Switch level simulation employing dynamic short-circuit ratio

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.

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.

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.