JPH0471072A - Method for simulating analog/digital mixed integrated circuit - Google Patents

Abstract

PURPOSE:To make it possible to describe the circuit data of one integrated circuit by a united description system by including circuit simulating primitive in an analog cell and making it possible to use the same data for both of circuit simulation data and layout circuit data. CONSTITUTION:The contents of the analog cell are described by the circuit simulating primitive, a circuit obtained by mixedly describing an analog circuit part 107 described by an analog cell to be laid out by a layout program 104 and a digital circuit part 108 is registered, and after developing the hierarchy and the cell mixing both analog and digital primitives, circuit simulation data and logical simulation data are mutually separated and respectively simulated. Consequently, the layout circuit of one analog/digital mixed LSI can be described and registered by the united description system.

Description

[Detailed Description of the Invention] [Summary] A method for verifying the design of an analog/digital hybrid integrated circuit having both an analog circuit section and a digital circuit section on a chip, the circuit data of one integrated circuit being unified. In order to verify the design of an analog/digital mixed integrated circuit that has both an analog circuit section and a digital circuit section on a single chip, the following method is used to describe the analog circuit section. In a simulation method of performing a circuit simulation and performing a logic simulation on the digital circuit section, the analog circuit section is described in which the inside of the cell is described as a primitive for circuit simulation and as an analog cell that can be laid out by a layout program, After registering the circuit described in combination with the digital circuit section, and expanding the hierarchy and cells by mixing analog primitives and digital primitives, the circuit simulation data and logic simulation data are separated by an analog/digital separation program. The configuration is such that the simulations are performed separately.

[Industrial application field]

The present invention relates to a simulation method for an analog/digital mixed integrated circuit, and more particularly to a method for verifying the design of an analog/digital mixed integrated circuit having both an analog circuit section and a digital circuit section on a chip.

In recent years, in order to increase the degree of integration and functionality of large-scale integrated circuits (LSIs), various attempts have been made to mix analog elements and digital elements that can coexist. In order to verify the design of such an analog/digital mixed LSI, a circuit simulator is required for the analog circuit section, and a logic simulator is required for the digital circuit section. However, since each of these simulators operates separately, it is only possible to check the entire circuit.

Therefore, there is a need for a simulation method that can verify the entire analog/digital hybrid circuit including other circuit sections at once, even if the circuit simulator and logic simulator are operated separately.

[Conventional technology]

FIG. 2 shows an explanatory diagram of an example of a conventional analog/digital mixed integrated circuit simulation method. Conventionally, analog/digital mixed layout circuits were divided into digital circuits and analog circuits, and for digital circuits, circuits described in logic simulation description were registered (1) in Figure (A), and for analog circuits, circuit simulation was performed. The circuit according to the description is registered (8 in the same figure (B)).

For example, the above-mentioned analog/digital mixed layout circuit, as shown in FIG. analog signal to D
From the A converter (DAC) 13, connect it to the resistor 14.
．． The signal is input to an AD converter (ADC) 19 through a circuit section consisting of an amplifier 15° resistor 16.17 and a capacitor 18, and a 2-bit digital output corresponding to the input signal level is taken out from this ADC 19, and 1 bit is sent to an inverter 2.
It is assumed that the circuit has a feedback loop, in which one bit is output to the outside via one bit, and the other bit is applied to the FF12.

In this case, the above AND circuit 11. The digital circuit section consisting of the FF 12 and the inverter 20 is registered as a logic simulation description circuit as shown in FIG. amplifier 1
5. The analog circuit section consisting of the capacitor 18 and the ADC 19 is registered as a circuit described in the circuit simulation as shown in FIG. However, in reality, the amplifier 15 is described at a circuit level consisting of transistors and resistors.

Here, as shown in FIG. 4, in the logic simulation description circuit, the DAC 3 is described by a dummy circuit consisting of AND circuits 21 and 22, and the ADC 19 is described by a dummy circuit consisting of inverters 23-26.

In FIG. 2 (A), the registered digital circuit (logical simulation description circuit) is then expanded into a user hierarchy (step 2) and stored in the database 3 of logical information expanded to the cell level. Then, cells are developed based on the layout circuit information 4 (step 5). In this way, the digital circuit information developed into a set of primitives that are simulation basic unit elements that can be simulated is registered in the memory (step 6), and then simulated by a logic simulator (step 7).

On the other hand, the registered analog circuit (circuit simulation description circuit) is simulated by a circuit simulator as shown in FIG. 2(B) (step 9). In this way, conventionally, the digital circuit section and the analog circuit section of an analog/digital hybrid circuit have been registered separately, and then logic simulation and circuit simulation have been performed separately for each.

[Problem to be solved by the invention]

However, conventionally, the analog circuit section is a circuit description for a circuit simulator, whereas the digital circuit section is a logic circuit description with the analog circuit section as a dummy circuit, and each circuit needs to be written for two simulators. one L
It was not possible to describe SI circuit data using a unified description method. Also, because the digital circuit section or the analog circuit section is described as a dummy circuit, the content differs from the layout data, and back annotations such as wiring capacitance from the layout result cannot be obtained.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a simulation method for an analog/digital hybrid integrated circuit that allows circuit data of one integrated circuit to be described using a unified description method.

[Means to solve the problem]

The method for simulating an analog/digital mixed integrated circuit according to the present invention is a method for simulating an analog/digital mixed integrated circuit that is mixed with an analog circuit section described in a cell or as an analog cell described as a circuit simulation primitive, and which can be laid out using a layout program, or a digital circuit section. After registering the circuit written in It was designed to do this.

[Effect]

In the present invention, since circuit simulation primitives are included in analog cells, the same data for circuit simulation and circuit data for layout can be used. Therefore, one analog/digital mixed LS
The layout circuit of I can be described using a unified description method.

〔Example〕

FIG. 1 shows a flowchart of one embodiment of the present invention. This embodiment is an example of a computer-aided design (CAD) system for an analog/digital mixed LSI. First, an analog circuit of an analog/digital mixed integrated circuit that has both an analog circuit section and a digital circuit section on one chip. Department?
Analog cells that can be laid out using the standard cell layout program are described, and A/D mixed description circuits that are described within the analog cells or with circuit simulation primitives are registered (step 101).

Therefore, in this embodiment, when simulating the layout circuit shown in FIG. 3, the same A/D mixed description circuit as shown in FIG. 3 is registered.

Next, the layer expansion program expands the secondary layer of the A/D mixed description circuit (step 102).
) is registered in the database 103 of logical information expanded to the cell level (step 103). The information registered in this database is expanded into cells based on the layout information 104 by the cell expansion program (steps 1 to 5), and expanded to primitives that are basic unit elements of simulation that can be simulated. Here, as mentioned above, the analog cells of the A/D mixed description circuit are described using analog primitives for the circuit simulator, so the expansion of the cells described above may result in circuit expansion that includes a mixture of analog primitives and digital primitives. be done.

Thereafter, the analog/digital separation program distinguishes and separates analog primitives and digital primitives from their identifiers, and creates circuit simulation data from the analog primitives and logic simulation data from the digital primitives (step 106). , and store them separately in the database (steps 107, 108').

Finally, a simulation is performed by the circuit simulator 109 based on the above circuit simulation data, and a simulation is performed by the logic simulator 110 based on the above logic simulation data.

In this way, according to this embodiment, the description at the time of circuit registration can include a mixture of analog circuit sections and digital circuit sections, and as a result, back annotation of wiring capacitance after layout is possible.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to describe the layout circuit of one analog/digital mixed LSI using a unified description method and register the circuit. It has certain characteristics.

[Brief explanation of drawings]

Fig. 1 is a flowchart of an embodiment of the present invention, Fig. 2 is an explanatory diagram of a conventional example, Fig. 3 is a circuit diagram of an example of a layout circuit, and Fig. 4 is an example of a conventional logic simulation description circuit. Circuit Diagram FIG. 5 is a circuit diagram of an example of a conventional circuit simulation description circuit. In the figure, 101 is an A/D mixed description circuit registration processing step;
2 is a user hierarchy expansion processing step, 105 is a cell expansion processing step, 106 is an analog/digital separation processing step, 10
9 indicates a circuit simulator, and 110 indicates a logic simulator. Patent applicant Fujitsu Co., Ltd. 1 Jti'EJ Diagram Layout [1 yen, 1 set, 1 Oka & ffi Diagram 3 Diagram

Claims (2)

[Claims] (1) To verify the design of an analog/digital mixed integrated circuit that has both an analog circuit section and a digital circuit section on one chip, a circuit simulation is performed for the analog circuit section, and a logic simulation is performed for the digital circuit section. In the simulation method, the inside of the cell is described using primitives for circuit simulation, and the analog circuit section described using analog cells that can be laid out in a layout program is mixed with the digital circuit section. (101), and after expanding the hierarchy and cells by mixing analog primitives and digital primitives (102 to 105), the analog/digital separation program separates data into circuit simulation data and logical simulation data, respectively. Perform simulation (106-110
) A simulation method for an analog/digital mixed integrated circuit. (2) The analog/digital mixed integrated circuit simulation method according to claim 1, wherein the layout program is a standard cell type layout program.