Trusting the Power Numbers

With claims in cyberspace about "zero-power" CPLDs and FPGAs, and "optimized for low power" with standby current as low as 35 mW, how can you trust anything you hear about power in programmable logic?

Actel doesn't expect you to just trust us. We want you to prove it to yourself and then tell all your friends. If you read through the other pages in eZone, you may get the point that Actel is serious about delivering honest, good technology to meet your needs. When it comes to power, there is no point in our convincing you we have low power, only to let you find out later that we didn't really have it. So we have made every effort to provide tools to help you predict power. We give you multiple boards that don't calculate the power for you, but instead let you attach a multimeter and measure it for yourself. Measure not just core power, but isolated I/O bank power. Let us explain what options are available.

The Power Calculator — Excel Spreadsheet

Enter the parameters of your design and then review power consumption, in Flash*Freeze mode, at different operating frequencies, and at different I/O voltages. And notice, when you change drive strengths, the power number changes correctly. If you've ever looked closely at, say, a competitor's power calculator, you might not find it quite so responsive. Using Excel allows you to see the calculations being made and save your analysis, unlike web-based calculators.

Power-Driven Layout

In the area of low-power design, much discussion takes place about such things as optimizing clock networks to reduce switching and power. Actel's new power-driven layout will move blocks together onto single clock trees to minimize switching current throughout the device, in addition to using other optimization techniques to reduce power consumption by as much as 30% in a suite of designs tested.

Power Profiling

Power profiling may not be a standardized technique, but it is a requirement of low power and especially battery-operated designs. When you design a low-power application, knowing that active power is 20 mW is not enough. You need to know standby power, low-frequency power options, and how much time you might spend in each mode. What does this do to your power budget and power supply design? In the Actel SmartPower analysis tool, you can define different modes of operation and enter the percent of time spent in each mode to get a clear picture of your power consumption and battery life through all modes of the product.

Cycle-Accurate Power Reports for Hazard Analysis

With an accurate testbench, ModelSim® can export switching data for your design. This information, loaded to SmartPower, can produce an average power consumption value. Other power analysis tools may do this, but the latest version of SmartPower now uses the cycle-accurate data created by the testbench. The new Activity and Hazards Power Reports enable you to quickly identify gates and nets of the design that consume power because of spurious transitions, allowing you to identify areas of your design with the potential to reduce power consumption.