The module can be powered by the B2B connector or the USB connector. If both power supplies are available, the B2B connector power supply takes precedence, disabling the USB power supply automatically.
- 1.2 V, 1 A max
- 2.5 V, 1 A max
- 3.3 V, 1 A max
The power rails are available for the FPGA and can be shared with a baseboard by the corresponding lines of the B2B connectors J4 and J5. Please note that the power consumption of the FPGA is highly dependent on the design actually loaded. So please use a tool like Xilinx Xpower to determine the expected power consumption.
Even if the provided voltages of the module are not used on the baseboard, it is recommended to bypass them to ground with 10 nF - 100 nF capacitors
B2B Connector Power Suplly
The B2B connector power supply requires a single nominal 5 V DC power supply. The power is usually supplied to the module through the 5 V contacts (5Vb2b) of the B2B connectors J5 (see Appendix). The recommended minimum supply voltage is 4 V. The maximum supply voltage is 5.5 V. The recommended maximum continuous supply current is 1.5 A.
I/O Bank Power Supply
The Spartan-3E architecture organizes I/Os into four I/O banks (see the table below).
Bank | SupplyVoltage (V) | Min(V) | Max(V) |
|---|---|---|---|
B0 | VccIO | 1.2 | 3.3 |
B1 | 2,5 | - | - |
B2 | 3,3 | - | - |
B3 | 3,3 | - | - |
I/O banks power supply
Voltage for banks B1, B2 and B3 is fixed respectively to 2,5 V, 3,3 V and 3,3 V.
Voltage VccIO for bank B0 shall span from 1.2 V to 3.3 V. VccIO can be supplied either externally or internally to the micromodule.
Spartan-3 I/Os are not 5 V tolerant. Applying more than the recommended operating voltages at any pin, results in a damaged FPGA (see Xilinx Answer AR#19146).
VccIO can be externally supplied over the B2B connector J4. If bank B0 is not used, then VccIO can be left open.
If VccIO is not externally supplied, it can be internally supplied by one of the internal power rails of 2.5 V and 3.3 V. This is possible by short-circuiting one of the two pad pairs placed on the right of connector J4 at the top right corner of the bottom side of the micromodule.
Two suitable ways of shirt-circuiting the paid pair are by means of
- a zero-ohm 0603 (1608 metric) chip resistor or
- a solder blob.
This figure shows how to short-circuit VccIO to internal 3.3 V power rail.
R102 pad pair (blue highlight) for 3.3 V internal supply.
This figure shows how to short-circuit VccIO to internal 2.5 V power rail.
R103 pad pair (blue highlight) for 2.5 V internal supply.
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