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Application Note AC318
20 – Power-Up/-Down Behavior of ProASIC3/E
Devices
Introduction
Actel ProASIC3/E devices are flash-based FPGAs manufactured on a 0.13 m process node.
ProASIC3/E FPGAs offer a single-chip, reprogrammable solution and support Level 0 live at power-
up (LAPU) due to their nonvolatile architecture.
Three main voltage pins are used by ProASIC3/E devices during normal operation:1
VCC: Voltage supply to the FPGA core
VCCIBx: Supply voltage to the bank's I/O output buffers and I/O logic. Bx is the I/O bank
number.
VMVx: Quiet supply voltage to the input buffers of each I/O bank. x is the bank number.
The I/O bank VMV pin must be tied to the VCCI pin of the same bank. Therefore, the supplies that
need to be powered up/down during normal operation are VCC and VCCI. These power supplies can
be powered up/down in any sequence during normal operation of ProASIC3/E FPGAs. During
power-up, I/Os in each bank will remain tristated until the last supply (being either VCCIBx or VCC)
reaches its functional activation voltage. Similarly, during power-down, I/Os of each bank are
tristated once the first supply reaches its brownout deactivation voltage.
ProASIC3/E devices exhibit very low transient current on each power supply during power-up. The
peak value of the transient current depends on the device size, temperature, voltage levels, and
power-up sequence.
ProASIC3/E device inputs can be driven while the device is not powered. The driven I/Os do not pull
up power planes, and the current draw is limited to very small leakage current. Therefore,
ProASIC3/E FPGAs are suitable for applications in which cold-sparing is required. All ProASIC3E
devices and the A3P030 device in the ProASIC3 family are also designed to be compatible with hot-
swap applications.2
Transient Current
The source of transient current, also known as inrush current, varies depending on the FPGA
technology. Due to their volatile technology, the internal registers in SRAM FPGAs must be
initialized before configuration can start. This initialization is the source of significant inrush
current in SRAM FPGAs during power-up. Due to the nonvolatile nature of flash technology,
ProASIC3/E devices do not require any initialization at power-up, and there is very little or no
crossbar current through PMOS and NMOS devices. Therefore, the transient current at power-up is
consumption by SRAM FPGAs vs. Actel's antifuse and flash FPGAs.
1.
For more information on ProASIC3/E device voltage supplies, refer to the appropriate datasheet located at
2.
For more details on the levels of hot-swap compatibility in ProASCI3/E devices, refer to the "Hot-Swap Support"
section in the I/O Structures chapter of the handbook for the device you are using.