JPS5880564A - Voltage detecting circuit - Google Patents

Abstract

PURPOSE:To obtain a power voltage drop detecting circuit with low power consumption which is suitable for IC by generating reference voltage by a small number of MOS transistors (TRs) and comparing voltage to be detected with the reference voltage by a complementary MOS type differential amplifier circuit. CONSTITUTION:An active load type differential amplifier circuit 1 is composed of complementary MOS type TRs and voltage is applied to power terminals 2, 3. The gate terminal of a bias MOS TR4 is connected to a terminal 2, for example, so that the TR4 always keeps its connection status. Voltage to be detected is applied to an input terminal 5 and reference voltage to be compared is applied to an input terminal 6. An output terminal 7 outputs voltage similar to the voltage of the terminal 2 when the voltage of the terminal 5 is higher than that of the terminal 6, and outputs voltage similar to that of the terminal 3 when said condition is reversed. A voltage generating circuit 8 outputs the reference voltage to the terminal 6. A PMOSTR 9 connects gate drains in common and the gate an of NMOSTR 10 is connected to the terminal 2, for example, to keep it always at an electrically conducted state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a complementary MOS type detection circuit that can detect a drop in power supply voltage.

When this type of voltage detection circuit is used in a complementary MO8 type semiconductor integrated circuit and the reference detection voltage is configured by resistor division or the like, a high resistance is required in order to reduce power consumption. In order to realize this high resistance in, for example, an integrated circuit, it would require a very large area, which is disadvantageous. Further, the detection voltage serving as a reference can be configured by a constant voltage circuit, but the circuit configuration becomes complicated.

The present invention eliminates these drawbacks and provides a power supply voltage drop detection circuit with low power consumption by generating a reference voltage with a small number of MO8 type transistors.

Examples of the present invention will be described in detail below.

FIG. 1 shows an embodiment to which the present invention is applied, in which 1 is a well-known complementary MO8 transistor W active load type differential amplifier circuit, and 2 and 3 are power supply terminals in the circuit. . 4 is MO8 for bias in the above differential amplifier circuit.
The gate terminal of the MO8 type transistor 4 is connected to, for example, the power supply terminal 2 so that the MO8 type transistor 4 can always maintain a conductive state. Reference numeral 6.6 is an input terminal of the differential amplifier circuit, to which a voltage to be detected is applied, and to 6 a reference voltage to be compared is applied. 7 is the output terminal of the differential amplifier circuit, and when the input of terminal 6 is higher than the input of terminal 6, it outputs a voltage close to power supply terminal 2, and the input of terminal 50 is 1↓ (if lower than the input of terminal 60, Outputs a voltage close to power supply terminal 3. 8 generates a voltage that is the reference for detection,
This is a voltage generation circuit that supplies this voltage to the input terminal 6 of the differential amplifier circuit 1, and in this circuit, 9 is a gate:
A P-channel MO8 type transistor having both drain terminals connected in common, 1o is an N-channel MO8 type transistor, and this gate is provided with a DC gate bias that can maintain the MO8 type transistor 1o in a conductive state at all times. , for example, is connected to the power supply terminal 2.

According to this circuit structure 8, the reference voltage can be determined by appropriately combining the sizes of the transistors 9.10.

FIG. 2 shows another embodiment, in which elements 1 to 7 are the same as those in FIG. 1, and a circuit 8a that generates a voltage serving as a detection reference is a P-channel MO8 type transistor 1 and an N-channel MO8 type transistor 2. The gate terminal of the P-channel MO3 type transistor 1 is connected to, for example, a power supply terminal 3 so that the transistor 1 can always maintain a conductive state. The N-channel MO8 type transistor 2 has its gate and drain terminals commonly connected.

FIG. 3 shows another embodiment, in which the differential amplifier circuit 1' is different from the embodiment circuit shown in FIG.
An N-channel MO/S type transistor 4 is continuously connected between the source terminal 13 of the type bias transistor 4 and the power supply terminal 3, and a control signal is applied to the gate 17 of the transistor 4.

Further, the reference voltage generation circuit 8' also has an N-channel MO8 type transistor 16 connected in cascade between the source terminal 16 of the bias transistor 0 and the power supply terminal 3.
The same signal applied to the gate of the MO8 type transistor 14 is also applied to the gate of the transistor 16.

According to this embodiment circuit, power consumption can be reduced compared to the example shown in the first diagram. FIG. 4 shows a configuration in which a differential amplifier circuit 1' and a reference voltage generating circuit 8 are constructed by additionally incorporating the circuit configuration for reducing power consumption like the example shown in FIG. According to this, the power consumption can be further reduced than that shown in the second figure.

In each of the above-mentioned example circuits, 18.19 is an MO8 type transistor that constitutes a differential amplifier circuit, and 20.21 is an MO8 type transistor that constitutes a differential amplifier circuit.
is M acting as a load for each MO8 type transistor mentioned above.
It is an O8 type transistor. .

For devices that use small batteries as a power source, such as crystal watches, it is extremely important to keep the power consumption as low as possible. In many cases, the output is used to drive internal circuits. In order to prevent the crystal oscillation from stopping when the voltage for driving this internal circuit decreases due to a decrease in the voltage of the battery power supply, when a decrease in the power supply voltage value is detected, for example, the battery voltage is directly supplied to the internal circuit. It is necessary to provide a so-called power supply switching means.

Therefore, by combining the power supply voltage drop detection circuit of the present invention with the power supply switching means as described above, it is possible to further extend the effective life of the battery.
It is possible to facilitate maintenance of the equipment and achieve a longer lifespan.

[Brief explanation of the drawing]

Each of the circuit configurations shown in FIGS. 1 to 4 is an embodiment of the present invention, and FIG. 1 shows a complementary MO8-type reference voltage generator of an active-load type with a common source connected to the gate and drain terminals of a P-channel MO8-type transistor. A voltage detection circuit diagram in which the circuit is connected to a complementary MOS type active load type differential amplifier. Figure 2 is an active load type circuit in which the gate and drain terminals of an N-channel MO8 type transistor are connected to a complementary MO8 type reference voltage generation circuit. FIGS. 3 and 4 are voltage detection circuit diagrams using a common source circuit. FIGS. 3 and 4 are voltage detection circuit diagrams in which an MO8 type transistor for current reduction is connected. 6...Input terminal to be detected, 6...Detection reference input terminal, 7...Output terminal, 8...
Detection reference voltage generation circuit, 9...P-channel MO8 type transistor with gate and drain terminals connected, 1
0゜11...-MO8 type transistor for bias %12...N with gate and drain terminals connected
Channel MO8 type transistor, 13...MO
Source terminal of 8 type transistor 4, 14.16...
...Control MO8 type transistor, 16...Drain terminal of transistor 16, 17...Gate terminal of transistors 14 and 16, 18.19...
...N-channel MO8 type transistor, 20.21.
...P-channel MO5 type transistor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 1 Figure 2 Figure 11n /

Claims (1)

[Claims] (1) The source electrode of the conductive channel MO8 type first transistor of - is connected to one terminal of a power supply, the gate electrode and drain electrode of the first transistor are short-circuited, and the first
Another conductive channel MO8 type second transistor was connected between the drain electrode of the transistor and the other terminal of the power source, and a DC gate bias was applied to the gate electrode of the second transistor so as to make it conductive at all times. A voltage detection circuit comprising: a reference voltage generation circuit; and a complementary MO8 type differential amplifier circuit, which takes the voltage at the connection point of the two transistors as one input and applies the detected voltage to the other input. (2) The voltage detection circuit according to claim 1, wherein one or both of the reference voltage generation circuit and the differential amplifier circuit includes a cascade-sealed MOS transistor having a control input terminal.