JP4620708B2 - Noise countermeasure determination device - Google Patents

Description

  The present invention relates to a technique applied when designing an electronic circuit such as an LSI (Large Scale Integration), an MCM (Multi Chip Module), a printed circuit board (PCB), and the like. The present invention relates to a noise countermeasure determining apparatus that determines a noise countermeasure method so that noise that can be generated in a circuit is minimized and an electronic circuit to be designed operates normally.

(Conventional technology)
A conventional example will be described below. With recent miniaturization and speedup of various electronic devices (for example, LSI, MCM, PCB, etc.), noise analysis and noise countermeasures have become important. For this reason, various noise analysis tools are provided. In these noise analysis tools, noise analysis and noise check are performed using a circuit simulator after the mounting design is completed, and noise countermeasures are determined.

  After that, the design was changed based on the determined noise countermeasure, and after the design change, the noise analysis and the noise check were performed again, and the above operation was repeated until the noise problem disappeared.

  The main noises to be considered when designing an electronic circuit include reflection noise and crosstalk noise. Usually, the reflected noise is generated due to mismatch between the internal resistance of the driver and the characteristic impedance of the transmission line. In order to suppress this reflected noise, particularly in the case of one-to-one transmission, a method of inserting a damping resistor in series with the output of the driver is known, and the sum of the internal resistance value of the driver and the damping resistance value is A method of selecting a damping resistance value that has the same relationship as the characteristic impedance of the transmission line is employed.

  Reflection noise other than one-to-one transmission (one-to-N transmission) greatly depends on the wiring topology. At present, the selection of the wiring topology is performed manually, and the designer performs wiring suitable for the selected wiring topology. A circuit simulator is executed based on the wiring information, and noise analysis and noise check are performed. If there is a noise problem as a result of the analysis, a method is adopted in which the wiring topology is changed, re-wiring according to the wiring topology, noise analysis, noise check is repeated, and the optimum wiring topology is found.

  The conventional apparatus as described above has the following problems.

  That is, with the recent miniaturization and speeding up of various electronic devices, the number of nets that require noise analysis and noise countermeasures has increased, and the design man-hours have increased. For this reason, it has become necessary to take countermeasures against noise such that circuit design, mounting design, and noise analysis are not repeated. Therefore, it is necessary to create a circuit model for at least one net before circuit design and mounting design, and input the circuit model to determine noise countermeasures.

  In addition, even when a circuit model for at least one net is created before circuit design and mounting design, and noise analysis and noise countermeasures are performed, a circuit simulator is always executed, and noise countermeasures are determined based on the results of the circuit simulator. However, since the processing time of the circuit simulator is longer than that of other processes, there is a problem that the entire processing time increases. In particular, the problem becomes large when a work cycle such as design, analysis, countermeasure (design change), and analysis is repeated. Therefore, a mechanism for determining noise countermeasures while minimizing the execution of the circuit simulator is required.

  Furthermore, in order to minimize the execution of the circuit simulator, it is necessary to determine the damping resistance without using the result of the circuit simulator in the reflection noise countermeasure. If the recommended circuit information is the damping resistance value that matches the characteristic impedance of the wiring and the output resistance of the driver element, the damping resistance value already inserted in the input circuit information does not match even if there is no problem with the actual transmission waveform Therefore, it may be determined that the damping resistance value needs to be changed as a noise countermeasure. For this reason, a mechanism for determining noise countermeasures using a damping resistance value in a range where no problem occurs in circuit operation as recommended circuit information is necessary.

  In determining the wiring topology, it is necessary to repeat the selection of the wiring topology, the wiring change, and the noise analysis, but there is a problem that it takes time if the designer has selected the wiring topology and the wiring change. Therefore, there is a need for a mechanism that repeats wiring topology and wiring change and noise analysis in a short time, selects an optimal wiring topology, and determines noise countermeasures.

  The present invention solves such a conventional problem and aims at the following. A first object of the present invention is to determine noise countermeasures before performing circuit design and mounting design, so that the noise countermeasures can be determined at high speed without reversing the design process.

  A second object of the present invention is to make it possible to determine a damping resistance value in a range that is not excessively limited without requiring execution of a circuit simulator. A third object of the present invention is to make it possible to determine an optimum wiring topology from an assumed positional relationship on an actual board before performing circuit design and mounting design.

  FIG. 1 is a diagram for explaining the principle of the present invention. In FIG. 1, 1 is a circuit information storage unit that stores circuit information, 2 is a noise countermeasure determination processing unit that performs noise countermeasure determination processing, and 3 is a noise countermeasure determination processing unit 2. The noise countermeasure information storage unit 4 stores the noise countermeasure information determined by 1 is a database storing circuit constant relation tables. In order to achieve the above object, the present invention is configured as follows.

(1): It is provided with a circuit information storage unit 1 that stores circuit information that has been created in advance and a database 4 that stores a circuit constant relationship table that defines the relationship between circuit constants. By inputting circuit information (circuit information storage unit 1 information) of the circuit and referring to the information in the database, it is possible to suppress noise within a range in which the electronic circuit operates normally in the one-to-one transmission circuit. A noise countermeasure determining apparatus that determines a noise countermeasure method, wherein the circuit information includes a driver internal resistance value, a driver saturation current value, and a driver power supply voltage value, and from these input information, the driver power supply By subtracting the internal resistance value of the driver from the value obtained by dividing the voltage value by the saturation current value of the driver, the minimum value of the characteristic impedance of the transmission line is set at the receiver. Wherein the sub-circuit is provided with a noise countermeasure determining means (noise countermeasure determining unit 2) for determining a noise suppression method the minimum value of the characteristic impedance of the transmission line as a voltage to operate properly.

(2): A circuit information storage unit 1 for storing previously created circuit information (information of the circuit information storage unit 1) and a database 4 storing a circuit constant relationship table that defines the relationship between circuit constants are provided. A noise countermeasure determining apparatus that inputs circuit information of a target circuit from the circuit information storage unit 1 and determines a noise countermeasure method for suppressing noise within a range in which an electronic circuit normally operates in a one-to-two transmission circuit. Then, as the circuit information, using the equivalent capacitance value of the receiver of one transmission line , the equivalent capacitance value of the receiver of the other transmission line, and the characteristic impedance value of the one transmission circuit, from these input information A value obtained by dividing the product of the equivalent capacitance value of the receiver of the one transmission line and the characteristic impedance value of the one by the equivalent capacitance value of the receiver of the other transmission line is the value of the other transmission circuit. By determining the characteristic impedance value, the electronic circuit includes a noise countermeasure determining means (noise countermeasure determining unit 2) for determining a characteristic impedance value of the load balance and becomes like the other transmission circuit operates normally It is characterized by.

(Function)
The operation of the present invention based on the above configuration will be described below.

  The operation of the present invention based on the above configuration will be described.

  (a): In (1) above, the noise countermeasure determining means uses the internal resistance value of the driver, the saturation current value of the driver, and the power supply voltage value of the driver as circuit information. The minimum value of the characteristic impedance of the transmission line that is a voltage at which the electronic circuit operates normally is determined as a noise countermeasure method.

  In this way, since the characteristic impedance value of the transmission line that prevents the electronic circuit from operating normally can be found without repeating the circuit simulation, the number of design steps can be reduced as compared with the conventional case.

(b): In the above (2), the noise countermeasure deciding means uses, as circuit information, the equivalent capacitance value of the receiver of one transmission line, the equivalent capacitance value of the receiver of the other transmission line, and the one of the transmission circuits. Using the characteristic impedance value, from this input information, the product of the equivalent capacitance value of one transmission line receiver and the characteristic impedance value of one transmission line divided by the equivalent capacitance value of the other transmission line receiver, Obtained as the characteristic impedance value of the transmission circuit.

In this way, since the characteristic impedance value of the branched transmission line that allows the electronic circuit to operate normally can be determined without repeating the circuit simulation, the number of design steps can be reduced as compared with the conventional case.

  The present invention has the following effects according to claims 1 and 2.

  (a): In claim 1, the noise countermeasure determining means uses the internal resistance value of the driver, the saturation current value of the driver, and the power supply voltage value of the driver as circuit information. The minimum value of the characteristic impedance of the transmission line that is a voltage at which the circuit operates normally is determined as a noise countermeasure method.

  In this way, since the characteristic impedance value of the transmission line that prevents the electronic circuit from operating normally can be found without repeating the circuit simulation, the number of design steps can be reduced as compared with the conventional case.

  (b): In claim 2, the noise countermeasure determining means uses the equivalent capacitance value of the two receivers and the characteristic impedance value of one of the transmission lines as circuit information. The characteristic impedance value of the other transmission line that determines the load balance to operate is determined.

  In this way, since the characteristic impedance value of the branched transmission line that allows the electronic circuit to operate normally can be determined without repeating the circuit simulation, the number of design steps can be reduced as compared with the conventional case.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

§1: Description of noise countermeasure determining device and data, etc. Hereinafter, the noise countermeasure determining device, data, and the like will be described with reference to FIGS.

(1): Explanation of noise countermeasure determination device
(a): Explanation of Configuration of Noise Countermeasure Determination Device FIG. 2 is a block diagram of the noise countermeasure determination device, FIG. A is a basic device configuration diagram, and FIG. B is a specific device example. The noise countermeasure determining apparatus includes a circuit information storage unit 1, a database 4, a noise countermeasure determination processing unit 2, and a noise countermeasure information storage unit 3. The circuit information storage unit 1 stores information on a circuit created by another device in advance (generally, information on a circuit such as an LSI created by a user) (for example, a magnetic disk device). .

  The database 4 stores a circuit constant relationship table that defines the relationship between circuit constants. The database 4 is created by the manufacturer of the noise countermeasure determining apparatus and provided to the user, and the user cannot rewrite the data (the user only reads and uses the data in the database 4). The noise countermeasure determination processing unit 2 performs the noise countermeasure determination process by inputting the information in the circuit information storage unit 1 and referring to the information in the database 4, and is realized by executing a program. The noise countermeasure information storage unit 3 stores information determined by the noise countermeasure determination processing unit 2 (for example, a magnetic disk device). When the noise countermeasure determination processing unit 2 performs the noise countermeasure determination processing, the circuit information storage unit 1 and the data in the database 4 are stored in advance in the magnetic disk device.

(b): Description of Specific Device Example and Recording Medium A specific device example of the noise countermeasure determining device is shown in FIG. 2B. The noise countermeasure determining apparatus can be realized by the apparatus shown in FIG. 2B, for example. This apparatus example is an apparatus realized by an arbitrary computer such as a personal computer or a workstation, and includes a computer main body 11, a display device 12 connected to the computer main body 11, an input device 13 such as a keyboard and a mouse, and a removable disk. A drive (RDD) 14, a magnetic disk device (MDD) 15, a printer 16, and the like are provided.

  The computer main body 11 includes a CPU (central processing unit) 17 for performing various controls in the apparatus, a ROM (nonvolatile memory) 18 for storing data such as programs and various parameters, and a CPU 17. A memory 19 used as an interface, an interface control unit (I / F control unit) 20 that performs interface control with an external I / O device, a communication control unit 21 that performs communication control with the outside, and the like are provided.

  The noise countermeasure determining process performed by the noise countermeasure determining apparatus is executed by the CPU 17 reading and executing a program stored (recorded or stored) in the magnetic disk of the magnetic disk device (MDD) 15 or the ROM 18 in advance. To do. However, the present invention is not limited to such an example. For example, the program is stored in the magnetic disk (recording medium) of the magnetic disk device 15 as follows, and the CPU 17 executes the program to execute the program. It is also possible to perform processing.

  a: A program stored on a removable disk (floppy disk, CD-ROM, other optical disk, etc.) created by another device (a program created by another device) is read by the removable disk drive 14, and a magnetic disk It is stored in a recording medium (magnetic disk) of the device 15.

  b: Data such as a program transmitted from another device via various communication lines such as LAN and the Internet is received via the communication control unit 21, and the data is recorded on the recording medium (magnetic disk) of the magnetic disk device 15. To store.

(2): Explanation of Terms FIG. 3 is an explanatory diagram of a circuit configuration, A is an explanatory diagram of a driver / receiver, B is an explanatory diagram of one-to-one transmission, and C is an explanatory diagram of one-to-two transmission. is there. 4 is an explanatory diagram of a correspondence table, FIG. 4A is an explanatory diagram of a correspondence table of voltage and current at the time of pull-up, and FIG. 4B is an explanatory diagram of a correspondence table of voltage and current at the time of pull-down. FIG. 5 is an example of a correspondence table, FIG. 5A is an example of a correspondence table of voltage and current at the time of pull-up, FIG. 5B is an example of correspondence table of voltage and current at the time of pull-down, FIG. It is Table example 2. Hereinafter, the terms used in the following description and the contents thereof will be described with reference to FIGS.

(a): "Driver", "Receiver"
As shown in FIG. 3A, for example, when a signal is transmitted from the LSI 1 to the LSI 2 on the transmission line on the electronic circuit, an output circuit that drives the transmission signal of the LSI 1 is referred to as a “driver”. An input circuit for receiving a transmission signal of the LSI 2 is called a “receiver”.

(b): "Pull-up"
As shown in FIG. 4A, connecting the power supply voltage value as the internal input of the driver is called “pull-up”.

(c): "Pull-down"
As shown in FIG. 4B, connecting to the ground (0V) as an internal input of the driver is called “pull-down”.

(d): “Voltage and current correspondence table at driver pull-up”
In the voltage source B connected to the external output A of the driver shown in FIG. 4A, the correspondence between the current value between the external output A of the driver and the voltage source B and the voltage value (voltage value of the voltage source B) is tabulated. This is called a “voltage / current correspondence table at the time of driver pull-up”. As an example, there is a table as shown in FIG.

(e): “Voltage and current correspondence table during driver pull-down”
In the voltage source B connected to the external output A of the driver shown in FIG. 4B, the correspondence between the current value and the voltage value (voltage value of the voltage source B) between the external output A and the voltage source B is tabulated. Is called a “voltage-current correspondence table when the driver is pulled down”. As an example, there is a table as shown in FIG.

(f): “One-to-one transmission”
On the electronic circuit, for example, transmission when the driver and the receiver are connected one-to-one as shown in FIG. 3B is called “one-to-one transmission”.

(g): "1 to 2 transmission"
On the electronic circuit, for example, transmission when the driver and the receiver are connected in a one-to-two manner as shown in FIG. 3C is referred to as “one-to-two transmission”.

(h): “Driver rise time”
The time taken for the output voltage of the driver to rise from zero volts to the power supply voltage value is called “driver rise time”.

(i): “Driver fall time”
The time required for the output voltage of the driver to drop from the power supply voltage value to zero volts is referred to as “driver fall time”.

(3): Description of circuit information and database Example of correspondence table of voltage and current at the time of driver pull-up shown in FIG. 5A, and voltage and current at the time of driver pull-down shown in FIG. The correspondence table example is an example of information stored in the circuit information storage unit 1 and is input by the user.

  In the correspondence table of voltage and current at the time of pull-up of the driver shown in FIG. 5A, “voltage value” = voltage value of the voltage source B, “current value” = between the external output A of the driver and the voltage source B Indicates the current value of the current flowing through the transmission line. According to this driver pull-up voltage-current correspondence table, for example, when the voltage value = 0V, the current value = −60 mA, the voltage value = 3.12 V, the current value = −10 mA, and the voltage value = At 3.3 V, the current value is 0 mA.

  Further, in the correspondence table of the voltage and current at the time of pull-down of the driver shown in FIG. 5B, “voltage value” = voltage value of the voltage source B, “current value” = between the external output A of the driver and the voltage source B The current value of the current flowing through the transmission line is shown. According to the voltage-current correspondence table when the driver is pulled down, when the voltage value = −0.2V, the current value = −10 mA, when the voltage value = 0V, the current value = 0 mA, and the voltage value = 3.3V. In this case, the current value is 55 mA.

  The relationship table example 1 shown in FIG. 5C and the relationship table example 2 shown in FIG. 5D are stored in the database 4 and are provided by the manufacturer.

  In the relationship table example 1 shown in FIG. 5C, data is stored for each item of the internal resistance value, the characteristic impedance value of the transmission line, the voltage value of the receiver, and the damping resistance value. For example, in the relationship table example 1, the internal resistance value = 20Ω, the transmission line characteristic impedance value = 60Ω, the receiver voltage value = 0.6V, and the damping resistance value = 16Ω correspond to each other. In addition, data of internal resistance value = 20Ω, characteristic impedance value of transmission line = 60Ω, voltage value of receiver = 1.2V, and damping resistance value = 118Ω correspond to each other.

  In the relationship table example 2 shown in FIG. 5D, data is obtained for each item of the rise (fall) time, the propagation delay time per unit length of the transmission line, and the shortest insertion position from the driver of the damping resistor. Stored. According to this example table, the rise (fall) time = 2.0, the propagation delay time per unit length of the transmission line = 0.6, and the shortest insertion position from the driver of the damping resistor = 1.67. ing.

(4): Explanation of processing outline The outline of the processing performed by the noise countermeasure determination processing section 2 is as follows.

  (a): The circuit information of the target circuit (information in the circuit information storage unit 1) is input, and the electronic circuit is normal in the one-to-one transmission circuit by referring to the information in the database 4 that defines the circuit constants. In the process of determining a noise countermeasure method for suppressing noise within a range that operates normally, as the circuit information, the allowable voltage range of the receiver in which the electronic circuit operates normally, the power supply voltage value of the driver, and the characteristics of the transmission line Using the impedance value and the internal resistance value of the driver, the range of the damping resistance value in which the electronic circuit operates normally is determined from the input information as a noise countermeasure method.

  (b): The circuit information of the target circuit (information in the circuit information storage unit 1) is input, and the electronic circuit is normal in the one-to-one transmission circuit by referring to the information in the database 4 that defines the circuit constants. In the process of determining a noise countermeasure method for suppressing noise within the operating range, the rise time of the driver, the fall time of the driver, and the propagation delay time per unit length of the transmission line are used as the circuit information. From these input information, the shortest insertion position from the driver of the damping resistor that suppresses the reflection noise and operates the electronic circuit normally is determined as a noise countermeasure method.

  (c): Inputs circuit information of the target circuit (information of the circuit information storage unit 1), and determines a noise countermeasure method for suppressing the noise within a range where the electronic circuit operates normally in the one-to-one transmission circuit. In this process, as the circuit information, the internal resistance value of the driver, the saturation current value of the driver, and the power supply voltage value of the driver are used, and from this input information, the voltage at which the electronic circuit operates normally in the receiver is transmitted. The minimum value of the characteristic impedance of the line is determined as a noise countermeasure method.

  (d): In the noise countermeasure determination processing, the current value 0 amperes in the pull-up voltage / current correspondence table is used as the internal resistance value at the pull-up from the driver voltage / current correspondence table given as circuit information. Based on the first processing for obtaining the internal resistance value in the vicinity and the voltage / current correspondence table of the driver, as the internal resistance value at the time of pull-down, the current value near 0 amperes in the voltage / current correspondence table at the time of pull-down A second process for obtaining the internal resistance value and a third process for obtaining the larger one of the two obtained internal resistance values as the internal resistance value of the driver are performed.

  (e): In the noise countermeasure determination processing, as circuit information, information on the correspondence table between the voltage and current at the time of pulling down the driver, information on the correspondence table between the voltage and current at the time of pulling up the driver and the power supply voltage value of the driver Is used to obtain a current value corresponding to a voltage value equal to the power supply voltage value of the driver from a correspondence table of the voltage and current at the time of pulling down the driver, and determine a saturation current value at the time of pulling down. A second saturation current determination process for determining a current value corresponding to a voltage value of 0 volts from a correspondence table of the voltage and current at the time of pull-up of the driver and determining a saturation current value at the time of pull-up; Of the saturation current values determined in the first and second saturation current determination processes, a smaller value is determined as the saturation current value of the driver. Do the reason.

  (f): Inputs circuit information of the target circuit (information in the circuit information storage unit 1), and determines a noise countermeasure method for suppressing the noise within a range where the electronic circuit operates normally in the one-to-two transmission circuit. The noise countermeasure determination processing is to use the equivalent capacitance value of two receivers and the characteristic impedance value of one transmission line as the circuit information. From these input information, the load balance at which the electronic circuit operates normally and The characteristic impedance value of the other transmission line is determined.

§2: Detailed description of processing Hereinafter, the processing of the noise countermeasure determining apparatus will be described in detail for each example.

(1): Example 1
FIG. 6 is a processing flowchart of Example 1. Hereinafter, the processing of Example 1 will be described with reference to FIG. In addition, S1-S4 shows each process step.

  In Example 1, circuit information in the circuit information storage unit 1 (receiver input voltage allowable maximum value, driver power supply voltage value, receiver input voltage allowable minimum value, transmission line characteristic impedance value, driver internal resistance value) Is input data, the circuit constant relation table in the database 4 is referred (searched), and the noise countermeasure determination processing unit 2 performs the noise countermeasure determination process, and the range of the damping resistance value (minimum and maximum values of the damping resistance value) Is stored in the noise countermeasure information storage unit 3. In Example 1, the process is performed when the internal resistance value of the driver has already been obtained and is provided as circuit information.

  First, the noise countermeasure determination processing unit 2 sets a value obtained by dividing the allowable maximum value of the input voltage of the receiver by the power supply voltage value of the driver as a normalized allowable maximum value of the input voltage of the receiver (S1). Next, using the value, the characteristic impedance of the transmission line, and the internal resistance value of the driver as a key, the relation table of the database 4 is referred (searched) to obtain the minimum value of the damping resistance value (S2).

  At the same time, the noise countermeasure determination processing unit 2 sets a value obtained by dividing the allowable minimum value of the input voltage of the receiver by the power supply voltage value of the driver as a normalized allowable minimum value of the input voltage of the receiver (S3). Thereafter, using the value, the characteristic impedance of the transmission line, and the internal resistance value of the driver as keys, the relationship table is referenced (searched) to obtain the maximum value of the damping resistance value (S4). The range of the minimum value and the maximum value of the damping resistance value acquired in this way is set as the range of the damping resistance value.

(2): Example 2
FIG. 7 is a processing flowchart of Example 2. Hereinafter, the processing of Example 2 will be described with reference to FIG. S11 and S12 indicate each processing step.

  In Example 2, circuit information (driver rise time, driver fall time, propagation delay time per unit length of transmission line) is input in the circuit information storage unit 1, and the circuit constant relation table in the database 4 is referenced ( The noise countermeasure determination processing unit 2 performs a noise countermeasure determination process by searching, and obtains the shortest insertion position of the damping resistance value from the driver and stores it in the noise countermeasure information storage unit 3.

  First, the noise countermeasure determination processing unit 2 acquires the smaller value of the driver rise time and driver fall time (S11). Next, using the value and the propagation delay time per unit length of the transmission line as a key, the circuit constant relationship table in the database 4 is referred (searched) to obtain the shortest insertion position from the driver of the damping resistor (S12). ).

(3): Example 3
FIG. 8 is a processing flowchart of Example 3. Hereinafter, the process of Example 3 will be described with reference to FIG. S15 indicates a processing step.

  In Example 3, the noise countermeasure determination processing unit 2 performs processing using circuit information (driver internal resistance value, driver saturation current value, driver power supply voltage value) in the circuit information storage unit 1 as input data, and the transmission line The minimum value of the characteristic impedance is obtained and stored in the noise countermeasure information storage unit 3. In Example 3, the internal resistance value of the driver and the saturation current value of the driver have already been obtained and are provided when provided as circuit information.

  First, the noise countermeasure determination processing unit 2 sets the value obtained by subtracting the internal resistance value of the driver from the value obtained by dividing the power supply voltage value of the driver by the saturation current value of the driver as the minimum value of the characteristic impedance of the transmission line ( S15).

(4): Example 4
FIG. 9 is a processing flowchart (part 1) of Example 4, and FIG. 10 is a processing flowchart (part 2) of Example 4. FIG. 9 is a flowchart of the entire process of Example 4. FIG. 10 is a detailed process of S21 and S22 of FIG. 9 (a process of obtaining an internal resistance value near a current value of 0 A), and S21 to S26. Indicates processing steps. Hereinafter, the process of Example 4 will be described with reference to FIGS. 9 and 10.

(a): Overall processing As shown in FIG. 9, in Example 4, the circuit information in the circuit information storage unit 1 (corresponding table of voltage and current at the time of driver pull-up, voltage and current at the time of driver pull-down) The noise countermeasure determination processing unit 2 performs processing using the correspondence table) as input data, and calculates the internal resistance value of the driver and stores it in the noise countermeasure information storage unit 3. Example 4 is a process for obtaining the internal resistance value of the driver when the internal resistance value of the driver is unknown (when not obtained) when performing the processes of Examples 1 and 3.

  First, the noise countermeasure determination processing unit 2 obtains an internal resistance value when the current value is near 0 A from the voltage-current correspondence table at the time of pull-up of the driver (S21), and uses this value as the internal resistance at the time of pull-up. Value. Further, an internal resistance value in the vicinity of the current value of 0 A is obtained from the voltage-current correspondence table at the time of pulling down the driver (S22), and this value is set as the internal resistance value at the time of pulling down. Then, the larger one of the internal resistance value at the time of pull-up and the internal resistance value at the time of pull-down is obtained as the internal resistance value of the driver (S23).

(b): Detailed processing of S21 and S22 (processing for obtaining an internal resistance value near a current value of 0 A)
In this process, the noise countermeasure determination processing unit 2 determines, from the voltage-current correspondence table (pull-up and pull-down correspondence table), the current value “A1” that is the smallest among the current values of 0 A or more, The corresponding voltage value “V1” is acquired (S24). Further, the noise countermeasure determination processing unit 2 obtains the maximum current value “A2” and the corresponding voltage value “V2” among the current values less than 0 A from the voltage and current correspondence table (S25). .

  Next, the noise countermeasure determination processing unit 2 obtains a value obtained by dividing the difference between “V1” and “V2” by the difference between “A1” and “A2” as an internal resistance value (S26). In the above-described processing, the processing for obtaining the internal resistance value at the time of pull-up and the processing for obtaining the internal resistance value at the time of pull-down are described (commonly).

(5): Example 5
FIG. 11 is a processing flowchart of Example 5. Hereinafter, the processing of Example 5 will be described with reference to FIG. S31 to S33 indicate processing steps.

  In example 5, the circuit information (driver pull-down voltage and current correspondence table, driver pull-up voltage and current correspondence table, driver power supply voltage value) in the circuit information storage unit 1 is used as input data for noise suppression. The determination processing unit 2 performs processing, obtains a saturation current value of the driver, and stores it in the noise countermeasure information storage unit 3. In Example 5, when the processing of Example 3 is performed, the saturation current value of the driver is obtained when the saturation current value of the driver is unknown.

  The noise countermeasure determination processing unit 2 first obtains a current value equal to the power supply voltage value of the driver from the correspondence table of the voltage and current at the time of pulling down the driver, and sets this value as the saturation current value at the time of pulling down (S31). Further, the noise countermeasure determination processing unit 2 obtains a current value corresponding to a voltage value of 0 V from the voltage-current correspondence table at the time of pull-up of the driver, and uses this value as a saturation current value at the time of pull-up (S32). ).

  Then, the noise countermeasure determination processing unit 2 obtains the smaller one of the saturation current value at the time of pull-down and the saturation current value at the time of pull-up, and uses this value as the saturation current value of the driver (S33).

(6): Example 6
FIG. 12 is a processing flowchart of Example 6, A is a one-to-two transmission explanatory diagram, and B is a processing flowchart. Hereinafter, the process of Example 6 will be described with reference to FIG. S35 indicates a processing step.

  Example 6 is processing for determining the characteristic impedance value of the transmission line 2 when the characteristic impedance value of the transmission line 1 is determined in the one-to-two transmission as shown in FIG.

  In the processing of Example 6, the noise countermeasure determination processing unit 2 performs processing using circuit information (equivalent capacity of the receiver A, equivalent capacity of the receiver B, characteristic impedance value of the transmission line 1) in the circuit information storage unit 1 as input data. Then, the characteristic impedance value of the transmission line 2 is obtained and stored in the noise countermeasure information storage unit 3.

  The noise countermeasure determination processing unit 2 obtains a value obtained by dividing the product of the equivalent capacitance of the receiver A and the characteristic impedance value of the transmission line 1 by the equivalent capacitance of the receiver B, and uses this value as the characteristic impedance value of the transmission line 2. (S35).

§3: Description with specific numerical examples Hereinafter, the above-described Examples 1 to 6 will be described with specific numerical examples. As specific numerical values, examples of correspondence table of voltage and current at the time of pull-up shown in FIG. 5A, example of correspondence table of voltage and current at the time of pull-down shown in FIG. The relationship table example 1 shown in FIG. 5C and the relationship table example 2 shown in FIG. 5D are used.

(1): Process of Example 1 In the process of Example 1, the process is performed as follows. In this case, it is assumed that one-to-one transmission exists in a certain electronic circuit. Then, the power supply voltage value of the driver = 3.3V, the internal resistance value of the driver = 20Ω, the range of the voltage value of the receiver that recognizes the signal as high level = 2.0V to 4.1V, the transmission line between the driver and the receiver It is assumed that the characteristic impedance value is 60Ω.

  The noise countermeasure determination processing unit 2 inputs the information as circuit information and performs processing. In this process, normalized minimum allowable input voltage = 2.0 / 3.3 = 0.006V. Also, normalized maximum allowable value of input voltage = 4.1 / 3.3 = 1.2424V.

  Therefore, when the noise countermeasure determination processing unit 2 refers to the relation table of the database 4 using these pieces of information as keys, the range of the damping resistance value = 16Ω to 118Ω. The range of the damping resistance value is stored in the noise countermeasure information storage unit 3 as a noise countermeasure method.

(2): Processing of Example 2 In the processing of Example 2, the processing is performed as follows. In this case, it is assumed that one-to-one transmission exists in a certain electronic circuit. The rise time of the driver is set to 2.0 nanoseconds, and the propagation delay time per millimeter of the transmission line between the driver and the receiver is set to 0.6 nanoseconds.

  The noise countermeasure determination processing unit 2 inputs the information as circuit information and performs processing. In this process, since the smaller value of the rise time and the fall time is 2.0 nanoseconds, by referring to the relation table of the database 4 using these information as a key, the shortest insertion from the driver of the damping resistor is performed. Position = 1.67 mm. The noise countermeasure determination processing unit 2 stores the shortest insertion position of the damping resistor from the driver in the noise countermeasure information storage unit 3 as a noise countermeasure method.

(3): Process of Example 3 In the process of Example 3, the process is performed as follows. In this case, it is assumed that one-to-one transmission exists in a certain electronic circuit. Then, the power supply voltage of the driver is 3.3 V, the internal resistance value of the driver is 20Ω, and the saturation current value of the driver is 5.5 mA.

  The noise countermeasure determination processing unit 2 inputs the information as circuit information and performs processing. In this process, the minimum characteristic impedance of the transmission line = (3.3 V / 55 mA) −20Ω = 40Ω. The noise countermeasure determination processing unit 2 stores the minimum value of characteristic impedance of the transmission line = 40Ω in the noise countermeasure information storage unit 3 as a noise countermeasure method.

(4): Process of Example 4 In the process of Example 4, the process is performed as follows. In this case, it is assumed that one-to-one transmission exists in a certain electronic circuit. Then, the noise countermeasure determination processing unit 2 obtains an internal resistance value at the time of pull-up from a correspondence table of voltage and current at the time of pull-up of the driver. In this case, according to the voltage-current correspondence table when the driver is pulled up, the voltage value when the current is 0 A = 3.3V, and the voltage value when the current = −10 mA = 3.12V.

  Therefore, when the difference between 3.3V and 3.12V is divided by 10 mA, the internal resistance value at the time of pull-up becomes 18Ω. Similarly, according to the voltage / current correspondence table when the driver is pulled down, the voltage value when the current = 0A = 0V, and the voltage value when the current is −10 mA = −0.2V. In this case, when the difference between 0 V and −0.2 V is divided by 10 mA, the internal resistance value at the time of pull-down is 20Ω.

  Therefore, the larger one of the internal resistance value at pull-up = 18Ω and the internal resistance value at pull-down = 20Ω = 20Ω, and the internal resistance value of the driver = 20Ω. The internal resistance value of this driver = 20Ω is used as data in Examples 1 and 3.

(5): Process of Example 5 In the process of Example 5, the process is performed as follows. In this case, it is assumed that one-to-one transmission exists in a certain electronic circuit. In this case, the power supply voltage value of the driver is 3.3V.

  The noise countermeasure determination processing unit 2 first obtains a current value corresponding to a voltage value equal to the power supply voltage value of the driver = 3.3 V from the correspondence table of the voltage and current at the time of pulling down the driver, and obtains this value at the time of pulling down. Saturation current value. In this example, according to the voltage-current correspondence table at the time of pull-up of the driver, the current value at the voltage value of 0 V = −60 mA, so the absolute value of 60 mA is used as the saturation current value at the time of pull-up. (= 60 mA).

  Similarly, the saturation current value at the time of pull-down is obtained from the correspondence table of voltage and current at the time of pull-down. In this example, according to the voltage / current correspondence table at the time of pull-down of the driver, the voltage value equal to the power supply voltage value of the driver = 3.3 V and the current value corresponding to 55 mA, so this value is left as it is and the saturation at the time of pull-down. The current value (= 55 mA) is used.

  Then, the noise countermeasure determination processing unit 2 obtains the smaller value = 55 mA of the saturation current value at the time of pull-down = 55 mA and the saturation current value at the time of pull-up = 60 mA, and this value = 55 mA is obtained as the saturation current of the driver. Value. The saturation current value = 55 mA of this driver is used as the data of Example 3.

(6): Process of Example 6 In the process of Example 6, the process is performed as follows. In this case, it is assumed that one-to-two transmission exists in a certain electronic circuit. Then, the noise countermeasure determination processing unit 2 sets the equivalent capacitance of the receiver A = 2 pF, the equivalent capacitance of the receiver B = 3 pF, and the characteristic impedance value of the transmission line 1 = 60Ω.

  The noise countermeasure determination processing unit 2 obtains a value = 40Ω obtained by dividing the product of the equivalent capacitance of the receiver A = 2 pF and the characteristic impedance value of the transmission line 1 = 60Ω by the equivalent capacitance of the receiver B = 3 pF, and this value = 40Ω Is the characteristic impedance value of the transmission line 2.

(Other explanation)
By the way, with the further miniaturization and speeding up of various electronic devices in recent years, the number of nets that require noise analysis and noise countermeasures has increased, and the design man-hours have increased. For this reason, it has become necessary to take countermeasures against noise such that circuit design, mounting design, and noise analysis are not repeated. In this case, it is necessary to create a circuit model for at least one net before circuit design and mounting design, and input the circuit model to determine noise countermeasures.

  In addition, even when a circuit model for at least one net is created before circuit design and mounting design, and noise analysis and noise countermeasures are performed, a circuit simulator is always executed, and noise countermeasures are determined based on the results of the circuit simulator. However, since the processing time of the circuit simulator is longer than that of other processes, there is a problem that the entire processing time increases. In particular, the problem becomes large when a work cycle such as design, countermeasure (design change), and analysis is repeated. Therefore, a mechanism for determining noise countermeasures while minimizing the execution of the circuit simulator is required.

  Furthermore, in order to minimize the execution of the circuit simulator, it is necessary to determine the damping resistance without using the result of the circuit simulator in the reflection noise countermeasure. If the recommended circuit information is the damping resistance value that matches the characteristic impedance of the wiring and the output resistance of the driver element, the damping resistance value already inserted in the input circuit information does not match even if there is no problem with the actual transmission waveform Therefore, it may be determined that the damping resistance value needs to be changed as a noise countermeasure. For this reason, a mechanism for determining noise countermeasures using a damping resistance value in a range where no problem occurs in circuit operation as recommended circuit information is necessary.

  In determining the wiring topology, it is necessary to repeat the selection of the wiring topology, the wiring change, and the noise analysis, but there is a problem that it takes time if the designer has selected the wiring topology and the wiring change. Therefore, there is a need for a mechanism that repeats wiring topology and wiring change and noise analysis in a short time, selects an optimal wiring topology, and determines noise countermeasures.

  The following configuration is appended to the above description.

(Appendix 1)
A noise countermeasure method for suppressing noise within a range in which an electronic circuit normally operates in a one-to-one transmission circuit by inputting circuit information of a target circuit and referring to information in a database defining circuit constants. A noise countermeasure determining device for determining,
As the circuit information, the electronic circuit operates normally, the allowable voltage range in the receiver, the power supply voltage value of the driver, the characteristic impedance value of the transmission line, and the internal resistance value of the driver, from these input information, A noise countermeasure determining device comprising noise countermeasure determining means for determining a range of a damping resistance value in which an electronic circuit operates normally while suppressing reflection noise, as a noise countermeasure method.

(Appendix 2)
A noise countermeasure method for suppressing noise within a range in which an electronic circuit normally operates in a one-to-one transmission circuit by inputting circuit information of a target circuit and referring to information in a database defining circuit constants. A noise countermeasure determining device for determining,
As the circuit information, the rise time of the driver, the fall time of the driver, and the propagation delay time per unit length of the transmission line are used, and from these input information, the reflection noise is suppressed and the electronic circuit operates normally. A noise countermeasure deciding device comprising noise countermeasure deciding means for deciding a shortest insertion position from a resistor driver as a noise countermeasure method.

(Appendix 3)
A noise countermeasure determining apparatus that inputs circuit information of a target circuit and determines a noise countermeasure method for suppressing noise within a range in which an electronic circuit normally operates in a one-to-one transmission circuit,
As the circuit information, the internal resistance value of the driver, the saturation current value of the driver, and the power supply voltage value of the driver are used. From these input information, the characteristic impedance of the transmission line that becomes the voltage at which the electronic circuit operates normally in the receiver A noise countermeasure determining device comprising noise countermeasure determining means for determining a minimum value as a noise countermeasure method.

(Appendix 4)
The internal resistance value in the vicinity of the current value of 0 amperes in the pull-up voltage-current correspondence table is obtained as the internal resistance value at the time of pull-up from the driver voltage-current correspondence table given as the circuit information. 1 internal resistance value determining means;
A second internal resistance value determining means for obtaining an internal resistance value near a current value of 0 amperes in the pull-down voltage-current correspondence table as a pull-down internal resistance value from the driver voltage-current correspondence table; ,
(Additional remark 1) or (Additional remark) characterized by comprising the 3rd internal resistance value determination means which calculates the larger internal resistance value as an internal resistance value of a driver among the calculated 2 internal resistance values 3) The noise countermeasure determining apparatus as described.

(Appendix 5)
As the circuit information, information on the correspondence table of voltage and current at the time of driver pull-down, information on correspondence table of voltage and current at the time of driver pull-up, and the power supply voltage value of the driver are used.
A first saturation current determining means for determining a current value corresponding to a voltage value equal to the power supply voltage value of the driver from a correspondence table of the voltage and current at the time of pulling down the driver and determining as a saturation current value at the time of pulling down;
A second saturation current determination means for determining a current value corresponding to a voltage value of 0 volts from a correspondence table of voltage and current at the time of pull-up of the driver and determining as a saturation current value at the time of pull-up;
And third saturation current value determining means for determining a smaller one of the saturation current values determined by the first and second saturation current determining means as the saturation current value of the driver. Yes (Appendix 3) The noise countermeasure determining device.

(Appendix 6)
A noise countermeasure determining apparatus that inputs circuit information of a target circuit and determines a noise countermeasure method for suppressing noise within a range in which an electronic circuit normally operates in a one-to-two transmission circuit,
As the circuit information, the equivalent capacitance value of two receivers and the characteristic impedance value of one transmission line are used, and from these input information, the load balance of the other transmission line that makes the electronic circuit operate normally is determined. A noise countermeasure determining apparatus comprising noise countermeasure determining means for determining a characteristic impedance value.

(Appendix 7)
On the computer,
As circuit information, the allowable range of the voltage at the receiver where the electronic circuit operates normally, the power supply voltage value of the driver, the characteristic impedance value of the transmission line, and the internal resistance value of the driver are used. A computer-readable recording medium on which a program for realizing a function of a noise countermeasure determining unit that suppresses noise and determines a damping resistance value range in which an electronic circuit operates normally as a noise countermeasure method is recorded.

(Appendix 8)
On the computer,
As circuit information, the allowable range of the voltage at the receiver where the electronic circuit operates normally, the power supply voltage value of the driver, the characteristic impedance value of the transmission line, and the internal resistance value of the driver are used. A program for realizing the function of a noise countermeasure determining unit that suppresses noise and determines a damping resistance value range in which an electronic circuit operates normally as a noise countermeasure method.

(Explanation of effects of invention in appendix)
(a): In (Appendix 4), the first internal resistance value deciding means uses the voltage-current correspondence table in the pull-up as the internal resistance value in the pull-up from the driver voltage-current correspondence table. The internal resistance value near the current 0 ampere is obtained. Next, the second internal resistance value determining means determines the internal resistance value in the vicinity of 0 ampere of current in the pull-down voltage-current correspondence table as the internal resistance value at the pull-down time from the driver voltage-current correspondence table. Ask for. Then, the third internal resistance value determining means obtains the larger one of the two obtained internal resistance values as the internal resistance value of the driver.

  By obtaining the internal resistance value of the driver in this manner, the noise countermeasure with high accuracy can be determined in the device of (Appendix 1) or (Appendix 3), so that the design man-hour is reduced as compared with the conventional case. it can.

  (b): In (Appendix 5), the first saturation current determination means obtains a current value corresponding to the voltage value equal to the power supply voltage value of the driver from the voltage-current correspondence table at the time of pull-down of the driver, and pulls it down. It is determined as the saturation current value at the time. The second saturation current determining means obtains a current value corresponding to a voltage value of 0 volts from the voltage-current correspondence table at the time of pull-up of the driver, and determines it as the saturation current value at the time of pull-up. Then, the third saturation current value determining means determines the smaller one of the saturation current values determined by the first and second saturation current determining means as the saturation current value of the driver.

  By obtaining the saturation current value of the driver in this way, it is possible to determine a more accurate noise countermeasure in the apparatus of (Appendix 3), so that the design man-hour can be reduced as compared with the conventional case.

It is a principle explanatory view of the present invention. 1 is a block diagram of a noise countermeasure determining apparatus according to an embodiment of the present invention, in which FIG. A is a basic configuration diagram of the apparatus, and FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the circuit structure in embodiment of this invention, A figure is explanatory drawing of a driver / receiver, B figure is explanatory drawing of 1 to 1 transmission, C figure is explanatory drawing of 1 to 2 transmission. FIG. 7 is an explanatory diagram of a correspondence table in the embodiment of the present invention, where FIG. A is an explanatory diagram of a correspondence table of voltage and current at the time of pull-up, and FIG. FIG. 5 is an example of a correspondence table in the embodiment of the present invention, in which FIG. A is a correspondence table example of voltage and current at the time of pull-up, B is a correspondence table example of voltage and current at the time of pull-down, and FIG. FIG. D shows relationship table example 2. It is a process flowchart of Example 1 in an embodiment of the invention. It is a processing flowchart of Example 2 in an embodiment of the invention. It is a processing flowchart of Example 3 in an embodiment of the invention. It is a processing flowchart (the 1) of example 4 in an embodiment of the invention. It is a processing flowchart (the 2) of example 4 in an embodiment of the invention. It is a process flowchart of Example 5 in an embodiment of the invention. FIG. 9 is a processing flowchart of Example 6 in the embodiment of the present invention, where FIG. A is a one-to-two transmission explanatory diagram, and FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit information storage part 2 Noise countermeasure determination processing part 3 Noise countermeasure information storage part 4 Database 11 Computer main body 12 Display apparatus 13 Input device 14 Removable disk drive 15 Magnetic disk apparatus 16 Printer 17 CPU (central processing unit)
18 ROM (Read Only Memory)
19 Memory 20 Interface control unit (I / F control unit)
21 Communication control unit

Claims (2)

A circuit information storage unit that stores circuit information that has been created in advance, and a database that stores a circuit constant relationship table that defines the relationship between circuit information,
Noise countermeasures for suppressing noise in a range in which an electronic circuit normally operates in a one-to-one transmission circuit by inputting circuit information of a target circuit from the circuit information storage unit and referring to information in the database A noise countermeasure determining device for determining a method,
As the circuit information, using the internal resistance value of the driver, the saturation current value of the driver, and the power supply voltage value of the driver, from these input information,
By subtracting the internal resistance value of the driver from the value obtained by dividing the power supply voltage value of the driver by the saturation current value of the driver, the electronic circuit operates normally at the receiver by setting the minimum value of the characteristic impedance of the transmission line. A noise countermeasure determining device comprising noise countermeasure determining means for determining, as a noise countermeasure method, a minimum value of characteristic impedance of a transmission line that becomes a voltage to be transmitted. A circuit information storage unit that stores circuit information that has been created in advance, and a database that stores a circuit constant relationship table that defines the relationship between circuit information,
By inputting circuit information of a target circuit from the circuit information storage unit and referring to the circuit constant relation table , noise for suppressing noise within a range in which an electronic circuit normally operates in a one-to-two transmission circuit A noise countermeasure determining device for determining a countermeasure method,
As the circuit information, the equivalent capacitance value of the receiver of one of the transmission line, using the equivalent capacitance value of the receiver of the other transmission line, the characteristic impedance of the transmission circuit of the one, from the input information, the one By obtaining the product of the equivalent capacitance value of the receiver of the transmission line and the one characteristic impedance value divided by the equivalent capacitance value of the receiver of the other transmission line as the characteristic impedance value of the other transmission circuit , A noise countermeasure deciding device comprising noise countermeasure deciding means for deciding a characteristic impedance value of the other transmission circuit so as to provide a load balance at which the electronic circuit operates normally.

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