The Company
ST Microelectronics is a global independent semiconductor company that designs, develops, manufactures and markets a broad range of semiconductor integrated circuits (ICs) and discrete devices used in a wide variety of microelectronic applications, including telecommunications systems, computer systems, consumer products, automotive products and industrial automation and control systems.
ST's Set Top Box Division (STB) primarily produces chips for digital demodulation for cable, satellite and terrestrial set-top box applications.
The Challenge
ST is the first company in the world to develop a single chip that integrates an RF tuner, a demodulator and channel decoder for digital satellite applications. Combining both digital and analog subcircuits in one integrated circuit is a challenging concept. The project, an integration of the Zero-IF tuner, typically a separate RF device, with the demodulator, typically a high performance digital device, on a standard 0.18µm CMOS process challenged ST at two key levels:
- At the simulation level: ST needed to simulate the complete data path to validate the feasibility of the chip before it was manufactured.
- At the test level: Once the chip was produced, stringent testing was needed in both RF and digital fields.
The Solution
Agilent's Advanced Design System (ADS) electronic design automation (EDA) software, which can simulate the entire communications signal path within a single, integrated environment, offered ST Microelectronics a big advantage. By using ADS, ST was able - for the first time - to run a complete simulation at system level of the entire signal path, including the modulator, the tuner and the demodulator, from input MPEG to output MPEG.
For testing of the circuit, ST worked with Agilent's test and measurement group to develop a special RF option for new system-on-a-chip (SOC) tester. This allowed ST to test on a single platform both the tuner section and the digital demodulation of the chip.
The Result
ST created a complete simulation reference that included transistor level effects at the system level. "ADS was a big advantage for us because we were able to test out different demodulation architectures like the gain control loops of the IC, redefine the partitioning between the analog and digital blocks, and see the effects at the system level", said Pierre Dautriche, R&D Analog Group Manager.
Before final tape out, the co-simulation capability in ADS allowed ST to verify the design and ensured that the RF, analog and digital subcircuits worked together properly. The simulation proved that the two types of circuits could be mixed.
The ability to simulate the entire circuit prior to production saved both time and money. "Without the ADS simulation capability , this complex chip would have been built and then tested - which is an expensive and time-consuming process if the design doesn't work", said Dautriche. "Simulation with ADS helped guarantee that the design was valid and feasible, resulting in a shorter design and production time, so the IC could be introduced earlier".
Once the chip was produced, ST described the use of a special RF option for the Agilent SOC testers, which is used in characterization and in production, as a key success factor in the manufacturability of this chip. This allowed ST to significantly increase the fault coverage of the test program, which helped boost the quality of ST's product and reduce the number of customer returns.
ST estimates that Agilent's help saved a complete silicon manufacturing cycle, including development of a set of masks, diffusion and assembly, evaluation and characterization. This translates into at least six months of development time, plus all the costs linked to preparation for a silicon launch to the fab.
After measuring the produced chips, ST found a good correlation between simulations and real measurements, proving the reliability of Agilent's EDA software.
The Agilent platform will be used and developed for all coming RF products of the Set top box Division in the Consumer and Microcontrollers groups of ST Microelectronics.
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