Powering the XEM8305

The XEM8305 requires a clean, filtered, DC supply within the range of 5V to 15V. The recommended supply voltage is 12V. This supply must be delivered through the expansion connector (rated to 4A max current).

Supply Heat Dissipation (IMPORTANT!!)

Due to the limited area available on the small form-factor of the XEM8305 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 XEM8305. Of primary focus should be the FPGA (U1), SDRAM (U4, U5) and MGT regulators (U8, U9). 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 XEM8305 in an enclosure, be sure to consider heat dissipation in your design.

FPGA heatsink information is provided on the Specifications Page

Power Supply

The XEM8305 is designed to be operated from a single power supply of 5V to 15V supplied through the expansion connector 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.

A block diagram of the power distribution system is shown below.

Expansion Connector Power

Power for the XEM8305 is connected through the expansion connector MC1. A supply voltage from 5V to 15V must be provided. The suggested nominal supply voltage is 12V. The power input on the expansion connector is rated for up to 4A.

Find the pin connections in the Pins sheet.

Input Power Protections

The XEM8305 includes an over-voltage protection circuit which disconnects the input supply from the on-board circuitry when the input is higher than 15V (28 V absolute maximum). It is also prevented from powering on when the input supply is below 4.5V. The input current is limited to 5A, and it is protected from a reverse polarity voltage connection.

External I/O Voltage

The XEM8305 requires external power input for the VCCO I/O rails. The VCCO I/O rails are connected directly to the expansion connector without any onboard regulators. Power must be supplied through the expansion connectors at the desired I/O voltage.

The VCCO I/O rails should be powered only after the rest of the FPGA power rails are up and good. The XEM8305_PG signal available on MC1 can be used to sequence the power on of external VCCO I/O regulators. FPGA power is good when this signal is high with a 1.8V signal level.

The XEM8305 provides a 1.8V power output on the expansion connector MC2. This voltage falls in the valid range for all VCCO I/O rails and can be used to power the rails if externally connected to the VCCO I/O expansion connector pins on the carrier board. This rail already provides the correct power sequencing for the VCCO I/O inputs.

Find the pin connections in the Pins sheet.

IMPORTANT: Care must be taken to supply a VCCO I/O voltage in the valid range for the connected bank.

VCCO RailBank TypeVoltage Range
VCCO_64HP0.95v – 1.90v
VCCO_84HD1.14v – 3.40v
VCCO_85HD1.14v – 3.40v
VCCO_86HD1.14v – 3.40v

LED Indicators

The XEM8305 includes three LED indicators for power status.

PWR IN (D8)+VDCIN present and valid
PWR GOOD (D9)All on-board power supplies active and within expected range
(Does not include external VCCO rails)
FAULT (D11)Indicates an invalid input voltage or overcurrent.

Power Budget

The table below can help you determine your power budget for each supply rail on the XEM8305. 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 AMD power estimator results. 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 where appropriate. All values are shown in milliwatts (mW) unless otherwise specified.

COMPONENT(S)0.85 V1.2 V1.8 V2.5 V
Clock oscillators120
FX3 USB host interface648
DDR4 VTT termination231
Total (mW)14418,71271
Available (mW)10,200N/A10,800N/A

Example FPGA Power Consumption

AMD Power Estimator (XPE) version 2022.2.1 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.

Clock400 MHz GCLK, 124,560 fanout627
Clock500 MHz GCLK, 15,977 fanout302
Clock500 MHz (PCIe Gen4) GCLK, 7,208 fanout142
Logic400 MHz, 62,400 logic LUTs, 124,000 registers1,848
Logic500 MHz, 8,045 logic LUTs, 15,977 registers298
Logic500 MHz (PCIe Gen4), 3,354 logic LUTs, 7,208 registers129
BRAM36-bit, 500 MHz, 80 block RAMs, 12.5% toggle rate177
BRAM36-bit (PCIe Gen4), 500 MHz, 22 block RAMs, 12.5% toggle rate45
DSP600 MHz, 460 slices, 12.5% toggle rate1,132
GTH12 channels, 16 Gb/s1242
Misc.DCM, PLL, VCCINT_IO, etc.100
Total5,942 mW
Available10,200 mW