Powering the XEM8350

The XEM8350 requires a clean, filtered, DC supply within the range of 5 V to 16 V.  This supply may be delivered through the DC power connector (rated to 5 A max current) or through the mezzanine connectors (rated to 16 A max current).

The XEM8350 power distribution system is quite complex, with several supplies designed to provide suitable, efficient power for several systems and modules. A schematic diagram of the system follows, with input (+VDC) shown to the left and accessible supply rails shown to the right.

Supply Heat Dissipation (IMPORTANT!!)

Due to the limited area available on the small form-factor of the XEM8350 and the density of logic provided, heat dissipation may be a concern.  This depends entirely on the end application and cannot be predicted in advance by Opal Kelly.  Heat sinks may be required on any of the devices on the XEM8350.  Of primary focus should be the FPGA (U15) and SDRAM (U24, U25, U26, U27, U28).  Although the switching supplies are high-efficiency, they are very compact and consume a small amount of PCB area for the current they can provide.

If you plan to put the XEM8350 in an enclosure, be sure to consider heat dissipation in your design.

Power Supply

The XEM8350 is designed to be operated from a single 5-16-volt power source supplied through the DC power jack on the device.  This provides power for the several high-efficiency switching regulators on-board to provide multiple DC voltages for various components on the device as well as three adjustable supplies for the peripheral.

DC Power Connector

The DC power connector on the XEM8350 is part number PJ-102AH from CUI, Inc.  It is a standard “canon-style” 2.1mm / 5.5mm jack.  The outer ring is connected to DGND.  The center pin is connected to +VDC.

The PJ-102AH jack is rated for 5 A maximum continuous current. Applications requiring higher current must use the mezzanine connectors for providing power to the system (rated for a maximum of 16 A).

Power Budget

The table below can help you determine your power budget for each supply rail on the XEM8350.  All values are highly dependent on the application, speed, usage, and so on.  Entries we have made are based on typical values presented in component datasheets or approximations based on Xilinx power estimator results.  Shaded boxes represent unconnected rails to a particular component.  Empty boxes represent data that the user must provide based on power estimates.

The user may also need to adjust parameters we have already estimated (such as FPGA Vcco values) where appropriate. All values are shown in milliwatts (mW). Note that this table does not include the two supplies dedicated to the GTH transceivers. These are independent and can be computed separately for power budget based on their assigned function.

COMPONENT(S)0.95 V1.0 V1.2 V1.2 V1.8 V3.3 VVIO_MC1VIO_MC2
Programmable clock150
FX3 USB Host Interface385
DDR4 VTT Termination300
Misc System Functions 2970
FPGA VCCO64 + VCCO65 (USB Host Interface)25
FPGA VCCO66 + VCCO67 + VCCO68 (DDR4)250
Total (mW) 6,8701,8102,84022103,300
Available (mW)38,00080002,4004,8007,2006,6002000 mA
2000 mA
1.8-3.3 V

Example XEM8350-KU060 FPGA Power Consumption

XPower Estimator version 14.3 was used to compute the following power estimates for the Vccint supply. These are simply estimates; your design requirements may vary considerably. The numbers below indicate approximately 80% utilization.

Clock200 MHz GCLK, 400,000 fanout1,132
Clock300 MHz GCLK, 140,000 fanout954
Clock200 MHz SR, 50,000 fanout258
Logic200 MHz, 150,000 logic LUTs, 50,000 shift registers, 50,000 distributed RAMs, 400,000 registers2,766
Logic300 MHz, 50,000 logic LUTs, 140,000 registers487
Logic667 MHz (DDR4), 8000 logic LUTs155
BRAM18-bit, 200 MHz, 1000 block RAMs, 50% toggle rate2,636
BRAM36-bit, 300 MHz, 500 block RAMs, 50% toggle rate4,664
DSP500 MHz, 2200 slices, 12.5% toggle rate2,991
GTH32 channels, 16.3 Gb/s1,343
Misc.DCM, PLL, VCCINT_IO, etc.500
Total17,886 mW
Available38,000 mW

Heat Sink

FANSINK-40X40 Availability

As of 2022-03-10, the FANSINK-40X40 is no longer available due to component obsolescence. Opal Kelly is working to procure an alternative solution and will update here when this is available.

Please see below for additional options.

The device has been fitted with two heat sink anchors, proximate to the FPGA for mounting a passive or active heat sink. The following heat sink has been tested with the XEM8350.

Opal Kelly IncorporatedFANSINK-40X40Active heatsink with DC fan

The active heat sink above includes a small fan which connects to the fan controller on-board for manual or automatic fan speed control. The fan is powered directly by the input supply to the XEM8350. The fan is specified for a nominal operating voltage of 6-13.8 VDC. Supply voltages outside of this range might be possible, but could lead to fan startup and performance issues under certain conditions. The fan is powered directly by the input supply, and therefore the maximum fan RPM is related to the external supply voltage. Designs with high FPGA on-chip power consumption must take this into account when selecting an operating voltage and heat sink.

The FANSINK-40X40 is available for purchase directly from Opal Kelly.

Heat Sink Dimensions

DIY Fansink Solution

The following components may be used to craft a suitable replacement for the FANSINK-40X40:

ComponentDigi-Key P/nDescription
Aavid 375024B60024GMouser 532-375024B60024Heatsink with anchor arms
CUI CFM-3510CF-190-277Mouser 179-CFM3510CF190277
Digi-Key 2223-CFM-3510CF-190-277-ND
McMaster-Carr 92196A235McMaster-Carr 92196A235Mounting bolt
Molex 510210200Mouser 538-51021-0200
Digi-Key WM1720-ND
Power connector
Molex 500798xxxDigi-Key WM25388CT-NDCrimp terminals
Molex 500798xxxDigi-Key WM15250-NDPre-crimped cable assemblies