Digilent NetFPGA-SUME Manual de referência - Página 4

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NetFPGA-SUME™ Reference Manual

pins 15 and 16 of the main 20 pin connector of the standard ATX power supply must be shorted together, as

shown in Figure 3. If these pins aren't shorted together then the power supply will not turn on.

Figure 3. Pin 15 and 16 of Standard ATX power supply shorted together.

According to Revision 1.0 of the PCI Express 225 W/300 W High Power Card Electromechanical Specification, the

2x3 pin plug is guaranteed to deliver up to 75 watts of power, while the 2x4 pin plug is guaranteed to deliver up to

150 watts of power. While the board may be powered by either a 2x3 pin or a 2x4 pin PCI Express Auxiliary Power

plug, due to the potential for high power consumption, Digilent recommends using a 2x4 pin plug to provide power

whenever possible.

Figure 4. Power connector (J14).

Figure 4 describes pin-out of the power connector (header J14) when a 2x4 pin or a 2x3 pin plug is used. The

Sense0 and Sense1 pins are to be connected to GND when power is present, and left floating otherwise. Since the

2x3 pin plug does not include a Sense1 pin, it's possible to determine what type of plug is present, and thus how

much power can be consumed.

The FPGA logic can determine whether or not a 2x4 pin is present by enabling an internal pull-up on pin AW42 and

then checking the state of that pin. If logic '0' is seen on AW42, then a 2x4 plug is connected and up to 150 watts of

power can be drawn. If logic '1' is on AW42, then a 2x3 plug is connected, and the board's power consumption

should be limited to 75 watts or less.

2.2

Power Supply Topology

The high performance Virtex-7 FPGA, QDRII+ memories, and DDR3 memories featured on the NetFPGA-SUME

require several different supply voltages (supply rails) in order to function. These components also require that the

supply rails are sequenced on and off in a particular order. Table 1 lists the various supply rails, their nominal

voltages, and rated output currents.

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