New-Tech Europe | December 2016 | Digital Edition

Power Architecture #3: Housekeeping using Control PLD with Microcontroller-based Power Management through a PMBus

voltages instead of the Power Good signal) requires adding an A/D converter, increases cost & complexity to the board. • Requires a board-level engineer (with digital expertise) to implement, someone who, in many cases, is not be a power supply expert. In this split-function architecture, a Power Manager IC is responsible for monitoring and sequencing the board's DC-DC converters (Fig.3). Because it directly monitors the supply's voltage the Power Monitor can also perform trimming and margining. The Control PLD uses the supplies' Power Good status lines to generate the necessary control, status and housekeeping signals. For these designs, the Power Manager functionality is typically defined using GUI-based configuration tools while the Control PLD logic is defined using VHDL or Verilog. Pros: • Lower Control PLD I/O count because the Enable function is handled by the Power Manager. • Lower board congestion means a simpler layout and fewer board layers. • By directly monitoring the supply voltages, the Power Monitor IC can get a more accurate picture of overall system health and enable higher system reliability. Cons: • Power manager ICs increase BOM cost – especially if multiple devices are required. • This architecture can provide Event-Based response but it adds to design complexity if more than one Power Manager is employed. • Scaling sequencing to more complex designs can be difficult – especially if it involves partitioning functionality across multiple Power Manager ICs. • Since the design process is

Fig.4: A Hardware Management system implemented using a Control PLD and an MCU

Power Architecture #4: Power Management and Housekeeping using a Control PLD with on-chip ADC

Fig.5: A Hardware Management system implemented using a Control PLD with an on-chip ADC

complex designs begin to suffer from high Control PLD I/O count and board congestion. • Reduced reliability because the Power Good fault detection is

inaccurate (typically 8% to 20% error) and cannot monitor trends in supply voltage. • Adding Telemetry (monitoring the actual supply

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