功率調節約束設計

　　便攜式和嵌入式產品空間已經從簡單的日子開始，整個系統的基礎設施是基于12 V模擬傳感器和5 V邏輯電平。隨著越來越多的嵌入式顯示器，新的傳感器，內存，I OS和先進的低功耗控制器的使用，大多數嵌入式系統現在需要大量的電力領域，其中可能包括0.8至1.8伏，2.3伏，2.7伏，3.3伏，5伏和12 V電源的混合物。

　　外部電源變壓器只提供一個電壓電平，所以其余必須在PCB上生成。這通常是使用多個不同的個人權力的監管機構或一個更復雜的電源管理IC（PMIC）。這些集成電路的選擇是基于電壓輸出、當前支持的水平和設計的熱操作條件。

　　Why multiple power supplies？

　　Today‘s embedded systems are often designed using multiple technologies. Most designs have a combination of components that include MOS， bipolar， MEMS， TFT-LCD， and LED technologies. As process and manufacturing scaling has progressed， the nominal operative voltage for ICs has dropped. The amount of current per transistor has also dropped; however， since there are more transistors per chip in most designs， the net current draw has not necessarily gone down. The use of mixed technology in a design is driving the need for multiple power regulators.