connected between the one power supply terminal and the third node; and a second resistance means connected between the third node and the other power supply terminal. a fourth resistor connected between the one power supply terminal and the fourth node; and a second resistor connected between the fourth node and the other power supply terminal. A power supply voltage detection circuit comprising: diode means; and means for detecting coincidence of potentials of the second node and the fourth node. (2) When the power supply voltage reaches the desired potential, the second
The first diode means, the second diode means, and the first diode means, so that the potential of the node and the potential of the fourth node are the same potential and have no temperature dependence. the shape of the second diode means;
and the first resistance means, the second resistance means,
2. The power supply voltage detection circuit according to claim 1, wherein the resistance values of the third resistance means and the fourth resistance means are selected.