New-Tech Europe | December 2016 | Digital Edition

DC-DC converters which have an analog control interface (APOLs). To simplify the software design, most MCU-driven power management designs employ Time-Based sequencing schemes which issue a single fixed sequence of disable signals to power down the board when a normal turn-off is requested or when a fault condition is detected. Another potential drawback of software-based power management is that it is slower to respond to fault conditions (typically 10-15 milliseconds versus the microsecond- scale response of a Control PLD). If some fault conditions require a faster response (or Event-Based sequencing), a second layer of protection may be added using the Control PLD. Implementing software-based Power Management requires both, software for the MCU and a Control PLD design, written in either VHDL or Verilog. Pros: • Designs are easily scalable (for time-based sequencing only). • Abundant software development tools make MCU-based solutions faster and easier to debug. • Designs can be quickly modified using firmware updates. • Simpler PCB designs - routing congestion reduced around DPOLs Cons: • More expensive BOM • Difficult to scale if Event Based sequencing is required. • Multiple design tools required (Verilog/VHDL + Software) • Mix of APOL & DPOL requires a hybrid control solution which has several drawbacks: o It cannot be simulated easily. o Hardware management functions can only be tested in a prototype board environment. o Complexity increases system

Fig.6: The L-ASC10 remote sensing element.

Power Architecture #5: Power Management and Housekeeping performed by a Control PLD with L-ASC10 (ASC) providing Distributed Voltage Sensing & control

Fig.7: - A Hardware Management system implemented using a distributed architecture

spread across multiple tools (GUI + VHDL/Verilog), it may require multiple engineers and increase design risk. Figure 4 illustrates an architecture which uses a microcontroller (MCU) to perform the sequencing of digitally-controlled point of

load (DPOL) supplies. The MCU manages the DPOLs using the Power Management Bus (PMBus), a twowire communications protocol based on the I²C bus. This leaves the Control PLD responsible for supporting the board's housekeeping functions as well as controlling any point-of-load

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