JP2002149733A - Wiring designing method and designing support device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically design wiring specifications and their driving parameters by using a printed wiring designing support device without performing comprehensive transmission line simulation. SOLUTION: According to a net list including circuit information, additional information including driving condition information of an electronic device used to design a circuit and a device library including element information of the electronic device, a calculating means 11 calculates driving source voltage V1, driving source internal resistance R1, and a load model; a calculating means 12 calculates total load capacity C; a calculating means 13 calculates a load current i2; a calculating means 14 calculates a driving current i1; a calculating means 15 calculates wiring characteristic impedance Z and damping resistance R2; and a calculating means 16 calculates wiring width (w), so that wiring is carried out with the proper wiring width and dumping resistance value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring design method and a design support apparatus for a printed wiring board or the like used for electronic equipment such as information equipment.

[0002]

2. Description of the Related Art In a printed wiring board on which a digital circuit is mounted, as the frequency of a clock signal and each signal operating in synchronization with the clock signal increases, control of signal wiring for determining signal quality becomes important. It is well known that signal quality depends on the characteristic impedance of the printed wiring.

[0003] In practice, a digital signal needs to transition between two voltage levels indicating logical values of "0" and "1" at a sufficiently early time. Generally, logical value "0"
Is defined as a rise time, and a transition time in a reverse direction is defined as a fall time. However, these values are almost equal in a general digital IC. In this specification, both are generally referred to as a rise time.

In a digital circuit, a rise time, and a voltage undershoot and a voltage overshoot at the time of transition, must satisfy the operating specifications of an electronic device to be used. When the voltage undershoot or the voltage overshoot is large, a method of adding a damping resistor or a filter to smooth the rising and falling of the signal is used.

In order to satisfy these signal qualities, it is generally said that a comprehensive simulation of transmission line parameters is required at the pre-layout stage in designing a high-speed bus. Actually, in the pre-layout stage, only the comparison of the topology with the wiring specification and the damping resistance value as the specified values and the determination of the necessity of the buffer are performed, and the parameters are repeatedly adjusted in the post-layout verification. Nevertheless, it is not uncommon for hundreds of cases of simulation to be required for one board prototype, and reducing the number of simulations is a major issue in reducing the design / prototype period and the development cost.

In printed wiring design, it is ideal if the driving conditions such as wiring specifications and damping resistance can be automatically determined without such an exhaustive simulation. Has not been realized.

As a technique for determining the specifications of wiring by a printed wiring design apparatus, there is a method disclosed in Japanese Patent Application Laid-Open No. 11-96202. This method first calculates the current value flowing through each branch of the power supply wiring, temporarily determines the line width of the power supply wiring from the current value, and then calculates the line impedance from the voltage drop value determined by the line width. Then, a voltage drop value is determined from the impedance of the line, the wiring length, and the current value flowing through the branch portion, and it is determined whether or not the power supply voltage at the terminal satisfies the design allowance. The set line width is set as the line width of the power supply wiring.
However, this method is limited to the power supply wiring, and the specification of the signal wiring cannot be determined based on the signal quality.

In the technique disclosed in Japanese Patent Application Laid-Open No. 9-185644, a signal for identifying a current value is added to net information, and the conductor thickness, material, and allowable temperature rise value of a pattern are input as parameters. Then, the pattern width is calculated based on the current value and the current value, and wiring is performed based on the calculated pattern width. However, this method, as above,
The specifications of the signal wiring cannot be determined based on the signal quality.

In the technique disclosed in Japanese Patent Application Laid-Open No. Hei 10-21428, the parameter deriving first means derives an unknown design parameter from a known design parameter using a rule regarding the design parameter, and obtains a parameter deriving second means. Is to generalize a wiring design scheme in which an unknown design parameter is derived from a known design parameter using an expression including a design parameter. However, this method does not show any specific relationship between the index of the wiring specification and the design parameter.

[0010]

In a printed wiring design apparatus, it is ideal if driving conditions such as wiring specifications and damping resistance values can be automatically determined without using an exhaustive simulation. A method for determining these conditions has not been realized conventionally. Actually, the wiring specification and the damping resistance value are also treated as variables like the wiring length and the topology, so that the number of simulations is increased by n times.

As a result of a study by the present inventors, it has been found that basic wiring and drive parameters can be automatically determined from required specifications of signal quality and load conditions. Therefore, the present invention provides a design method and a design support apparatus for automatically determining basic wiring and drive parameters from a circuit diagram and a required specification of signal quality in a printed wiring design and performing artwork. The purpose is to provide. Further objects of the present invention will be apparent in the following description.

[0012]

SUMMARY OF THE INVENTION The present invention derives a practical wiring design method by clarifying its physical meaning based on a formulation based on empirical knowledge of artwork design. FIG. 2 shows a model of a driving source 1, a transmission line 2, and a load 3 relating to signal wiring of a general printed circuit board. The drive source voltage V1 is a clamp voltage of a power supply in which an output of the driver 1 as a drive source supplies a current to the load device 3 in a logic manner. A load device 3 is connected to this drive source driver 1 via a damping resistor R2 and a transmission line 2.
Are connected.

If the wiring forming the transmission line 2 is a microstrip wiring coupled to the ground plane of the substrate, the current propagates while charging the distributed capacitance between the wiring pattern and the ground plane. For example, a high impedance input element such as a CMOS is regarded as a capacitive load. For this load capacitance C, a condition for raising the load voltage V3 at the rise time tr is determined. That is, first, the current i2 flowing through the load capacitance is set according to i2 × tr = C × V3. here,
The value of the load current i2 does not match the input current i1 to the wiring 2 due to charging and discharging of the wiring capacitance. As a result of the study by the inventor, it has been found that this relationship substantially depends only on the rise time tr, regardless of the load capacitance value, as shown in FIG.

Further, when the propagation time of the wiring 2 is sufficiently long with respect to the rise time of the voltage V1 of the driving source 1,
I1 immediately after rising is as follows: i1 = V1 / (R1 + R2 + Z). Note that i1 is a drive current output from the drive source 1, R1 is an internal resistance of the drive source 1, R2 is a damping resistance, and Z is a characteristic impedance of the wiring 2.

For this drive current i1, the characteristic impedance Z of the wiring is determined from the condition of stabilizing the load voltage. The output voltage first rises to V2 = Z × i1. The load voltage V3 fluctuates up to twice the worst case due to signal reflection such as a mismatched termination bus. The characteristic impedance Z is set so that the fluctuation range of the load voltage V3 matches the input condition of the load element. Further, for the driving source 1 whose internal resistance R1 is known,
The damping resistance R2 is automatically determined from the equation regarding i1.

The relationship between wiring specifications and characteristic impedance is
Formulated for various wirings. For example, Wheele
r, Harold A., “Transmission-Line Properties of a S
trip Line on a Dielectric Sheet on a Plane, ”IEEE
Transactions on Microwave Theory and Techniques,
From the equation shown in Vol. MTT-25, No. 8, p631, August 1977, it is possible to determine the specifications of the microstrip wiring for the desired characteristic impedance. FIG.
This shows the relationship between the wiring specifications (wiring width w and interlayer distance h) and the characteristic impedance Z of the wiring for a typical structure used in a general printed wiring board.

Therefore, according to the present invention (claim 1), based on the result of the research by the present inventor, the drive source electronic device and the load electronic device driven by the drive source electronic device are connected by wiring. A method of designing an electronic circuit, using a relationship between a ratio of a drive current for charging a wiring when a drive source electronic device is driven and a load current for charging a load device, and a voltage rise time in the load device, A wiring design method comprising calculating an output impedance of a drive source device and a characteristic impedance of a wiring.

[0018] The present invention (claim 8) is a design support apparatus for implementing the above-described wiring design method. According to the present invention described above, it is possible to automatically determine wiring specifications based on data output from an electronic circuit design device. That is, the printed wiring design apparatus can automatically determine the wiring specifications based on the data obtained by the printed wiring design method and the data output from the printed wiring design support apparatus. That is, it is possible to automatically and top-down design the wiring specifications and their driving parameters without relying on the comprehensive manual transmission line simulation of the pre-layout conventionally performed manually.

Further, the present invention (claim 2) provides a device list including a netlist including circuit information, accompanying information including driving condition information of an electronic device used for designing a circuit, and specification information of the electronic device. A load model including input load capacitance characteristic information of the electronic device to be driven, a drive source voltage of the electronic device, and an internal resistance of a drive source for driving the electronic device. Calculating the sum of the load capacities of the electronic devices driven by the driving source based on the calculated load model, the design value of the rise time of the load voltage applied to the driven electronic device, and the calculated total load of the electronic device. Based on the capacitance, a load current applied to the electronic device is calculated, and a design value of a rise time of a load voltage applied to the driven electronic device is calculated. A drive current output from the drive source is calculated based on the calculated load current applied to the electronic device, and the total resistance on the drive source side is calculated based on the calculated drive current and the calculated drive source voltage. And the characteristic impedance of the wiring connecting the drive source and the driven electronic device, and based on the layer configuration, metal thickness, interlayer distance, and material of the printed circuit board on which the wiring is provided, the wiring having the characteristic impedance of the wiring The width is calculated, and the damping resistance on the drive source side is calculated based on the calculated total resistance on the drive source side and the calculated internal resistance on the drive source, and wiring is performed with an appropriate wiring width and damping resistance value. This is the wiring design method.

Further, the present invention (claim 9) is a design support apparatus for implementing the above wiring design method. According to the present invention described above, it is possible to automatically determine wiring specifications based on data output from an electronic circuit design device. That is, the printed wiring design apparatus can automatically determine the wiring specifications based on the data obtained by the printed wiring design method and the data output from the printed wiring design support apparatus. That is, it is possible to automatically and top-down design the wiring specifications and their driving parameters without relying on the comprehensive manual transmission line simulation of the pre-layout conventionally performed manually.

In the wiring design method according to the present invention (claim 3), in addition to the above, the output impedance or the output buffer element of the drive source device is selected so as to have the calculated total resistance on the drive source side. The way things are. That is, for a drive source device or an output buffer element whose output buffer characteristics can be selected, an output impedance or an output buffer of the drive source device is automatically selected so as to have the drive source total resistance. In the same manner as in the invention, wiring is automatically performed with an appropriate wiring width. According to the present invention, the characteristics of the drive system, which have been selected based on the manual simulation, are automatically selected.

Further, in addition to the above, the wiring design method according to the present invention (claim 4) provides a rise time design value that defines a relationship among a load current, a drive current, and a design value of a rise time of a load voltage. The load current is calculated based on the regression equation regarding the load current. That is, the present invention is characterized in that the load current value is calculated based on a regression equation based on the design value of the rise time. According to the present invention, the load current value can be determined without referring to the transmission line simulation by calculating the load current value based on the regression equation based on the rise time design value.

[0023] In addition to the above, the wiring design method according to the present invention (claim 5) may further include, based on the load capacitance of the electronic device driven by the drive source, with respect to the length of the wiring having the calculated width. Thus, the calculated characteristic impedance of the wiring is corrected. That is, the characteristic impedance of the wiring and the total resistance on the driving source side are corrected based on the wiring length of the wiring. According to the present invention, an optimum wiring specification can be obtained for each wiring length.

Here, such correction is performed for the following reason. FIG. 5 shows three types of load capacitances (20 pF, 40 pF, and 80 pF) with wiring having a characteristic impedance Z = 50Ω.
4F shows the relationship between the wiring length and the factors in FIG. In a region where the wiring length is short, an error occurs due to the lumped constant behavior of the wiring, so that correction is necessary. The wiring length that needs to be corrected differs depending on the load capacitance as can be seen from FIG. This is because the voltage rise time of the load depends on the load capacity. FIG. 6 shows the minimum length that does not require correction for the rise time and the total load capacity.

Further, according to the wiring design method of the present invention (claim 6), a net list including circuit information, accompanying information including driving condition information of an electronic device used for designing a circuit, and specifications of the electronic device Based on the device library including the information, the load model including the input load capacitance characteristic information of the electronic device to be driven, the drive source voltage of the electronic device, and the internal resistance of the drive source for driving the electronic device are calculated. Then, the sum of the load capacities of the electronic devices driven by the drive source is calculated based on the device library and the calculated load model, and the design value of the rise time of the load voltage applied to the driven electronic device and the calculated value are calculated. The load current applied to the electronic device is calculated based on the total load capacity of the electronic device, and the rise of the load voltage applied to the driven electronic device is calculated. The drive current output from the drive source is calculated based on the design value of the drive time and the calculated load current applied to the electronic device, and based on the calculated drive current and the calculated drive source voltage. , The total resistance on the drive source side and the first characteristic impedance of the wiring connecting the drive source and the electronic device to be driven are calculated, and the layer configuration, metal thickness, wiring width, interlayer When the second characteristic impedance due to the distance and the material is larger than the calculated first characteristic impedance, the minimum total driving-source-side resistance is selected, and the layer configuration, metal thickness, wiring width, wiring width, Wire with the interlayer distance and material.

That is, in the present invention, the second characteristic impedance based on the layer structure, metal thickness, wiring width, interlayer distance, and material of the printed circuit board given in advance is larger than the required value of the characteristic impedance obtained by calculation. If the minimum drive source side total resistance is selected, and the matching termination is automatically inserted into the netlist, the predetermined printed circuit board layer configuration, metal thickness,
Wiring is performed according to the wiring width, interlayer distance, and material. According to the present invention, when a sufficiently fast rise time cannot be obtained with the required value of the transient response of the signal waveform in the wiring specification given in advance, the drive is performed with a low output impedance to increase the rise time, and the transient termination is performed by the matching termination. Can be suppressed.

Further, according to the wiring design method of the present invention (claim 7), a netlist including circuit information, accompanying information including driving condition information of an electronic device used for designing a circuit, and specifications of the electronic device Based on the device library including the information, the load model including the input load capacitance characteristic information of the electronic device to be driven, the drive source voltage and the internal resistance of the drive source electronic device are calculated, and the device library is calculated. The sum of the load capacities of the electronic devices driven by the driving source is calculated based on the load model, and the sum of the design values of the rise time of the load voltage applied to the driven electronic device and the calculated total load capacities of the electronic devices are calculated. The load current applied to the electronic device is calculated, and the design value of the rise time of the load voltage applied to the driven electronic device is calculated. A drive current output from the drive source is calculated based on the load current applied to the slave device, and the total resistance on the drive source side is calculated based on the calculated drive current and the calculated drive source voltage. The first characteristic impedance of the wiring connecting the source and the electronic device to be driven is calculated, and the second characteristic impedance according to the layer configuration, metal thickness, wiring width, interlayer distance and material of the printed circuit board given in advance is calculated. If the calculated first characteristic impedance is smaller than the calculated first characteristic impedance, the driving source-side damping resistance is selected so that the total resistance on the driving source side has a value equal to the second characteristic impedance, and the layer configuration of the printed circuit board is given in advance. Wire according to metal thickness, wiring width, interlayer distance and material.

That is, according to the present invention, the second characteristic impedance based on the given layer configuration, metal thickness, wiring width, interlayer distance, and material of the printed board is sufficiently larger than the required value of the characteristic impedance obtained by calculation. If it is low, it automatically selects the output matching.
It is possible to obtain a calculation result that does not cause a problem of a transient response while guaranteeing a sufficient rise of a signal waveform.

[0029]

FIG. 1 shows a configuration of a printed wiring design support apparatus according to an embodiment of the present invention. The design support apparatus uses a computer support resource such as a processor or a memory to provide a design support program. To execute the printed wiring design method according to the present invention. In the following description, the model shown in FIG.

This printed wiring design support equipment has calculating means 11 to 16 and relates to a printed wiring design obtained from an input means 18 such as a user interface and a device library 19 configured in a memory or the like. Based on the information, the width w of the wiring 2 as a transmission line formed on the printed board and the damping resistance value R2 of the drive source device 1 are calculated.

The first calculating means 11 obtains from a device library 19 a netlist including circuit information obtained from the input means 18 and accompanying information including driving condition information of an electronic device used for designing the circuit. A load model including input load capacitance characteristic information of the electronic device 3 to be driven, a drive source voltage V1 of the electronic device, and a drive source for driving the electronic device based on the specification information of the electronic device. The internal resistance R1 is calculated. That is, based on the netlist and the accompanying information specified by the designer, the drive source voltages V1,
A process for extracting the drive source internal resistance R1 and the load model is performed.

The second calculating means 12 calculates the total sum of the load capacities C of the electronic devices driven by the drive source 1 based on the device library 19 and the load model obtained by the first calculating means 11. The third calculating means 13 supplies the electronic device 3 based on the total load capacitance C obtained by the second calculating means 12 and the design value Tr of the rise time of the load voltage V3 applied to the driven electronic device. The added load current i2 is calculated. That is, the above relational expression i2 × t
Using r = C × V3, the load current i2 is calculated from the total load capacitance C and the rise time design value Tr. It should be noted that the design value Tr of the rise time is input as to whether it is obtained from the operation specifications or calculated based on the operation frequency.

The fourth calculating means 14 is the third calculating means 1
The load current i2 obtained in Step 3 and the rise time design value Tr
The drive current i1 output from the drive source 1 is calculated based on the above. That is, as shown in FIG.
Using the relationship that the ratio between the load current i2 and the rise time design value Tr depends on the relationship that the ratio between the load current i2 and the load current i2 substantially depends only on the rise time tr regardless of the load capacitance value.
1 is calculated.

The fifth calculating means 15 includes the first calculating means 1
1 and the drive source internal resistance R1
And the driving current i1 obtained by the fourth calculating means 14 to calculate the damping resistance R2 on the driving source side and the characteristic impedance Z of the wiring 2 connecting the driving source and the electronic device to be driven. . That is, the above-mentioned relational expression i1
= V1 / (R1 + R2 + Z), and a relational expression Z that defines the relationship between the drive current i1, the wiring characteristic impedance Z, and the voltage.
= V1 '/ i1 to obtain a damping resistor R2 from the drive source voltage V1, the drive source internal resistance R1, and the drive current i1.
And the wiring characteristic impedance Z are calculated.

Here, as shown in FIG. 3, the driving current i1
The ratio between the load current i2 and the load current i2 becomes a certain constant k when the rise time design value Tr is determined. However, if the drive source voltage V1 'is set so that the variation range of the load voltage V2 matches the input condition of the load element. , I2 / i1 = drive current i1 set by k
The wiring characteristic impedance Z can be obtained by the relational expression Z = V1 '/ i1. Note that the driving source voltage V1
'Is obtained from the device library 19.

The sixth calculating means 16 calculates the characteristic impedance Z obtained by the fifth calculating means 15 based on the layer configuration of the printed circuit board, the thickness of the wiring metal, the interlayer distance and the material set by the designer. The wiring width w to be calculated is calculated. That is, as shown in FIG. 4, based on the layer configuration of the printed circuit board (microstrip, facing strip, strip, asymmetric strip, etc.), the thickness t of the wiring metal, the interlayer distance h, and the material (dielectric constant, etc.). , The width w of the wiring metal is calculated. Therefore, the appropriate wiring width w and damping resistance value R2 calculated as described above are described in the netlist, and the wiring of the printed circuit board having the expected performance can be performed based on the netlist.

FIG. 7 shows an outline of a more specific operation of the printed wiring design support apparatus. First, the current i1 from the driving element is calculated based on the above relational expressions. If the current i1 exceeds the rating of the driving element, a buffer is added or the element is changed. Further, the impedance Z and the damping resistance value R2 are calculated, and when the calculated value of the damping resistance becomes a negative value, a buffer having a small output impedance is added or the driving element is changed.

FIG. 7 also shows an outline of the operation of the printed wiring design method according to the second aspect of the present invention. The output impedance or output buffer element of the drive source device 1 is automatically selected so as to have the drive source total resistance R1 + R2. If a sufficient output resistance cannot be obtained, R2 is calculated and added to the netlist. If R2 is already in the netlist and calculated as unnecessary, it is deleted. For the function of selecting the output characteristics based on the load specifications or the function of selecting an appropriate driver from the candidates, there are those that can select the output characteristics of the device by software or wire settings, such as recent microprocessors. The one that sets the value based on the calculation result according to the present invention is also included. At this time, it is needless to say that the necessity / unnecessity of the damping resistor is determined.

According to the invention of claim 3, as the regression equation, for example, the following equation of an approximate curve shown on the graph of FIG. 3 can be used. Further, in mounting on a printed wiring design device, a table and its interpolation value can be used.

[0040]

(Equation 1)

FIG. 8 shows an outline of the operation of the printed wiring design according to the fourth aspect of the present invention. As a method of correcting the characteristic impedance Z of the wiring and the total resistance R1 + R2 of the driving source with respect to the wiring length, a method of correcting the calculated value of the load capacitance by using the curve shown in the graph of FIG. This is performed using If the approximate arrangement of components and the approximate wiring length are determined in advance, it is also possible to perform correction based on the wiring length in advance when calculating the drive current i1.

FIG. 9 shows an outline of the operation of the printed wiring design according to the fifth aspect of the present invention. If the characteristic impedance calculated as described above is larger than the second characteristic impedance as a required value according to the layer configuration, metal thickness, wiring width, interlayer distance, and material of the printed circuit board given in advance, the minimum driving source Selecting the total resistance and automatically inserting matching terminations into the netlist,
Wiring is performed according to the given layer configuration, metal thickness, wiring width, interlayer distance, and material of the printed circuit board. If it is determined that the rise time is further insufficient in this way, it is possible to make an indication to change the specifications such as the wiring width.

[0043]

As described above, according to the present invention,
Wiring specifications and drive parameter design are automatically performed based on data output from the electronic circuit design device using a printed wiring design support device, instead of the comprehensive manual transmission line simulation of printouts conventionally performed manually. It is possible to do. Therefore, it is not necessary to perform a pre-layout transmission line simulation for a large number of parameters before the artwork, and it is possible to drastically shorten the design period.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a printed wiring design support apparatus according to an example of the present invention.

FIG. 2 is a conceptual diagram of a printed wiring circuit model.

FIG. 3 is a graph showing a relationship between a ratio between a drive current and a load current and a rise time.

FIG. 4 is a graph showing a relationship between characteristic impedance and specifications of substrate wiring.

FIG. 5 is a graph showing a relationship between a ratio of a drive current to a load current and a wiring length.

FIG. 6 is a diagram showing a relationship among a rise time, a total load capacity, and a minimum length of a wiring.

FIG. 7 is a diagram showing an outline of an operation process according to the present invention.

FIG. 8 is a diagram showing an outline of an operation process according to the present invention.

FIG. 9 is a diagram showing an outline of an operation process according to the present invention.

[Explanation of symbols]

1: drive source, 2: transmission line (wiring), 3: load device, V1: drive voltage, V3: load voltage, i1: drive current, i2: load current, R1: drive source internal resistance, R
2: damping resistance, Z: wiring characteristic impedance,
w: wiring width,

Claims (9)

[Claims] 1. A method for designing an electronic circuit in which a drive source electronic device and a load electronic device driven by the drive source electronic device are connected by wiring, wherein the drive source electronic device charges the wiring when driven. Calculating the output impedance of the drive source device and the characteristic impedance of the wiring by using the relationship between the ratio of the drive current to be charged to the load current for charging the load device and the voltage rise time at the load device. Wiring design method. 2. An electronic device to be driven based on a net list including circuit information, accompanying information including driving condition information of an electronic device used for designing a circuit, and a device library including specification information of the electronic device. A load model including input load capacitance characteristic information of the device, a drive source voltage and an internal resistance of the drive source electronic device are calculated, and a device library and an electronic device driven by the drive source based on the calculated load model are calculated. Calculate the sum of the load capacitances, calculate the load current applied to the electronic device based on the design value of the rise time of the load voltage applied to the electronic device to be driven, and the calculated total load capacitance of the electronic device. Based on the design value of the rise time of the load voltage applied to the target electronic device and the calculated load current applied to the electronic device, drive is performed. The drive current output from the source is calculated, and based on the calculated drive current and the calculated drive source voltage, the total resistance on the drive source side and the wiring of the drive source and the electronic device to be driven are connected. Calculate the characteristic impedance, calculate the wiring width having the characteristic impedance of the wiring based on the layer configuration, metal thickness, interlayer distance and material of the printed circuit board on which the wiring is provided, and calculate the calculated total resistance on the drive source side and A wiring design method of calculating a damping resistance on the driving source side based on the calculated internal resistance of the driving source and wiring with an appropriate wiring width and damping resistance value. 3. The wiring design method according to claim 2, wherein the output impedance or the output buffer element of the drive source device is selected so as to have the calculated total resistance on the drive source side. 4. The wiring design method according to claim 2 or 3, wherein a regression equation relating to a rise time design value that defines a relationship among a load current, a drive current, and a design value of a rise time of a load voltage. Wiring design method for calculating load current based on 5. The wiring design method according to claim 2, wherein a load length of the electronic device driven by the drive source is determined based on a length of the wiring having the calculated width. A wiring design method for correcting a calculated characteristic impedance of a wiring based on the wiring design. 6. An electronic device to be driven based on a netlist including circuit information, accompanying information including driving condition information of an electronic device used to design a circuit, and a device library including specification information of the electronic device. A load model including input load capacitance characteristic information of the device, a drive source voltage and an internal resistance of the drive source electronic device are calculated, and a device library and an electronic device driven by the drive source based on the calculated load model are calculated. Calculate the sum of the load capacitances, calculate the load current applied to the electronic device based on the design value of the rise time of the load voltage applied to the electronic device to be driven, and the calculated total load capacitance of the electronic device. Based on the design value of the rise time of the load voltage applied to the target electronic device and the calculated load current applied to the electronic device, drive is performed. The drive current output from the source is calculated, and based on the calculated drive current and the calculated drive source voltage, the total resistance on the drive source side and the wiring of the drive source and the electronic device to be driven are connected. The first characteristic impedance is calculated, and the second characteristic impedance due to the layer structure of the printed circuit board, the metal thickness, the wiring width, the interlayer distance, and the material given in advance is larger than the calculated first characteristic impedance, A wiring design method that selects the minimum total resistance on the drive source side and performs wiring based on the given layer configuration, metal thickness, wiring width, interlayer distance, and material of the printed circuit board. 7. An electronic device to be driven based on a netlist including circuit information, accompanying information including driving condition information of an electronic device used for designing a circuit, and a device library including specification information of the electronic device. A load model including input load capacitance characteristic information of the device, a drive source voltage and an internal resistance of the drive source electronic device are calculated, and a device library and an electronic device driven by the drive source based on the calculated load model are calculated. Calculate the sum of the load capacitances, calculate the load current applied to the electronic device based on the design value of the rise time of the load voltage applied to the electronic device to be driven, and the calculated total load capacitance of the electronic device. Based on the design value of the rise time of the load voltage applied to the target electronic device and the calculated load current applied to the electronic device, drive is performed. The drive current output from the source is calculated, and based on the calculated drive current and the calculated drive source voltage, the total resistance on the drive source side and the wiring of the drive source and the electronic device to be driven are connected. Calculating a first characteristic impedance, and when a second characteristic impedance based on a given layer configuration, metal thickness, wiring width, interlayer distance, and material of the printed circuit board is smaller than the calculated first characteristic impedance, The damping resistor on the drive source side is selected so that the total resistance on the drive source side has the same value as the second characteristic impedance, and the layer structure, metal thickness, wiring width, interlayer distance and material of the printed circuit board are determined in advance. Wiring design method to wire. 8. An apparatus for supporting the design of an electronic circuit in which a drive source electronic device and a load electronic device driven by the drive source electronic device are connected by wiring, wherein the drive source electronic device is connected to a wire when driven. Means for calculating the output impedance of the drive source device and the characteristic impedance of the wiring by using the relationship between the ratio of the drive current for charging the load device to the load current for charging the load device and the voltage rise time at the load device. A wiring design support device characterized by the following. 9. An electronic device to be driven based on a netlist including circuit information, accompanying information including driving condition information of an electronic device used to design a circuit, and a device library including specification information of the electronic device. A load model including input load capacitance characteristic information of the device; a unit for calculating a drive source voltage and an internal resistance of the drive source electronic device; a device library; and an electronic device driven by the drive source based on the calculated load model. Means for calculating the sum of the load capacities of the devices, the design value of the rise time of the load voltage applied to the driven electronic device, and the load current applied to the electronic device based on the calculated total load capacity of the electronic device. Means for calculating, a design value of a rise time of a load voltage applied to the driven electronic device, and a calculated value applied to the electronic device. Means for calculating a drive current output from the drive source based on the load current; a total resistance on the drive source side based on the calculated drive current and the calculated drive source voltage; Means for calculating the characteristic impedance of the wiring connecting to the electronic device to be driven; and calculating the wiring width having the characteristic impedance of the wiring based on the layer configuration, metal thickness, interlayer distance and material of the printed circuit board on which the wiring is provided. Means for calculating the damping resistance on the drive source side based on the calculated total resistance on the drive source side and the calculated internal resistance on the drive source. A wiring design support device that supports wiring by value.