Employ dynamic power reduction in an ASIC

Incorporate power-saving methods at multiple levels in application-specific IP.

By Somnath Viswanath, inSilica Inc
(09/14/07, 01:30:00 AM EDT), Embedded Systems Design

Increasing battery life without compromising performance and functionality is a prime concern for the handheld market. The form-factor and economics of this market also demand an ever increasing level of integration for these devices. Each generation of handheld devices sets more aggressive battery-life goals, making power reduction an important consideration for the system designer.

To achieve this objective, system architects must incorporate power-saving methods into all aspects of device implementation. Monitoring and analyzing patterns of application use reveals opportunities to optimize power. These opportunities should be recorded in a power-optimization specification that guides the selection of power-reduction techniques for each component in the system. Techniques to lower power can be applied to both software and hardware components.

A handheld device consists of a display unit, keyboard, and audio I/O, all of which are controlled by a system-on-chip (SoC) and associated peripheral chips. Power is supplied by a rechargeable battery. A typical SoC consists of two kinds of intellectual property (IP) blocks:

• Standard third-party IP blocks (for example, an embedded processor)
• Customer-specific IP (CS-IP)

This CS-IP is the "secret sauce" that differentiates the SoC in the product segment. The standard third-party IP blocks are designed by IP vendors using mature design methods. Because these blocks are intended for integration and reuse in multiple designs, power optimizations are built into their implementation. The extent of these optimizations also help differentiate an otherwise standard building block.

When your team hands off your SoC design to the ASIC designer, you challenge the ASIC designer to meet power-reduction targets by implementing multiple power-saving techniques to the CS-IP blocks. A combination of time-to-market pressure and functional integration requirements conspire to make the ASIC designer rely heavily on proven IP to implement an SoC for the handheld market. Product differentiation is achieved by integrating standard third-party IP with CS-IP to compete in an increasingly crowded and converged handheld device market. The proprietary CS-IP is designed by IP groups whose primary focus is on functionality rather than power.

Hence, an ASIC designer integrating a CS-IP block doesn't have the requisite knowledge of its micro-architecture nor details of its verification environment. Moreover, an ASIC designer working for an ASIC vendor that's integrating the SoC is often supplied the CS-IP as a hard-macro with an encrypted simulation model, further limiting the options to modify its implementation.

In spite of these challenges, an ASIC designer can use several techniques to reduce dynamic power consumption of CS-IP blocks in an SoC. Some of these techniques don't require extensive modifications to the CS-IP, which is particularly advantageous for those CS-IP that are supplied in a format that precludes synthesis or remapping of gates.

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