# US 12,001,770 B2 · Analog centric current modeling within a digital testbench in mixed-signal verification

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- Number: US 12,001,770 B2
- Document ID: US12001770B2
- Status: Granted
- Kind: B2
- Application number: 15/658,308
- Filed: 2017-07-24
- Published: 2018-05-10
- Granted: 2024-06-04
- Earliest claimed: 2016-05-25
- Assignees: Synopsys, Inc.
- Applicants: Synopsys, Inc.
- Inventors: Vijay Akkaraju; David Francis Cronauer
- Web page: https://patentgrep.com/patent/US12001770B2

## CPC

- G06F 30/367: Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods
- G06F 30/33: Design verification, e.g. functional simulation or model checking
- G06F 30/3308: using simulation
- G06F 30/3312: Timing analysis
- G06F 30/38: Circuit design at the mixed level of analogue and digital signals
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A method includes operating a digital simulator to mimic loading effects of digital circuit blocks of a circuit design on analog circuit blocks of the circuit design. The digital simulator sets a current signal timing and a current level value at an analog/digital boundary between the digital circuit aspects and the analog circuit aspects. The analog simulator is operated to apply the current signal timing and the current level value to simulate the analog circuit blocks.

## Claims

### Claim 1

A computer-implemented method of testing a circuit design, the method comprising:
applying a test vector from a digital circuit simulator test bench stimulus to a digital simulation interface;
supplying a time varying first current signal from the digital simulation interface to an analog circuit simulator in response to the test vector the time-varying first current signal having a first value during a first point in time and a second value during a second point in time, the second value being different from the first value, the first point in time and the second point in time defining a first time interval, wherein the time-varying first current signal is representative of current loading characteristics of a first portion of the circuit design, wherein the first portion comprises digital circuits;
performing, by the analog circuit simulator, an analog simulation of a second portion of the circuit design using the time-varying first current signal;
measuring, by a measurement operation, a second current signal in response to the performed analog simulation of the circuit design;
supplying, by the measurement operation, the second current signal to a current status indicator via the digital simulation interface;
and causing the time-varying first current signal to change by the current status indicator, during a second time interval different from the first time interval, until the second current signal has a value that is equal to or less than a threshold value.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
supplying a first time-varying voltage supply signal to a digital circuit simulator.

### Claim 3 (depends on 2)

The method of claim 2, wherein the first time-varying voltage supply signal is supplied during a power-up or a power-down operation.

### Claim 4 (depends on 3)

The method of claim 3, wherein the first time-varying voltage supply signal is supplied by a first low-drop-out voltage circuit.

### Claim 5 (depends on 2)

The method of claim 2, further comprising supplying a second time-varying voltage supply signal to the digital circuit simulator in response to the time-varying first current signal and using a first low-drop-out voltage circuit.

### Claim 6

A computer system configured to test a circuit design, the computer system comprising:
a memory storing instructions;
and a processor, coupled with the memory and to execute the instructions, the instructions when executed cause the processor to:
apply a test vector from a digital circuit simulator test bench stimulus to a digital simulation interface;
supply a time varying first current signal from the digital simulation interface to an analog circuit simulator in response to the test vector, the time-varying first current signal having a first value during a first point in time and a second value during a second point in time, the second value being different from the first value, the first point in time and the second point in time defining a first time interval, wherein the time-varying first current signal is representative of current loading characteristics of a first portion of the circuit design, wherein the first portion comprises digital circuits;
perform, by the analog circuit simulator, an analog simulation of a second portion of the circuit design using the time-varying first current signal;
measure, by a measurement operation, a second current in response to the performed analog simulation of the circuit design;
supply, by the measurement operation, the second current signal to a current status indicator via the digital simulation interface;
and cause the time-varying first current signal to change by the current status indicator, during a second time interval different from the first time interval, until the second current signal has a value that is equal to or less than a threshold value.

### Claim 7 (depends on 6)

The computer system of claim 6, wherein the computer system is further configured to:
supply a first time-varying voltage supply signal to a digital simulator.

### Claim 8 (depends on 7)

The computer system of claim 7, wherein the first time-varying voltage supply signal is supplied during a power-up or a power-down operation.

### Claim 9 (depends on 8)

The computer system of claim 8, wherein the first time-varying voltage supply signal is supplied by a first low-drop-out voltage circuit.

### Claim 10 (depends on 7)

The computer system of claim 7, wherein the computer system is further configured to supply a second time-varying voltage supply signal to the digital simulator in response to the time-varying first current signal and using a first low-drop-out voltage circuit.