By Wendy Lockhart, Actel(12/15/07, 12:30:00 PM EST) -- Embedded.com
The availability of ARM's Cortex-M1 32-bit processor and single-chip, mixed-signal FPGAs make possible the development of intelligent power control that could dramatically reduce part count, board space, and system cost while increasing reliability, flexibility, and system availability. Methods exist for rapid prototyping and implementation of the hardware and software for server-based intelligent power; these methods can also be applied to a range of energy-management applications. System considerations include development resources; tools available for development with Cortex-M1 and mixed-signal programmable system chips (PSCs); and availability of power control boards. Lowering the cost of intelligent power control requires an understanding of FPGA implementation strategies, as well as a basic understanding of designing with ARM's Cortex-M1 microprocessor and FPGA implementation tools.
As the number of functions in a system grows, power to the system is no longer an afterthought. With time-to-market pressures and the need to support more features, designers must select peripherals from a standard set of components to meet their power and cost budgets. As a result, this may mean mixing an LCD with a 2.5-V supply and a keypad with a 1.8-V supply. With many devices, the core and I/O voltage within the device will also vary. So, within a single product, the power supply may need to generate multiple voltages and possibly different sequences of the same voltage.
In portable applications, the restrictions can be even greater, requiring power management to extend battery life. Designs can therefore become quite complex, featuring multiple supplies, controlled ramp rates, power sequencing, and complex supply management where supplies are turned on and off as needed.
Intelligent power control has existed in some high-end systems as a custom implementation or more recently with standards, such as ATCA and MicroTCA. With the market now demanding smaller, portable versions of many applications, the power control must be scaled down as well, creating a need for intelligent power control that's low cost, small form factor, and low power.
Intelligent power control involves the following basic aspects:
- Generating all the required system voltages.
- Sequencing each device's power up and down to maintain system integrity and prevent issues such as latch-up, inrush current, or I/O contention.
- Supporting the ability to switch off certain devices when not needed and power them back up for seamless operation.
- Maintaining minimum functionality in standby, with the ability to wake at certain intervals or on-demand.
Implementing these functions in an application-specific standard product (ASSP) would require a standard power profile. The use of a programmable device, however, allows for adaptation to multiple system requirements. Programmable devices also allow for future system upgrades and fine tuning. A number of programmable power modules are available, but they still need to be combined with some form of brain to tell them when to turn each supply on and off.
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