Cyclone 电源管脚： VCCINT：内核电压。通常与FPGA芯片所采用的工艺有关，例如130nm工艺为1.5V，90nm工艺为1.2V。 VCCIO：端口电压。一般为3.3V，还可以支持选择多种电压，如1.8V、1.5V等。  VREF：参考电压。 VCC_PLL：锁相环管脚电压，直接连VCCIO。 VCCA_PLL：锁相环模拟电压，一般通过滤波器接到VCCINT上。 GNDA_PLL：锁相环模拟地。 GNDD_PLL：锁相环数字地。 JTAG AS VCC电源 最小系统设计可参考 http://wenku.baidu.com/view/a52f7b87ec3a87c24028c421.html
数据手册中电源参数：    Each Cyclone II PLL uses separate VCC and ground pin pairs for their
analog circuitry. The anal og circuit power and ground pin for each PLL is
called VCCA_PLL < PLL number> and GNDA_ PLL< PLL number>. Connect
the VCCA power pin to a 1.2-V power supply, even if you do not use the
PLL. Isolate the power connected to VCCA from the power to the rest of
the Cyclone II device or any other digi tal device on the board. You can use
one of three different method s of isolating the VCCA pin:
■ Use separate VCCA power planes
■ Use a partitioned VCCA island within the VCCINT plane
■ Use thick VCCA traces | 
