System Management has historically been a topic of concern for high-end systems. For designers of low-cost, single-board applications, “system management” often consisted of a couple of 9V battery clips, an FET, an LED, and some bailing wire. However, the proliferation of sophisticated technology into low-end systems, combined with the increasingly urgent need for power efficiency, has moved true system management issues right down into the realm of the single-boarders.
Many single board systems today are getting into big-league system management requirements with multiple power supplies in a variety of voltages, power management, thermal monitoring and management, complex power sequencing during events like startup and shutdown, and system-level clocking. These tasks often require analog monitoring and control capabilities such as identifying and responding to alert conditions. System management is also tasked with logging alarms and events, closed-loop control, and diagnostics and prognostics.
Unfortunately, most system management solutions have been created with the big-BOM mentality. $10-$30 worth of system management hardware is inconsequential in a design with two or three high-end FPGAs, a bunch of expensive memory, and assorted other exotic components and connectors. However, if you’re in the cheap board or high-volume crowd, such expensive system management solutions send you searching for alternatives. MCUs, system management ASSPs, and home-crafted solutions built from discrete analog parts all get pressed into action on a regular basis, but each has its shortcomings.
If an ASSP exists for your specific application, of course it will be cost-effective, but if you deviate from the center-line of the ASSP’s intended system, you’ll run into serious issues trying to bend an inflexible product to meet your needs. Homegrown analog solutions can stack a lot of components onto your BOM and your board, and MCUs – while highly flexible, require a lot of additional support circuitry in order to boot themselves up and manage your system.
Actel is exploiting this niche of low-cost, low-power system management with their recent announcement of system management IP and reference designs for their Fusion non-volatile, mixed-signal FPGA family. The new reference design takes about half of the smallest Fusion device, leaving copious resources available for other tasks on your board. The company estimates that, given the price of Fusion devices in volume, only about $1.20 worth of logic resources are required for the new Fusion-based system management implementation.
The Actel solution is based on the company’s previously-announced CoreABC soft microcontroller – a very compact MCU implemented in Fusion’s flash-based FPGA fabric. The MCU can be run from either Fusion’s embedded SRAM or embedded flash memory. It is capable of very fast response times (<100ns) and is designed for deterministic operation – a nice feature if you don’t want your system management tasks accidentally blocked by something like your “demo” video game or power-on sound effects.
The system management reference design (which can be downloaded for free from the Actel website) supports intelligent power management – allowing you to monitor and optimize system power on multiple supply rails – up to four voltages and three currents. It also supports a thermal monitor to track ambient system temperature. On the control side, the design has five gate drivers for functions such as power sequencing and fan control. Using these basic elements, you can code up your own system management implementation very quickly, and the resulting hardware requires fewer than 1100 FPGA “tiles” (Actel’s version of the basic FPGA logic cell).
This type of application is probably just the tip of the iceberg in terms of the things we’ll see implemented in Actel’s novel mixed-signal FPGA technology. The low-cost integration potential of these devices is huge, and an FPGA dropped on your board for a function like system management will likely, over time, start pulling in other functions as well. Indeed, if you implement system management with the smallest Fusion device, more than half of the resources on the FPGA are still sitting there waiting for you to do something interesting with them. That temptation usually leads to a little glue logic here and a little data stream conversion there and pretty soon, you’re buying a bigger FPGA because you need more space to hold all the parts of your board that you’re replacing. Of course, that’s exactly what Actel wants you to do.