Cell instance charge model for delay calculation
AssigneeCadence Design Systems, Inc.
InventorsIgor Keller, Xiaopeng Dong, Sourabh Rajguru
Life of this patent
Estimating the term…
Abstract
Various embodiments provide a charge model for a cell instance for delay calculation of a circuit design that includes the cell instance, where the charge model can be part of electronic design automation (EDA) and used in timing analysis of a circuit design that includes the cell instance. The charge model generated by an embodiment can predict a charge at an input of a cell instance for an arbitrary input voltage waveform and can address (e.g., reduce or negate) a time delay impact the Miller effect has on the cell instance.
Claims20
A non-transitory computer-readable medium comprising instructions that, when executed by a hardware processor of a device, cause the device to perform operations comprising:
- receiving a selection of a cell instance to generate a charge model for an input of the cell instance;
- accessing waveform data for the input of the cell instance, the waveform data describing a plurality of waveforms for the input corresponding to different slews at the input;
- accessing input capacitance data for the input of the cell instance, the input capacitance data describing a plurality of capacitance values at the input as a function of at least one of a voltage level at the input, slew at the input, or a load at an output of the cell instance;
- generating a plurality of equations based on a formulation of the charge model, the waveform data, and the input capacitance data;
- generating a fitted charge model for the input by determining a set of values for a set of parameters of the plurality of equations;
- and
- storing the set of values for the set of parameters for use in performing timing analysis of a circuit design that includes the cell instance.
A device comprising:
- a memory storing instructions;
- and
- a hardware processor communicatively coupled to the memory and configured by the instructions to perform operations comprising:
- accessing waveform data for an input of a cell instance, the waveform data describing a plurality of waveforms for the input corresponding to different slews at the input;
- accessing input capacitance data for the input of the cell instance, the input capacitance data describing a plurality of capacitance values at the input as a function of at least one of a voltage level at the input, slew at the input, or a load at an output of the cell instance;
- generating a plurality of equations based on a formulation of a charge model for the input of the cell instance, the waveform data, and the input capacitance data;
- generating a fitted charge model for the input by determining a set of values for a set of parameters of the plurality of equations;
- and
- storing the set of values for the set of parameters for use in performing static timing analysis of a circuit design that includes the cell instance.
A method comprising:
- accessing, by a hardware processor, waveform data for an input of a cell instance, the waveform data describing a plurality of waveforms for the input corresponding to different slews at the input;
- accessing, by the hardware processor, input capacitance data for the input of the cell instance, the input capacitance data describing a plurality of capacitance values at the input as a function of at least one of a voltage level at the input, slew at the input, or a load at an output of the cell instance;
- generating, by the hardware processor, a plurality of equations based on a formulation of a charge model for the input of the cell instance, the waveform data, and the input capacitance data;
- generating, by the hardware processor, a fitted charge model for the input by determining a set of values for a set of parameters of the plurality of equations;
- and
- using, by the hardware processor, the set of values for the set of parameters with a charge prediction equation to calculate a timing delay for a circuit design that includes the cell instance, the charge prediction equation comprising the set of parameters.
Dependencies are inferred from the claim text.