Powering the XEM7310MT
The XEM7310MT requires a clean, filtered, DC supply within the range of 4.5 V to 5.5 V. This supply must be delivered through the DC power connector or the expansion connector MC1.
The XEM7310MT power distribution system includes 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 XEM7310MT 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 XEM7310MT. Of primary focus should be the FPGA (U9) and SDRAM (U11, U12). 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 XEM7310MT in an enclosure, be sure to consider heat dissipation in your design.
Power Supply
The XEM7310MT is designed to be operated from a single 5-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 the adjustable supplies for the peripheral.
DC Power Connector
The DC power connector on the XEM7310MT 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.
Powering via USB
Note: Read this section carefully before applying this technique. The XEM7310MT power consumption depends greatly on the FPGA and device configuration and could easily exceed available power from USB.
The XEM7310MT has been designed to accept power (+5 VDC only) via the USB connector with a small modification. To power from USB, you will need to install a 0 Ω resistor (0402 dimension) at location R62, located on the reverse side of the PCB under the power connector. This will connect VBUS from the USB connector to the +VDC input on the XEM7310MT.
With this resistor in place, do not apply power to the external DC power connector.
Over-/Under-Voltage Protection
An electronic fuse on the +VDC input protects the module from over-voltage, under-voltage, and thermal overload conditions. During any one of these conditions, the fuse enters a fault state. In the fault state, the FAULT LED illuminates red and all down-stream power supplies on the module are disabled.
The table below indicates the overvoltage and undervoltage thresholds. The fault state clears automatically when the +VDC input voltage is within the specified range.
| CONDITION | RISING THRESHOLD | FALLING THRESHOLD |
|---|---|---|
| Overvoltage | 5.56 V | 5.12 V |
| Undervoltage | 3.97 V | 3.69 V |
Current Overload
The fuse has an overcurrent limit of approximately 5 A. A current overload condition does not cause the fuse to enter the fault state. Instead, the fuse enters a current limit mode, dissipating power internally to keep the output current at or below the 5 A limit. If the current overload condition continues and the thermal shutdown threshold is reached, the fuse enters the fault state. An automatic retry cycle will clear the fault state when the thermal overload condition no longer exists.
Reverse Voltage
The fuse protects against a reverse voltage/current condition, but the FAULT LED does not illuminate during this condition.
Power Budget
The table below can help you determine your power budget for each supply rail on the XEM7310MT. 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).
| COMPONENT(S) | 1.0V | 1.5V | 1.8V | 3.3V |
|---|---|---|---|---|
| 200 MHz, Misc | 250 | |||
| USB | 500 | |||
| DDR3 | 730 | |||
| FPGA Vccint, Vccbram | ||||
| FPGA Vccaux | ||||
| FPGA MGTAVCC, MGTAVTT | ||||
| FPGA Vcco15,16 (DDR3), est. | 280 | |||
| FPGA Vcco14 (USB), est. | 60 | |||
| FPGA Vcco (User I/O) | ||||
| Total (mW) | ||||
| Available (mW) | 3,000 | 2,250 | 2,700 | 4,950 |
Example XEM7310MT-A200 FPGA Power Consumption
Xilinx Power Estimator version 2015.3 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.
| COMPONENT | PARAMETERS | 1.0V | 1.8V |
|---|---|---|---|
| Clock | 150 MHz GCLK, 220,000 fanout | 570 mW | |
| Logic (DFF) | 150 MHz, 220,000 DFFs | 550 mW | |
| Logic (LUT) | 150 MHz, 100,000 | 550 mW | |
| BRAM | 36-bit, 300 @ 150 MHz | 450 mW | |
| DSP | 150 MHz, 630 slices | 300 mW | |
| Misc. | DCM, PLL, etc. | 10 mW | 500 mW |
| GTP Transceiver | 4 channels, 32-bit, 3.125 Gbps | 750 mW | |
| Total | 2,430 mW | 1250 mW | |
| Available | 3,000 mW | 2,700 mW |
FPGA Bank Voltage Configuration
The table below describes the power supply configuration of the FPGA banks on the XEM7310MT. Note that the bank voltages for banks 13, 14, 15, and 16 may not be changed. VCCO_MC1 and VCCO_MC2 are connected to 3.3v by factory default. See Expansion Connectors for information on setting different voltages.
| BANK | POWER SUPPLY |
|---|---|
| 13 | 3.3v |
| 14 | 1.8v |
| 15 | 1.5v |
| 16 | 1.5v |
| 34 | VCCO_MC1 |
| 35 | VCCO_MC2 |
FPGA Power-On Sequencing with External VCCO
The Artix-7 family of devices has the following recommended power supply startup sequence:
- VCCINT/VCCBRAM
- VCCAUX
- VCCO
This sequence achieves minimum current draw and ensures I/O are tristated at power-on. For more information see the “Power-On/Off Power Supply Sequencing” section in the Artix-7 FPGA Data Sheet (DS181).
To meet this sequencing recommendation when applying external VCCO power supplies, the external system should monitor the XEM7310MT +1.8VDD supply on mezzanine connector MC1, pin 73. This on-board voltage rail powers the FPGA VCCAUX pins directly. After the +1.8VDD rail is within regulation (within ±10%, for example), the external system may apply VCCO to the module.