Semiconductor equipment

Abstract

The present invention provides a semiconductor device that can reliably obtain a correct voltage detection signal when the power supply voltage is 0V or higher. [Solution] The semiconductor device 1 comprises power terminals VDD and GND, a voltage detection circuit 11, transistors 12, 13, and 14, a depletion transistor 15, a control circuit 16, input terminals 12a and 14a connected to output terminal 11b, input terminals 11a and 16b connected to power terminal VDD, source terminal 12b, input terminals 11c and 16c connected to power terminal GND, source terminals 14c and 15c, gate terminal 15a, source terminal 13b connected to drain terminal 12c, gate terminal 13a connected to drain terminal 13c, drain terminals 14b and 15b, and input terminal 16a. The control circuit 16 is configured such that even if the power supply voltage input to the voltage detection circuit 11 is less than or equal to the minimum operating voltage of the voltage detection circuit 11, the signal input to input terminal 16a of the control circuit 16 matches the potential of input terminal GND.

Description

Technical Field

[0001] The present invention relates to a semiconductor device.

Background Art

[0002] In a conventional semiconductor device, when the voltage value of the supplied power supply voltage is low, the reference voltage source in the voltage detection circuit provided in the semiconductor device may not be able to output the target voltage, and a voltage detection signal may be erroneously output. As a countermeasure in this case, an erroneous output range detection circuit capable of detecting that the voltage value of the power supply voltage is in a range where an erroneous output occurs is separately provided, and using a logic circuit, the signal output from the erroneous output range detection circuit and the voltage detection signal are logically operated to prevent an erroneous output of the voltage detection signal when the voltage value of the power supply voltage is low.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a conventional semiconductor device, generally, although the minimum operable voltage of the logic circuit is lower than that of the analog circuit, when the voltage value of the power supply voltage is extremely low, the logic circuit itself stops operating, and there is a possibility that the result of the logical operation is not correctly output.

[0005] An object of the present invention is to provide a semiconductor device that can surely obtain a correct voltage detection signal as long as the power supply voltage supplied to the semiconductor device is 0V or higher.

Means for Solving the Problems

[0006] A semiconductor device according to an embodiment of the present invention includes a voltage detection circuit that compares the potential difference input to the first input terminal and the second input terminal with a reference voltage of a predetermined potential, outputs a first level detection signal if the potential difference input to the first input terminal and the second input terminal is lower than the reference voltage of the predetermined potential, and outputs a second level detection signal if the potential difference input to the first input terminal and the second input terminal is higher than the reference voltage of the predetermined potential. A first transistor having a gate terminal connected to the output terminal of the voltage detection circuit, a source terminal connected to the first input terminal, and a drain terminal, A second transistor having a gate terminal connected to the output terminal of the voltage detection circuit, a source terminal connected to the second input terminal, and a drain terminal, A voltage drop element having a first terminal connected to the drain terminal of the first transistor and a second terminal connected to the drain terminal of the second transistor, The system includes a first terminal connected to the second terminal of the voltage drop element, and a second terminal connected to the second input terminal, and a current source that operates even when the power supply voltage is 0V. The present invention is characterized in that, even when the potential difference between the first input terminal and the second input terminal is lower than the minimum operating voltage of the voltage detection circuit, and the potential at the output terminal of the voltage detection circuit is undefined, the voltage output to the first terminal of the current source matches the potential at the second input terminal. [Effects of the Invention]

[0007] According to the present invention, if the power supply voltage supplied to the semiconductor device is 0V or higher, a correct voltage detection signal can be reliably obtained. [Brief explanation of the drawing]

[0008] [Figure 1] This is a circuit diagram showing a semiconductor device according to an embodiment of the present invention. [Figure 2]This is a circuit diagram showing a conventional semiconductor device. [Figure 3] (A) A characteristic diagram showing the relationship between the potential input to the input terminal of the control circuit and the power supply voltage in a conventional semiconductor device and (B) a semiconductor device according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, a semiconductor device according to an embodiment of the present invention will be described based on the drawings. For convenience of explanation, some components may be omitted from the illustration or the scale may be changed.

[0010] [Embodiment] Figure 1 is a circuit diagram showing a semiconductor device 1, which is an example of a semiconductor device according to this embodiment.

[0011] The semiconductor device 1 includes power terminals VDD and GND, a voltage detection circuit 11, transistors 12, 13, and 14, a depletion transistor 15, and a control circuit 16.

[0012] The voltage detection circuit 11 has an input terminal 11a connected to the power supply terminal VDD, an input terminal 11c connected to the power supply terminal GND, and an output terminal 11b. The voltage detection circuit 11 has a low voltage detection voltage VDDL set as a threshold for outputting a predetermined logic from the output terminal 11b, depending on the magnitude of the potential difference between the input terminals 11a and 11c. The voltage detection circuit 11 is configured such that when the potential difference between the input terminals 11a and 11c is greater than or equal to the minimum operating voltage VDDmin of the voltage detection circuit 11, the low voltage detection voltage VDDL is obtained as a predetermined threshold. When the potential difference between the input terminals 11a and 11c is less than or equal to the minimum operating voltage VDDmin, the potential of the output terminal 11b is undefined; when it is greater than or equal to VDDmin and less than or equal to VDDL, the potential of the output terminal 11b matches the potential of the power supply terminal VDD; and when it is greater than or equal to VDDL, it matches the potential of the power supply terminal GND.

[0013] The transistor 12 has a gate terminal 12a connected to the voltage detection circuit 11 (specifically the output terminal 11b), a source terminal 12b connected to the power supply terminal VDD, and a drain terminal 12c.

[0014] Transistor 13 has a source terminal 13b connected to transistor 12 (specifically the drain terminal 12c), a gate terminal 13a, and a drain terminal 13c, with the gate terminal 13a and the drain terminal 13c being short-circuited.

[0015] Transistor 14 has a gate terminal 14a connected to the voltage detection circuit 11 (specifically the output terminal 11b), a drain terminal 14b connected to transistor 13 (specifically the gate terminal 13a and drain terminal 13c), and a source terminal 14c connected to the power supply terminal GND.

[0016] The depletion transistor 15 has a drain terminal 15b connected to transistors 13 or 14 (specifically, gate terminal 13a and drain terminals 13c and 14b), a gate terminal 15a, and a source terminal 15c. The gate terminal 15a and the source terminal 15c are short-circuited, and even when the gate-source potential difference is zero, transistor 15 is in the ON state and operates as a current source.

[0017] The control circuit 16 has an input terminal 16a connected to the depletion transistor 15 (specifically the gate terminal 13a and drain terminals 13c, 14b, and 15b), an input terminal 16b connected to the power supply terminal VDD, and an input terminal 16c connected to the power supply terminal GND. When the potential of the input terminal 16b of the control circuit 16 is lower than a predetermined threshold which is approximately half the potential difference between the power supply terminal VDD and the power supply terminal GND, the control circuit 16 enters a standby state and its functions are limited. Conversely, when it is higher than the predetermined threshold which is approximately half, it enters an active state and its functions are unrestricted.

[0018] Next, the operation of the semiconductor device according to the embodiment of the present invention will be described by taking the semiconductor device 1 as an example. In the amplification stage composed of the transistor 12, the transistor 13, the transistor 14, and the depletion transistor 15, when the potential difference between the power supply terminal VDD and the power supply terminal GND is small and the power supply voltage is lower than the minimum operating voltage VDDmin of the voltage detection circuit 11, the potential of the output terminal 11b of the voltage detection circuit 11 becomes indeterminate. In addition, even when both the transistor 12 and the transistor 14 that constitute the amplification stage are in the OFF state and the transistor 12 cannot be turned on, since the depletion transistor 15 is in the ON state, the potential of the input terminal 16a of the control circuit 16 is fixed to GND, and the control circuit 16 surely enters the standby state. Also, when the operating voltage at which the transistors 12 and 13 can be turned on is applied while the power supply voltage is lower than the minimum operating voltage VDDmin of the voltage detection circuit 11 and the potential of the output terminal 11b is indeterminate, if the potential of the input terminal 16a of the control circuit is V16a, V16a = VDDmin - VDS12 - VDS13 ―――(1) is expressed as. Here, VDS12 is the potential difference between the drain terminal 12c and the source terminal 12b of the transistor 12, and VDS13 is the potential difference between the drain terminal 13c and the source terminal 13b of the transistor 13. VDS12 and VDS13 are determined by the current values flowing through the drain terminal 15b and the source terminal 15c of the depletion transistor 15. When V16a expressed by the formula (1) satisfies V16a = VDDmin - VDS12 - VDS13 < VDDmin / 2, the control circuit 16 enters the standby state. Therefore, if the aspect ratios (W / L) of the transistor 12, the transistor 13, and the depletion transistor 15 are determined so as to satisfy this relationship, the control circuit will not become active when the power supply voltage is lower than VDDmin.

[0019] When the potential difference between the power supply terminal VDD and the power supply terminal GND is gradually increased and exceeds the minimum operating voltage VDDmin of the voltage detection circuit 11, the potential of the output terminal 11b of the voltage detection circuit 11 coincides with the potential of the power supply terminal VDD. Generally, since the voltage detection circuit is composed of an analog circuit, the minimum operating voltage VDDmin exceeds the ON voltage of the transistor 14. In this case, both the transistor 14 and the depletion transistor 15 are in the ON state, so the input terminal 16a of the control circuit 16 is more strongly fixed to the potential of the power supply terminal GND, and the standby state is maintained.

[0020] When the potential difference between the power supply terminal VDD and the power supply terminal GND is further increased and becomes VDDL or more, the potential of the output terminal 11b of the voltage detection circuit 11 coincides with the potential of the power supply terminal GND. At this time, when VDDL is large enough to turn on both the transistor 12 and the transistor 13, V16a, which is the potential of the input terminal 16a of the control circuit 16, is represented by the above formula (1). Since the control circuit 16 becomes active when the potential of the input terminal 16a is greater than half of the potential difference between the power supply terminal VDD and the power supply terminal GND, in order to make the control circuit 16 active when the potential of the power supply terminal VDD is VDDL, the potential of the input terminal 16a needs to be V16a = VDDL - VDS12 - VDS13 > VDDL / 2. The aspect ratios (W / L) of the transistor 12, the transistor 13, and the depletion transistor 15 may be determined to satisfy this relationship.

[0021] Subsequently, the operation and effects of the semiconductor device 1 according to the present embodiment will be described while comparing with the operation of the conventional semiconductor device 2 (comparative example). FIG. 2 is a circuit diagram showing the semiconductor device 2 (comparative example).

[0022] The semiconductor device 2 (comparative example) includes a power supply terminal VDD, a power supply terminal GND, a voltage detection circuit 21, and a control circuit 22.

[0023] The voltage detection circuit 21 has an input terminal 21a connected to the power supply terminal VDD, an input terminal 21c connected to the power supply terminal GND, and an output terminal 21b. When the potential difference between the input terminals 21a and 21c is less than or equal to the minimum operating voltage VDDmin, the potential of the output terminal 21b is undefined. When it is greater than or equal to VDDmin and less than or equal to VDDL, the potential of the output terminal 21b matches the potential of the power supply terminal GND, and when it is greater than or equal to VDDL, it matches the potential of the power supply terminal VDD.

[0024] The control circuit 22 has an input terminal 22a connected to the voltage detection circuit 21 (specifically, the output terminal 21b), an input terminal 22b connected to the power supply terminal VDD, and an input terminal 22c connected to the power supply terminal GND. When the potential of the input terminal 22a of the control circuit 22 is lower than a predetermined threshold which is approximately half the potential difference between the power supply terminal VDD and the power supply terminal GND, the control circuit 22 enters a standby state and its functions are limited. Conversely, when it is higher than the predetermined threshold which is approximately half, it enters an active state and its functions are unrestricted.

[0025] Figure 3 is a characteristic diagram showing the relationship between the potential input to the input terminal of the control circuit and the power supply voltage for semiconductor device 1 and conventional semiconductor device 2 (comparative example). As shown in characteristic diagram (A) of conventional semiconductor device 2 (comparative example), when the power supply voltage input to the voltage detection circuit 21 is less than or equal to VDDmin, the potential at the input terminal 22a of the control circuit 22 is expected to be the same potential as GND. However, the operation of the analog and logic circuits constituting the voltage detection circuit 21 is unstable, causing the output terminal 21b of the voltage detection circuit 21 to enter a HiZ state, and the potential input to the input terminal 22a of the control circuit 22 becomes undefined due to the influence of external noise. When the potential at the input terminal 22a becomes undefined, the control circuit 22 can be in either a standby state or an active state, which can lead to an uncontrollable state.

[0026] On the other hand, in semiconductor device 1, due to the effect of the amplification stage composed of transistors 12, 13, 14 and depletion transistor 15, even when the power supply voltage input to the voltage detection circuit 11 is VDDmin or less, the potential of the input terminal 16a of the control circuit 16 remains fixed to GND, as shown in the characteristic diagram (B) of Figure 3. Therefore, the input terminal 16a of the control circuit 16 remains fixed to GND until the power supply voltage reaches VDDL, maintaining a standby state and enabling complete control.

[0027] As described above, with semiconductor device 1, even if the power supply voltage is below VDDmin and the potential of the output terminal 11b of the voltage detection circuit 11 is undefined, the potential of the input terminal 16a of the control circuit 16 is fixed to GND due to the effect of the amplification stage composed of transistors 12, 13, 14 and depletion transistor 15, and the control circuit 16 can be controlled as intended.

[0028] It should be noted that the present invention is not limited to the embodiments described above, and in practice, it can be implemented in various forms other than those described above, and various omissions, additions, substitutions, or modifications can be made without departing from the spirit of the invention. For example, transistor 13 may be replaced with an element that produces a voltage drop when current flows through it (such as a resistor or diode). Also, for example, depletion transistor 15 may be replaced with a current source that operates even when the power supply voltage is 0V.

[0029] Furthermore, in semiconductor device 1, the control circuit 16 is set to be active when the voltage of the signal input to the input terminal 16a of the control circuit 16 is above a predetermined threshold, which is approximately half the voltage input to the power supply terminal VDD and the power supply terminal GND, and to be in standby mode when it is below the predetermined threshold, which is approximately half. However, the control circuit may be in standby mode when the voltage input to the power supply terminal VDD and the power supply terminal GND is above half, and in active mode when it is below half. Also, the polarity of transistor 12, transistor 13 (or the element that causes a voltage drop), transistor 14 and depletion transistor 15 (or current source) may be reversed.

[0030] These embodiments and their variations are included within the scope and essence of the invention, as well as within the scope of the invention and its equivalents as described in the claims. [Explanation of Symbols]

[0031] VDD Power terminal (first input terminal) GND Power terminal (second input terminal) 11. Voltage detection circuit (voltage detection circuit) 12. Transistors (First Transistor) 13. Transistors (voltage drop elements) 14. Transistor (Second Transistor) 15. Depletion Transistor (Current Source)

Claims

1. A voltage detection circuit having a first input terminal and a second input terminal, a first input terminal connected to the first input terminal, a second input terminal connected to the second input terminal, and an output terminal, which compares the potential difference input to the first input terminal and the second input terminal with a reference voltage of a predetermined potential, and outputs a first level detection signal if the potential difference input to the first input terminal and the second input terminal is lower than the reference voltage of the predetermined potential, and outputs a second level detection signal if the potential difference input to the first input terminal and the second input terminal is higher than the reference voltage of the predetermined potential, A first transistor having a gate terminal connected to the output terminal of the voltage detection circuit, a source terminal connected to the first input terminal, and a drain terminal, A second transistor having a gate terminal connected to the output terminal of the voltage detection circuit, a source terminal connected to the second input terminal, and a drain terminal, A voltage drop element having a first terminal connected to the drain terminal of the first transistor and a second terminal connected to the drain terminal of the second transistor, The system includes a first terminal connected to the second terminal of the voltage drop element, and a second terminal connected to the second input terminal, and a current source that operates even when the power supply voltage is 0V. Even if the potential difference between the first input terminal and the second input terminal is lower than the minimum operating voltage of the voltage detection circuit, and the potential at the output terminal of the voltage detection circuit is undefined, the voltage output to the first terminal of the current source matches the potential at the second input terminal. A semiconductor device characterized by the following features.

2. The semiconductor device according to claim 1, characterized in that the voltage drop element is a resistor having a first terminal connected to the drain terminal of the first transistor and a second terminal connected to the drain terminal of the second transistor.

3. The semiconductor device according to claim 1, characterized in that the voltage drop element is a third transistor having a source terminal connected to the drain terminal of the first transistor, and a drain terminal and a gate terminal connected to the drain terminal of the second transistor.

4. The semiconductor device according to claim 1, characterized in that the voltage drop element is a diode having a first terminal connected to the drain terminal of the first transistor and a second terminal connected to the drain terminal of the second transistor.

5. The semiconductor device according to claim 1, characterized in that the current source is a depletion transistor having a drain terminal connected to a first terminal and a gate terminal and a source terminal connected to a second terminal.

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