Semiconductor Integrated Circuit

Abstract

To determine current at low cost and high accuracy using a resistor formed in a semiconductor integrated circuit and using the operation of an existing transistor.SOLUTION: A current driving circuit includes a first transistor that extracts current from a voltage line in accordance with a control signal, and outputs data as a voltage change of the voltage line. A current detection circuit that detects current to be supplied to the voltage line includes a first resistor element and a second resistor element with the same resistance value that are connected to the voltage line, a second transistor connected to the first resistor element, having the size of 1 / N of the first transistor, and receiving the control signal at a gate, a current source connected to the second resistor element and supplying a reference current that is 1 / N of the desired current to be supplied to the voltage line, and a comparator that determines whether the desired current is supplied to the voltage line by comparing the voltage of the first resistor element and the voltage of the second resistor element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor integrated circuit. [Background technology]

[0002] An abnormality monitoring circuit has been proposed that monitors whether a reference voltage generated by a reference voltage circuit is normal by comparing the reference voltage with a threshold voltage generated based on a reference current generated by a reference current circuit (see, for example, Patent Document 1).

[0003] Also, a method is known in which a parent unit detects a transmission current from a child unit such as a fire detector by using a power supply line that connects the child unit and a parent unit such as a receiver. For example, the parent unit generates a reference voltage based on a load current that flows during an idle timing when no transmission current flows, and detects the transmission current by comparing the generated reference voltage with a voltage generated based on the transmission current using a comparator (for example, see Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-207201 A [Patent Document 2] International Publication No. 2010 / 038480 [Patent Document 3] International Publication No. 2010 / 038476 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, whether or not a current such as a power supply current supplied to a load circuit is sufficient is determined, for example, by converting the current into a voltage using a resistor and comparing the converted voltage with a reference voltage. When a resistor for voltage conversion is formed within a semiconductor integrated circuit, the resistance value varies due to fluctuations in the semiconductor manufacturing process, and the accuracy of the comparison with the reference voltage decreases. When an external component such as a shunt resistor is used, the variation in resistance is reduced, and the accuracy of the comparison with the reference voltage improves. However, when an external component is used, costs increase and reliability decreases.

[0006] The disclosed technology has an object to determine current at low cost and with high accuracy by utilizing the operation of existing transistors in a semiconductor integrated circuit and using resistors formed in the semiconductor integrated circuit. [Means for solving the problem]

[0007] In order to solve the above technical problem, a semiconductor integrated circuit according to one aspect of the present invention comprises: connected to an input / output terminal connectable to a power supply terminal that supplies a voltage to the voltage line; Depending on the control signal received at the gate, The above a first transistor for sinking current from a voltage line; When the power supply terminal is connected to the input / output terminal, Data is output as a change in the voltage on the voltage line. It is possible A semiconductor integrated circuit having a current driver circuit and a current detection circuit that detects a current supplied to the voltage line, the current detection circuit comprising: The voltage line between the power supply terminal and the current drive circuit has one end The voltage supply circuit includes a first resistor element and a second resistor element connected to each other and having the same resistance value; a second transistor connected to the other end of the first resistor element, having a transistor size that is 1 / N of the size of the first transistor, and receiving the control signal at its gate; a current source connected to the other end of the second resistor element and supplying a reference current that is 1 / N of a desired current to be supplied to the voltage line; and a comparator that determines whether the desired current is being supplied to the voltage line by comparing the voltage at the other end of the first resistor element received at a first input with the voltage at the other end of the second resistor element received at a second input. Effect of the Invention

[0008] By utilizing the operation of existing transistors in a semiconductor integrated circuit, current can be determined at low cost and with high accuracy using resistors formed within the semiconductor integrated circuit. [Brief description of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing a first embodiment of a semiconductor integrated circuit according to the present invention. [Diagram 2] 2 is a waveform diagram showing an example of the operation of the semiconductor integrated circuit of FIG. [Diagram 3] FIG. 2 is a circuit diagram showing a second embodiment of a semiconductor integrated circuit according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described with reference to the drawings. In the following, the same reference numerals as the voltage or current names are used for voltage lines, terminals, and nodes through which voltages are transmitted, and the same reference numerals as the signal names are used for signal lines, terminals, and nodes through which signals are transmitted. In each drawing, the same reference numerals are used for the same components, and duplicated explanations may be omitted.

[0011] (First embodiment of semiconductor integrated circuit) FIG. 1 is a circuit diagram showing a first embodiment of a semiconductor integrated circuit of the present invention. The semiconductor integrated circuit 100 shown in FIG. 1 has a transmission circuit 110 and a control circuit 120. The transmission circuit 110 has a current driving circuit 10 and a current detection circuit 20. For example, the semiconductor integrated circuit 100 operates with a power supply voltage VCC supplied from a parent device (not shown) via a power supply line VCC, and has a function of transmitting information such as data DATA to the parent device using a change in the voltage of the power supply line VCC. Information such as data DATA is transmitted to the parent device using a potential difference between the power supply voltage VCC that is lowered by drawing a current from the power supply line VCC and the power supply voltage VCC when no current is drawn from the power supply line VCC. That is, the semiconductor integrated circuit 100 outputs data as a change in the voltage of the power supply line VCC. The power supply line VCC is an example of a voltage line.

[0012] The current driver 10 includes resistor elements R11 and R12, inverters IV11 and IV12, n-channel transistors NM11, NM12, and NM13, a reference voltage generator 12, and an amplifier AMP1. The current detector 20 includes resistor elements R13 and R14, an n-channel transistor NM14, a current source CS1, and a comparator CMP1. The n-channel transistor NM13 is an example of a first transistor, and the n-channel transistor NM14 is an example of a second transistor. The resistor element R13 is an example of a first resistor element, and the resistor element R14 is an example of a second resistor element. Hereinafter, the n-channel transistors are also simply referred to as transistors. The n-channel transistors NM11 and NM12 are examples of switches. Instead of the n-channel transistors NM11 and NM12, switches that turn on (conduct) when a high level is received at the control terminal may be provided. Also, instead of the n-channel transistors NM11 and NM12, variable resistor elements whose resistance value changes according to the voltage received at the control terminal may be provided.

[0013] In the current driver 10, an inverter IV11 outputs an active signal ACTH obtained by inverting the logic of data DATA. An inverter IV12 outputs an active signal ACTL obtained by inverting the logic of the active signal ACTH. The active signal ACTH is output to an amplifier AMP1, and the active signal ACTL is supplied to the gate of a transistor NM12.

[0014] The active signals ACTH and ACTL are set to high and low levels, respectively, in response to the low level of the data DATA when a current is drawn from the power supply line VCC by the current drive circuit 10. The active signals ACTH and ACTL are set to low and high levels, respectively, in response to the high level of the data DATA when no current is drawn from the power supply line VCC.

[0015] The resistor elements R11, R12 and the transistor NM11 are connected in series between the power supply line VCC and the ground line GND. The transistor NM11 is turned on while the active signal ACTH is at a high level. When the transistor NM11 is on, a divided voltage DIV1 obtained by dividing the power supply voltage VCC is generated at the connection node DIV1 between the resistor elements R11 and R12. That is, the resistor elements R11 and R12 operate as a voltage divider circuit. When the transistor NM11 is off, the divided voltage DIV1 is set to the power supply voltage VCC.

[0016] The reference voltage generating circuit 12 generates a reference voltage VREF, which is the low level value of the power supply voltage VCC when current is drawn from the power supply voltage VCC. The reference voltage VREF is set to a value shown in equation (1) with respect to the low level value of the power supply voltage VCC supplied from the parent device. In equation (1), symbols R11 and R13 indicate the resistance values ​​of the resistive elements R11 and R12, respectively. VREF = (low-level value of power supply voltage VCC) × R12 / (R11 + R12) (1)

[0017] The amplifier AMP1 operates when it receives a high-level active signal ACTH and stops operating when it receives a low-level active signal ACTH. The amplifier AMP1 differentially amplifies the reference voltage VREF received at its - input and the divided voltage DIV1 received at its + input. The amplifier AMP1 increases the control voltage AOUT1 the higher the divided voltage DIV1 is than the reference voltage VREF, and decreases the control voltage AOUT1 the lower the divided voltage DIV1 is than the reference voltage VREF. The control voltage AOUT1 is supplied to the gates of the transistors NM13 and NM14.

[0018] The transistor NM12 is connected between the control line AOUT1 and the ground line GND. The transistor NM12 is turned on when it receives an active signal ACTL at a high level, and is turned off when it receives an active signal ACTL at a low level.

[0019] The transistor NM13 has a drain connected to the serial input / output terminal SIO, a source connected to a ground line GND, and a gate receiving a control signal AOUT1. The serial input / output terminal SIO is connected to a power supply line VCC via a resistor element R15 arranged outside the semiconductor integrated circuit 100. The serial input / output terminal SIO is a terminal for drawing current from the power supply line VCC by the current drive circuit 10 when data DATA is at a low level.

[0020] Next, the operation of the current driver 10 will be described. When the data DATA is at a high level, the transistor NM11 is turned off by a low-level active signal ACTH, and the amplifier AMP1 stops operating. When the data DATA is at a high level, the transistor NM12 is turned on by a high-level active signal ACTL, and the gate of the transistor NM13 is set to a low level, turning the transistor NM13 off. This causes the current driver 10 to stop operating.

[0021] On the other hand, when the data DATA is at low level, the transistor NM11 is turned on by a high level active signal ACTH, the divided voltage DIV1 is generated, and the amplifier AMP1 operates. Also, when the data DATA is at low level, the transistor NM12 is turned off by a low level active signal ACTL. This causes the transistor NM13 to draw current from the power supply line VCC via the serial input / output terminal SIO in response to the control signal AOUT1 from the amplifier AMP1 received at its gate. Then, the power supply line VCC is set to a low level value.

[0022] As a result, the parent device that supplies the power supply voltage VCC to the semiconductor integrated circuit 100 can receive the data DATA from the semiconductor integrated circuit 100 by detecting a drop in the power supply voltage VCC.

[0023] In the current detection circuit 20, the resistor element R13 and the transistor NM14 are connected in series between the power supply line VCC and the ground line GND. The transistor NM14 operates in response to a control signal AOUT1. For example, the gate width of the transistor NM14 is set to 1 / N of the gate width of the transistor NM13. That is, the symbol N indicates the ratio W13 / W14 of the gate width W13 of the transistor NM13 to the gate width W14 of the transistor NM14. For example, "N" is 200, but may be 100 or 50. The element size and element structure of the transistor NM14 are the same as those of the transistor NM13, except for the gate width. The gate width is an example of a transistor size.

[0024] Therefore, in response to a control signal AOUT1 from the amplifier AMP1, the current flowing between the source and drain of the transistor NM14 can be made 1 / N of the current flowing between the source and drain of the transistor NM13.

[0025] The transistors NM13 and NM14 are formed adjacent to each other on the semiconductor substrate on which the semiconductor integrated circuit 100 is formed. Therefore, even if the semiconductor manufacturing process for manufacturing the semiconductor integrated circuit 100 varies, the size ratio of the transistors NM13 and NM14 can be kept constant. Furthermore, the electrical characteristics of the transistors NM13 and NM14 formed on the same semiconductor substrate change in the same manner in response to temperature changes in the semiconductor substrate. As a result, the current ratio of the transistors NM13 and NM14 can be set with high accuracy.

[0026] The resistor element R14 and the current source CS1 are connected in series between the power supply line VCC and the ground line GND. The resistance value of the resistor element R14 is set to the same value as the resistance value of the resistor element R13. For example, the resistor elements R13 and R14 are formed as diffusion layer resistors by utilizing a diffusion layer formed on a semiconductor substrate. At this time, the resistor elements R13 and R14 are formed at positions adjacent to each other on the semiconductor substrate. Therefore, even if the semiconductor manufacturing process for manufacturing the semiconductor integrated circuit 100 varies, the shapes (length, width, thickness) of the resistor elements R13 and R14 can be made the same, and the resistance values ​​of the resistor elements R13 and R14 can be made the same.

[0027] The current source CS1 operates when the active signal ACTH is at a high level, and draws in the reference current IREF from the power supply line VCC via the resistor element R14. The current source CS1 stops operating when the active signal ACTH is at a low level, and stops drawing the reference current IREF from the power supply line VCC via the resistor element R14. The inverters IV11 and IV12 that generate the active signals ACTH and ACTL, and the transistors NM11 and NM12 are an example of an operation control circuit that stops the operation of the current driver 10 and the current source CS1 when low-level data is not output to the power supply line VCC.

[0028] The current source CS1 is designed to pass a reference current IREF which is 1 / N of a desired current supplied to the power line VCC. The current source CS1 may also be designed to pass a reference current IREF which is 1 / N of a design value of a current I1 which the transistor NM13 draws from the power line VCC in response to low-level data DATA. Here, the design value of the current I1 is the current I1 which the transistor NM13 draws from the power line VCC when the current supplied from the source of the power voltage VCC via the power line VCC is in a typical state.

[0029] In this embodiment, since the current flowing between the source and drain of the transistor NM14 and the current flowing through the current source CS1 can be made small, the increase in current consumption when the current detection circuit 20 is added to the transmission circuit 110 can be minimized.

[0030] The negative input of the comparator CMP1 is connected to a connection node Va between the resistor element R13 and the transistor NM14. The positive input of the comparator CMP1 is connected to a connection node Vb between the resistor element R14 and the current source CS1. The voltage Va at the connection node Va is expressed by equation (2), and the voltage at the connection node Vb is expressed by equation (3). Va=VCC-(R13×I2)=VCC-(R13×I1 / N) ‥(2) Vb = VCC - (R14 × IREF) ... (3) In the equations (2) and (3), the symbols R13 and R14 indicate the resistance values ​​of the resistive elements R13 and R14, respectively.

[0031] Comparator CMP1 compares voltage Va received at its - input with voltage Vb received at its + input to determine the magnitude of the current supplied to the power supply line VCC. For example, comparator CMP1 outputs a low-level comparison result signal CMP when voltage Va is greater than voltage Vb, i.e., when current I2 is less than reference current IREF. Comparator CMP1 outputs a high-level comparison result signal CMP when voltage Va is equal to or less than voltage Vb, i.e., when current I2 is equal to or greater than reference current IREF. When current source CS1 is not operating, voltages Va and Vb are set to high levels, so comparator CMP1 outputs a high-level comparison result signal CMP.

[0032] The current source CS1 is designed to pass a reference current IREF that is, for example, 1 / N of the minimum power supply current, which is the minimum value of the power supply current required for normal operation of the control unit 120. When the power supply current supplied from the parent device via the power supply terminal VCC is smaller than the minimum power supply current, the current I2 is smaller than the reference current IREF, and the voltage Va is larger than Vb. On the other hand, when the power supply current supplied from the parent device to the power supply terminal VCC is equal to or larger than the minimum power supply current, the current I2 is equal to or larger than the reference current IREF, and the voltage Va is equal to or smaller than Vb.

[0033] In this way, the current detection circuit 20 detects whether the power supply current from the parent device is smaller than the minimum power supply current by utilizing the operation of the transistor NM13 of the current drive circuit 10 as the child device. At this time, the current I2 corresponding to the current I1 can be detected with high accuracy without attaching a highly accurate shunt resistor for detecting the current externally to the semiconductor integrated circuit 100. Since the number of components externally attached to the semiconductor integrated circuit 100 can be reduced, the cost of a system (e.g., a child device) including the semiconductor integrated circuit 100 can be reduced, and the reliability of the system including the semiconductor integrated circuit 100 can be improved.

[0034] The control unit 120 includes various circuits that realize the functions of the semiconductor integrated circuit 100 as a child device, and functional units such as an LED driver that drives components such as an LED (Light Emitting Diode) (not shown). For example, when the comparison result signal CMP is at a high level, the control unit 120 determines that the supply of power supply current from the parent device is sufficient, and operates all the circuits and functional units in the control unit 120.

[0035] On the other hand, when the comparison result signal CMP is at a low level, the control unit 120 determines that the supply of power supply current from the parent unit is insufficient, and stops the operation of at least a part of the functional units in the control unit 120 (e.g., an LED driver). When the comparison result signal CMP is at a low level, the control unit 120 may stop the functions of not only the functional units but also at least a part of the circuits in the control unit 120. By stopping the operation of the functional units or a part of the circuits, the power consumption of the control unit 120 can be reduced. As a result, even when the supply of power supply current from the parent unit is insufficient, the circuits necessary for realizing the functions of the child unit can be operated.

[0036] Fig. 2 is a waveform diagram showing an example of the operation of the semiconductor integrated circuit 100 of Fig. 1. For example, the semiconductor integrated circuit 100 transmits data DATA to the parent device using the power line VCC during a standby period in which the control unit 120 is not operating. For example, the semiconductor integrated circuit 100 transmits data alternately at a predetermined cycle between a standby period and an operating period in which the control unit 120 operates. Note that the semiconductor integrated circuit 100 may transmit data DATA during periods other than the standby period.

[0037] When transmitting data DATA to the parent device, the semiconductor integrated circuit 100 alternately changes the logic level of the data DATA between high and low levels. When the data DATA changes from high to low, the current driver 10 starts operating, and the transistor NM13 operates as described above. Then, the transistor NM13 draws current from the power line VCC, causing the power supply voltage VCC to change from a high level (e.g., 24 V) to a low level (e.g., 6 V). The parent device receives the data DATA transmitted from the child device, the semiconductor integrated circuit 100, in response to the change in the power supply voltage VCC.

[0038] For example, if the supply of power current from the parent device is insufficient, the current I2 flowing through transistor NM14 corresponding to the current I1 (drawn current) flowing through transistor NM13 becomes smaller than the reference current IREF. As a result, the voltage Va supplied to the - input of comparator CMP1 becomes higher than the voltage Vb supplied to the + input of comparator CMP1, and the comparator CMP1 outputs a low-level comparison result signal CMP.

[0039] On the other hand, when the supply of power current from the parent device is sufficient, the current I2 flowing through transistor NM14 becomes larger than the reference current IREF, the voltage Va is lower than the voltage Vb, and the comparator CMP1 outputs a high-level comparison result signal CMP.

[0040] As described above, in this embodiment, since the transistors NM13 and NM14 are formed at positions adjacent to each other on the semiconductor substrate, the size ratio of the transistors NM13 and NM14 can be kept constant even if the semiconductor manufacturing process varies. In addition, the electrical characteristics of the transistors NM13 and NM14 can be changed in a similar manner in response to temperature changes in the semiconductor substrate. Therefore, the current ratio of the transistors NM13 and NM14 can be set with high accuracy. In addition, since the resistor elements R13 and R14, which are set to the same resistance value, are formed at positions adjacent to each other on the semiconductor substrate, the resistance values ​​of the resistor elements R13 and R14 can be made the same even if the semiconductor manufacturing process varies.

[0041] Therefore, without attaching a highly accurate shunt resistor externally to the semiconductor integrated circuit 100, a current I2 that is 1 / N of the current I1 can be detected with high accuracy and supplied to the comparator CMP1 as a voltage Va, and a voltage Vb corresponding to the reference current IREF can be generated. As a result, the number of components attached externally to the semiconductor integrated circuit 100 can be reduced, and the cost of a system (e.g., a child device) including the semiconductor integrated circuit 100 can be reduced. Furthermore, since the number of components can be reduced, the reliability of the system including the semiconductor integrated circuit 100 can be improved.

[0042] The magnitude of the power supply current supplied to the power supply terminal VCC can be determined by using the transistor NM13 of the current driver circuit 10, which transmits information such as data DATA to the parent device by utilizing the change in the voltage of the power supply line VCC. This allows the circuit scale of the current detection circuit 20 to be reduced.

[0043] When it is determined that the power supply current is insufficient, the functions of at least some of the circuits in the control unit 120 are stopped, thereby reducing the power consumption of the control unit 120. As a result, even when the supply of power supply current from the parent unit is insufficient, the circuits necessary to realize the functions of the child unit can be operated.

[0044] By operating the current source CS1 only during the period when data DATA is transmitted to the parent device and determining whether the power supply current is sufficient, the increase in power consumption of the semiconductor integrated circuit 100 can be minimized even when the current detection circuit 20 is provided.

[0045] (Second embodiment of semiconductor integrated circuit) 3 is a circuit diagram showing another embodiment of a semiconductor integrated circuit. Detailed description of elements similar to those of the semiconductor integrated circuit 100 shown in FIG. 1 will be omitted. The semiconductor integrated circuit 102 shown in FIG. 3 has a current detection circuit 30 and a regulator 40. The semiconductor integrated circuit 102 generates an output voltage VOUT from an input voltage VIN, and outputs the generated output voltage VOUT to a current load circuit 200 via an output terminal VOUT as a power supply voltage. The semiconductor integrated circuit 102 also outputs a comparison result signal CMP indicating a current supply capability by the output voltage VOUT to the current load circuit 200. Although not particularly limited, for example, the output voltage VOUT is a power supply voltage that operates the current load circuit 200. Then, a power supply current is supplied to the current load circuit 200 via a voltage terminal VOUT.

[0046] The current detection circuit 30 includes a p-channel transistor PM21, a current source CS2, resistor elements R21 and R22, a comparator CMP2, and a buffer BUF. The regulator 40 includes a reference voltage generation circuit 42, an amplifier AMP2, a p-channel transistor PM22, and resistor elements R23 and R24. The p-channel transistor PM22 is an example of a first transistor, and the p-channel transistor PM21 is an example of a second transistor. The resistor element R21 is an example of a first resistor element, and the resistor element R22 is an example of a second resistor element. Hereinafter, the p-channel transistor is also simply referred to as a transistor.

[0047] In the regulator 40, the resistor elements R23 and R24 are connected in series between the output voltage line VOUT and the ground line GND, and a divided voltage DIV2 obtained by dividing the output voltage VOUT is generated at the connection node of the resistor elements R23 and R24. The reference voltage generating circuit 42 generates a reference voltage VREF having the same value as the divided voltage DIV2 when the output voltage VOUT is at the expected value. The ground line GND is an example of a low voltage line that is set to a voltage lower than the input voltage VIN.

[0048] The amplifier AMP2 receives the reference voltage VREF at its negative input and the divided voltage DIV2 at its positive input. The amplifier AMP2 increases the control voltage AOUT2 as the divided voltage DIV2 is higher than the reference voltage VREF, and decreases the control voltage AOUT2 as the divided voltage DIV1 is lower than the reference voltage VREF.

[0049] The control voltage AOUT2 is supplied to the gates of the transistors PM21 and PM22. The transistor PM22 is connected between the input voltage line VIN and the output voltage line VOUT. In this way, the transistor PM22 generates the output voltage VOUT by causing a current I1 to flow in response to a control signal AOUT2 received at its gate from the amplifier AMP2, and supplies the output voltage VOUT to the current load circuit 200 via the output terminal VOUT as a power supply current.

[0050] In the current detection circuit 30, the transistor PM21 and the resistor element R21 are connected in series between the input voltage line VIN and the ground line GND. The transistor PM21 operates in response to a control signal AOUT2. For example, the transistor PM21 is set to 1 / N of the gate width of the transistor PM22. For example, "N" is 200, but may be 100 or 50. The element size and element structure of the transistor PM21 are the same as those of the transistor PM22, except for the gate width.

[0051] Therefore, in response to a control signal AOUT2 from the amplifier AMP2, the current flowing between the source and drain of the transistor PM21 can be made 1 / N of the current flowing between the source and drain of the transistor PM22.

[0052] The transistors PM21 and PM22 are formed adjacent to each other on the semiconductor substrate on which the semiconductor integrated circuit 100 is formed. Therefore, even if the semiconductor manufacturing process for manufacturing the semiconductor integrated circuit 100 varies, the size ratio of the transistors PM21 and PM22 can be kept constant. Furthermore, the electrical characteristics of the transistors PM21 and PM22 formed on the same semiconductor substrate change in a similar manner in response to temperature changes in the semiconductor substrate. As a result, the current ratio of the transistors PM21 and PM22 can be set with high accuracy.

[0053] The current source CS2 and the resistor element R22 are connected in series between the input voltage line VIN and the ground line GND. The resistance value of the resistor element R22 is set to the same value as the resistance value of the resistor element R21. For example, the resistor elements R21 and R22 are formed by utilizing a diffusion layer formed on a semiconductor substrate. Since the resistor elements R21 and R21 are formed at positions adjacent to each other on the semiconductor substrate, the resistance values ​​of the resistor elements R21 and R22 can be made the same even if the semiconductor manufacturing process fluctuates.

[0054] The current source CS2 draws a reference current IREF from an input voltage line VIN to which the input voltage VIN is supplied from a source of the input voltage VIN. The current source CS2 is designed to draw a reference current IREF that is, for example, 1 / N of the desired current supplied to the input voltage line VIN.

[0055] In this embodiment, the current flowing between the source and drain of the transistor PM21 and the current flowing through the current source CS2 can be reduced, so that the increase in current consumption when the current detection circuit 30 is added to the semiconductor integrated circuit 102 can be minimized.

[0056] The + input of comparator CMP2 is connected to connection node Va between transistor PM21 and resistor element R21. The - input of comparator CMP2 is connected to connection node Vb between current source CS2 and resistor element R22. The voltage Va at connection node Va is represented by Equation (4), and the voltage at connection node Vb is represented by Equation (5). Va = R21 × I2 = R21 × I1 / N ‥(4) Vb = R22 × IREF ‥(5) In Equations (4) and (5), the symbols R21 and R22 represent the resistance values of resistor elements R21 and R22, respectively.

[0057] Comparator CMP2 determines the magnitude of the current supplied to input voltage line VIN by comparing the voltage Va received at the + input with the voltage Vb received at the - input. Comparator CMP2 outputs a high-level comparison result signal CMP when voltage Va is greater than voltage Vb, that is, when current I2 is greater than reference current IREF. Comparator CMP2 outputs a low-level comparison result signal CMP when voltage Va is less than or equal to voltage Vb, that is, when current I2 is less than reference current IREF.

[0058] As described above, current source CS2 is designed to conduct a reference current IREF that is one Nth of the desired current supplied to input voltage line VIN. Therefore, when current I1 is less than the desired current, current I2 < reference current IREF, and voltage Va < Vb. On the other hand, when current I1 is greater than or equal to the desired current, current I2 ≧ reference current IREF, and voltage Va ≧ Vb.

[0059] In this way, the current detection circuit 30 detects whether the current I1 supplied to the current load circuit 200 is smaller than the desired current by utilizing the operation of the transistor PM22 of the regulator 40. At this time, similar to the first embodiment, the current I2 corresponding to the current I1 can be detected with high accuracy without externally attaching a highly accurate shunt resistor for detecting the current to the semiconductor integrated circuit 102. Since the number of components externally attached to the semiconductor integrated circuit 102 can be reduced, the cost of a system including the semiconductor integrated circuit 102 can be reduced, and the reliability of the system including the semiconductor integrated circuit 102 can be improved.

[0060] When the comparison result signal CMP is at a high level, the current load circuit 200 determines that the power supply current supplied from the regulator 40 is sufficient, and operates all the circuits in the current load circuit 200. On the other hand, when the comparison result signal CMP is at a low level, the current load circuit 200 determines that the power supply current supplied from the regulator 40 is not sufficient, and stops the function of at least some of the circuits in the current load circuit 200. As a result, even when the power supply current supplied from the regulator 40 is not sufficient, it is possible to operate the minimum number of circuits necessary to realize the function of the current load circuit 200.

[0061] As described above, in this embodiment, since the transistors PM21 and PM22 are formed at positions adjacent to each other on the semiconductor substrate, the size ratio of the transistors PM21 and PM22 can be kept constant even if the semiconductor manufacturing process varies. In addition, the electrical characteristics of the transistors PM21 and PM22 can be changed in a similar manner in response to temperature changes in the semiconductor substrate. Therefore, the current ratio of the transistors PM21 and PM22 can be set with high accuracy. In addition, since the resistive elements R21 and R22, which are set to the same resistance value, are formed at positions adjacent to each other on the semiconductor substrate, the resistance values ​​of the resistive elements R21 and R22 can be made the same even if the semiconductor manufacturing process varies.

[0062] Therefore, without externally attaching a highly accurate shunt resistor to the semiconductor integrated circuit 102, a current I2 that is 1 / N of the current I1 can be detected with high accuracy and supplied to the comparator CMP2 as a voltage Va, and a voltage Vb corresponding to the reference current IREF can be generated. As a result, the number of components externally attached to the semiconductor integrated circuit 102 can be reduced, and the cost of a system including the semiconductor integrated circuit 102 can be reduced. Furthermore, since the number of components can be reduced, the reliability of the system including the semiconductor integrated circuit 102 can be improved.

[0063] Furthermore, the transistor PM22 of the regulator 40 that supplies the output voltage VOUT to the current load circuit 200 can be used to determine the magnitude of the power supply current supplied to the current load circuit 200. This allows the circuit scale of the current detection circuit 30 to be reduced.

[0064] When it is determined that the power supply current is insufficient, the functions of at least some of the circuits in the current load circuit 200 are stopped, thereby reducing the power consumption of the current load circuit 200. As a result, even when the supply of power supply current from the regulator 40 is insufficient, the minimum necessary circuits can be operated.

[0065] The transistors NM13 and NM14 shown in FIG. 1 are formed at positions adjacent to each other on a semiconductor substrate, so that the size ratio of the transistors NM13 and NM14 can be kept constant even if the semiconductor manufacturing process varies. In addition, the electrical characteristics of the transistors NM13 and NM14 can be changed in a similar manner in response to temperature changes in the semiconductor substrate. This allows the current ratio of the transistors NM13 and NM14 to be set with high precision. In addition, the resistor elements R13 and R14, which are set to the same resistance value, are formed at positions adjacent to each other on the semiconductor substrate, so that the resistance values ​​of the resistor elements R13 and R14 can be kept the same even if the semiconductor manufacturing process varies.

[0066] Although the present invention has been described above based on the embodiments, the present invention is not limited to the requirements shown in the above embodiments. These requirements can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of symbols]

[0067] 10 Current drive circuit 12 Reference voltage generation circuit 20, 30 Current detection circuit 40 Regulator 42 Reference voltage generation circuit 100, 102 Semiconductor integrated circuit 110 Transmitting circuit 120 Control section 200 current load circuit ACTH, ACTL active signal AMP1, AMP2 Amplifiers AOUT1, AOUT2 control signals BUF Buffer CMP comparison result signal CMP1, CMP2 comparators CS1, CS2 current source DATA DIV1, DIV2 divided voltage IREF Reference current IV11, IV12 inverter NM11, NM12, NM13, NM14 n-channel transistors PM21, PM22 p-channel transistors R11, R12, R13, R14, R15 Resistor elements R21, R22, R23, R24 Resistor elements SIO Serial input / output terminal Va, Vb voltage VIN Input voltage line VOUT Output voltage line VREF Reference voltage

Claims

1. A semiconductor integrated circuit having a first transistor connected to an input / output terminal connectable to a power supply terminal that supplies a voltage to a voltage line, the first transistor drawing a current from the voltage line in response to a control signal received at its gate, the current drive circuit being capable of outputting data as a change in voltage on the voltage line when the power supply terminal is connected to the input / output terminal, and a current detection circuit detecting a current supplied to the voltage line, The current detection circuit includes: a first resistor element and a second resistor element each having one end connected to the voltage line between the power supply terminal and the current driver circuit and having the same resistance value; a second transistor connected to the other end of the first resistance element, the second transistor having a transistor size that is 1 / N of the size of the first transistor, and the second transistor receiving the control signal at its gate; a current source connected to the other end of the second resistor element and configured to supply a reference current that is 1 / N of a desired current supplied to the voltage line; a comparator that determines whether or not the desired current is being supplied to the voltage line by comparing a voltage at the other end of the first resistor element, which is received at a first input, with a voltage at the other end of the second resistor element, which is received at a second input; A semiconductor integrated circuit comprising:

2. The current driver circuit includes a voltage divider circuit that divides the voltage of the voltage line to generate a divided voltage; a reference voltage generating circuit that generates a reference voltage having the same value as a divided voltage generated by the voltage dividing circuit when the voltage line has a voltage corresponding to the data having a low level; an amplifier that differentially amplifies the divided voltage and the reference voltage and generates the control signal to be supplied to the gate of the first transistor.

2. The semiconductor integrated circuit according to claim 1 .

3. The present invention further comprises an operation control circuit that stops the operation of the current detection circuit and the current source when the power supply terminal is connected to the input / output terminal and the data of a low level value is not output to the voltage line.

3. The semiconductor integrated circuit according to claim 2 .

4. a control unit that operates on a power supply voltage that is generated based on the voltage supplied from the voltage line; the comparator outputs a comparison result signal indicating whether the current drawn by the first transistor is smaller than the reference current to the control unit; The control unit stops a function of at least a part of a circuit of the control unit when the comparison result signal indicates that the current drawn by the first transistor is smaller than the reference current.

4. The semiconductor integrated circuit according to claim 1, wherein:

5. The current drive circuit is capable of outputting data as a change in voltage of the voltage line when the power supply terminal is connected to the input / output terminal via a resistive element.

4. The semiconductor integrated circuit according to claim 1, wherein:

6. A semiconductor integrated circuit comprising: a regulator having a first transistor having a source connected to a voltage line receiving an input voltage and a drain connected to an output terminal for outputting an output voltage, the first transistor outputting the output voltage to the output terminal in response to a control signal received at a gate thereof; and a current detection circuit detecting a current supplied to the voltage line, The current detection circuit includes: a first resistor element and a second resistor element each having one end connected to a low voltage line set to a voltage lower than the input voltage and having the same resistance value; a second transistor connected between the voltage line and the other end of the first resistor element, the second transistor having a transistor size that is 1 / N of the size of the first transistor, and the second transistor receiving the control signal at its gate; a current source connected between the voltage line and the other end of the second resistor element, the current source supplying a reference current that is 1 / N of a desired current supplied to the voltage line; a comparator that determines whether or not the desired current is being supplied to the voltage line by comparing a voltage at the other end of the first resistor element, which is received at a first input, with a voltage at the other end of the second resistor element, which is received at a second input; A semiconductor integrated circuit comprising:

Images