Specifications

Nexys3 Reference Manual
Doc: 502-182 page 8 of 22
Power
Jack
Battery
Connector
Power Select
Jumper JP1
VU
1.8V
2.5V
1.2V
3.3V
IC13: LTC3633
EN
Power
Switch
Power On
LED (LD8)
IC15: LTC3619
ON
OFF
J11
Power GoodEN
3A
3A
400mA
800mA
USB port
Micro-USB
Power GoodEN
VUEXP
JP4
The Nexys3 power supplies are enabled (or turned on) by a logic-level Power switch (SW8). A power-
good LED (LD8), driven by the wired-OR of the “power good” outputs on the supplies, indicates that
all supplies are operating within 10% of nominal.
The VU output of the main power jumper (JP1) is available to the VHDC expansion connector if
jumper JP4 is loaded. Care must be taken to ensure the VUEXP delivered to any attached expansion
board is the correct voltage – since VU is driven directly from an attached supply, this means a supply
of the proper voltage must be used (e.g., 5V).
Memory
The Nexys3 board contains three external memories, all from Micron: a 128Mbit Cellular RAM
(pseudo-static DRAM); a 128Mbit parallel non-volatile PCM (phase-change memory); and a 128Mbit
serial PCM device. The Cellular RAM and parallel PCM device share a common bus, and the serial
PCM is on a dedicated quad-mode (x4) SPI bus. The non-volatile PCM memories are byte and bit
alterable without requiring a block erase, so they are faster and more versatile than conventional
Flash in most applications.
The 16Mbyte Cellular RAM (Micron part number M45W8MW16) has a 16-bit bus that supports 8 or 16
bit data access. It can operate as a typical asynchronous SRAM with read and write cycle times of
70ns, or as a synchronous memory with an 80MHz bus. When operated as an asynchronous SRAM,
the Cellular RAM automatically refreshes its internal DRAM arrays, allowing for a simplified memory
Nexys3 Power Supplies
Supply
Circuits
Device
Amps (max/typ)
3.3V
FPGA I/O, USB ports, Clocks, ROM & RAM I/O, Ethernet
IC13: LTC3633
3A / 200mA
2.5V
Optional voltage for Bank0 and VHDC connector
IC14: LTC3619
800mA / 0mA
1.2V
FPGA Core
IC13: LTC3633
3A / 0.2 to 1.0A
1.8V
RAM and ROM core
IC14: LTC3619
400mA / 0.1 to 0.3A