# US 5,703,798 A · Switch level simulation employing dynamic short-circuit ratio > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,798 A - Document ID: US5703798A - Status: Granted - Kind: A - Application number: 08/428,725 - Filed: 1995-04-25 - Granted: 1997-12-30 - Earliest claimed: 1995-04-25 - Assignees: Mentor Graphics Corporation - Inventors: Sanjay Dhar - Web page: https://patentgrep.com/patent/US5703798A ## CPC - G06F 30/33: Design verification, e.g. functional simulation or model checking - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A switch level simulator having switch level speeds with near the accuracy of a circuit level simulator. Circuit parameters such as peak current, delay, and charge are calculated by using a dynamic short-circuit ratio. In the preferred embodiment a computer having a processor and memory is used to run the circuit simulations. A lookup table is built which represents how the circuit parameters vary with a change in the dynamic short-circuit ratio. The dynamic short-circuit ratio is calculated by taking the ratio of a first resistance in a first circuit path switching OFF to a second resistance in a second circuit path switching on. The circuit paths might be a parallel or series set of transistors which need to be combined to form an effective resistance for each path. The calculated dynamic short-circuit ratio is then used in the lookup table to determine the parameters in question. ## Claims ### Claim 1 In a method of electronic circuit simulation wherein a plurality of transistors is modelled as a plurality of resistive switches, an improvement for estimating a transient current between power and ground with at least two of the transistors switching including modeling the transient current as a function of a dynamic short-circuit ratio defined as a ratio of a first resistance in a first circuit path switching OFF to a second resistance in a second circuit path switching ON. ### Claim 2 A method for determining a parameter of a circuit's operation using an analog simulation device, comprising the steps: building a table of values representing how the parameter varies with change in a dynamic short-circuit ratio; calculating the dynamic short-circuit ratio in the circuit, the dynamic short-circuit ratio being defined as a ratio of a first resistance in a first circuit path switching OFF to a second resistance in a second circuit path switching ON; and searching the table using the dynamic short-circuit ratio to determine the parameter. ### Claim 3 (depends on 2) The method of claim 2 wherein the parameter is current. ### Claim 4 (depends on 2) The method of claim 2 wherein the parameter is delay. ### Claim 5 (depends on 2) The method of claim 2 wherein the parameter is charge. ### Claim 6 (depends on 2) The method of claim 2 wherein the parameter includes current, delay, and charge. ### Claim 7 (depends on 2) The method of claim 2 which further includes entering values representative how the parameter varies with change in input slew, load capacitance, and driver size. ### Claim 8 (depends on 2) The method of claim 2 which further includes calculating the input slew, the load capacitance, and the driver size in the circuit. ### Claim 9 (depends on 2) The method of claim 2 wherein the analog simulation device is a switch level simulator. ### Claim 10 (depends on 7) The method of claim 7 wherein calculating the input slew includes considering a plurality of series and parallel components. ### Claim 11 (depends on 7) The method of claim 7 wherein the input slew for the series components is the maximum input slew of all inputs that are switching in a series path. ### Claim 12 (depends on 7) The method of claim 7 wherein the input slew for the parallel components is the minimum input slew of each path in parallel. ### Claim 13 (depends on 2) The method of claim 2 wherein the first and second circuit paths are formed from a plurality of transistors in parallel or series. ### Claim 14 A method for determining operational parameters including current, output delay, and charge of a circuit using a computer programmed to perform switch level analog simulation, comprising the steps of: building a table of values representative of how the current, delay, and charge vary with change in input slew, dynamic short-circuit ratio, and load capacitance, wherein the delay is modeled as a resistance multiplied by the load capacitance producing a product, the product being added to a no-load delay, wherein the resistance and no-load delay are functions of the dynamic short-circuit ratio and the input slew, and wherein the current and charge are functions of the dynamic short-circuit ratio, input slew, and the load capacitance; calculating the input slew, the dynamic short-circuit ratio, and the load capacitance in the circuit, wherein the dynamic short-circuit ratio is defined as a ratio of a first resistance in a first circuit path switching OFF to a second resistance in a second circuit path switching ON, and wherein the input slew for series components is a maximum input slew of all inputs that are switching in a series path and the input slew for parallel components is a minimum input slew of each path in parallel, and wherein the load capacitance is a sum of a plurality of capacitances over a plurality of nodes that are changing voltage levels; and indexing the table with input slew, the dynamic short-circuit ratio, and the load capacitance to determine current, delay, and charge. ### Claim 15 In a simulation method wherein a computer is programmed to simulate operation of an electronic circuit and determine operational parameters therefrom, an improvement including using a dynamic short-circuit ratio in determining a parameter in the simulated electronic circuit, said dynamic short-circuit ratio being defined as a ratio of a first resistance in a first circuit path switching OFF to a second resistance in a second circuit path switching ON. ### Claim 16 (depends on 15) The simulation method of claim 15 wherein the parameter is charge. ### Claim 17 (depends on 15) The simulation method of claim 15 wherein the parameter is current. ### Claim 18 (depends on 15) The simulation method of claim 15 wherein the parameter is delay. ### Claim 19 (depends on 15) The simulation method of claim 15 in which the simulation method is a switch level simulation technique. ### Claim 20 In a method of electronic circuit simulation wherein a plurality of transistors is modelled as a plurality of resistive switches, an improvement for determining a delay parameter with at least two of the transistors switching, including modeling the delay as a function of a dynamic short-circuit ratio defined as a ratio of a first resistance in a first circuit path switching OFF to a second resistance in a second circuit path switching ON. ### Claim 21 A method of estimating a transient current between power and ground in a circuit having a pull-up portion and a pull-down portion, the transient current occurring with the pull-up and pull-down portions switching substantially simultaneously, the method comprising the steps of: determining a first resistance value for the pull-up portion of the circuit; determining a second resistance value for the pull-down portion of the circuit; and estimating the transient current as the combination of current flowing through one of the pull-up and pull-down portions that is switching OFF and current flowing through the other one of the pull-up and pull-down portions that is switching ON, the combination of current being estimated as a function of the ratio of the first and second resistance values. ### Claim 22 (depends on 21) The method of claim 21 including switching OFF the pull-up portion of the circuit and switching ON the pull-down portion of the circuit and estimating the transient current as a function of the first resistance value divided by the second resistance value. ### Claim 23 (depends on 21) The method of claim 21 including switching ON the pull-up portion of the circuit and switching OFF the pull-down portion of the circuit and estimating the transient current as a function of the second resistance value divided by the first resistance value. ### Claim 24 (depends on 21) The method of claim 21 including estimating a delay in switching the pull-up and pull-down portions of the circuit as a function of the ratio of the first and second resistance values.