The XC7K325T-1FFG900C is a Kintex-7 FPGA with a large programmable logic fabric, DSP resources and GTX serial transceivers. Choosing it requires more than matching the XC7K325T device name: the -1 speed grade, FFG900 package and commercial temperature grade constrain the board and implemented design. This guide separates device resources from package connections and gives a practical worksheet for checking an existing BOM or planning a new design.
Resources and package: use the correct units
| Logic fabric | 326,080 logic cells; 50,950 slices |
|---|---|
| Block RAM | 445 blocks of 36 Kb, equivalent to 890 blocks of 18 Kb; 16,020 Kb total |
| DSP resources | 840 DSP48E1 slices |
| Clock management | 10 clock management tiles |
| FFG900 package | 900 balls; 31 × 31 mm body; 1.0 mm ball pitch |
| User I/O in FFG900 | 500 maximum: 350 HR and 150 HP |
| GTX channels in FFG900 | 16 bonded transceiver channels |
| Integrated PCIe resource | One integrated block, supporting configurations up to Gen2 x8 |
The resource and package basis is AMD DS180: 7 Series FPGAs Overview. Logic cells are a normalized capacity measure, not a count of physical LUTs. The 50,950 figure counts slices, not CLBs. A utilization report should therefore be compared with its matching resource column, rather than comparing every reported count with the headline logic-cell number.
What the -1 speed grade changes
For the -1 grade at nominal 1.0 V, DS182 Table 56 specifies an 8.0 Gb/s GTX maximum for FF/RF packages; the FB-package column is 6.6 Gb/s. Operation above 5.0 Gb/s on -1 requires the documented four-byte internal data width. The 12.5 Gb/s Kintex-7 family headline must not be assigned to this exact part. AMD DS182: Kintex-7 DC and AC Switching Characteristics.
This distinction changes interface selection. A direct single-lane 10GBASE-R interface needs a 10.3125 Gb/s line rate, which exceeds this part’s listed limit. It does not follow that every architecture carrying 10 Gb/s of aggregate traffic is impossible: multiple lanes and an appropriate external interface can produce a different solution. Specify the protocol, encoding, lane count and reference clocks before deciding whether the FPGA fits.
Keep the implementation target set to the exact ordering code. A build that routes for a faster speed grade does not establish timing closure for -1. Save the tool version, constraints, timing report and generated image together; a successful configuration or a matching device ID alone is insufficient evidence that a deployed design meets its timing requirements.
Plan I/O banks before assigning connectors
The 900-ball package does not provide 900 general-purpose signals. Power, ground and dedicated functions occupy many balls. HR and HP banks also have different voltage capabilities: HR supports standards in the 1.2–3.3 V range, whereas HP supports 1.2–1.8 V. Use AMD DS180: 7 Series FPGAs Overview and the exact pinout from AMD UG475: 7 Series Packaging and Pinout before assigning bank supplies.
Build a bank worksheet containing each signal group, required standard, voltage, clock relationship, termination and connector destination. Reserve clock-capable pins and memory-interface groups first. A connector with enough unused pins can still be incompatible if its signals require conflicting bank voltages. Review unused-pin handling and configuration-related pins at the same time, so the first configuration cycle does not create an unexpected board-level drive condition.
Interpret RAM capacity as a resource budget
The published 16,020 Kb includes the full block organization. Application payload capacity depends on width, parity/ECC usage and how buffers pack into blocks. As a conservative illustrative mapping, 128 blocks configured for 32 data bits by 1,024 words provide 128 × 32 × 1,024 / 8 = 524,288 payload bytes, or 512 KiB. This allocation consumes 128 of the 445 physical 36 Kb blocks.
Track separate allocations for capture FIFOs, coefficient storage, packet buffers and processor memories. A total byte count can hide fragmentation when many small memories require separate physical blocks. Check the implemented utilization and actual generated memory configuration rather than assuming that every nominal RAM bit becomes freely addressable application storage.
Configuration flash: capacity is only the first check
UG470 lists 91,548,896 configuration bits for XC7K325T and a recommended minimum 128 Mb configuration memory. AMD UG470: 7 Series FPGA Configuration. Dividing the listed bit count by eight gives 11,443,612 bytes per uncompressed bitstream. Two such images total 22,887,224 bytes before address alignment, headers, metadata and any other stored content. A 256 Mb device has 33,554,432 bytes of nominal capacity, so capacity alone may accommodate that example.
That arithmetic does not qualify a flash device. Verify the supported boot interface, voltage, command set, addressing behavior, configuration clock limits and the generated memory image layout. Define recovery behavior for an interrupted update, then test it on the board. Keep a known-good image and a documented recovery connection available during development.
Temperature, memory interfaces and replacement decisions
The commercial grade specifies a 0 to +85 °C junction operating range, not an ambient-temperature guarantee. Core supply is nominally 1.0 V for this -1 part; consult the complete recommended operating conditions for every rail. AMD DS182: Kintex-7 DC and AC Switching Characteristics. Estimate junction temperature and power using the actual design activity and cooling arrangement. Neither a fixed wattage nor a mandatory heatsink size can be inferred from the part number alone.
DDR interface choices depend on the selected FPGA, speed grade and design frequency. Generate and validate the exact memory configuration using AMD UG586: Memory Interface Design Rules. Do not copy a family maximum rate into a board specification or describe the programmable memory-controller solution as a general hard DDR controller.
For a proposed substitute, compare the pinout, bank voltages, transceiver placement, resources, timing and thermal conditions. A shared family or package name does not establish drop-in compatibility. Continue with the board troubleshooting guide for bring-up evidence, or the data-acquisition budget example for system sizing.
Ordering and references
For an XC7K325T-1FFG900C quotation, send the complete code, quantity, required delivery date and documentation requirements through the WWDParts RFQ list. Availability, price and delivery terms are confirmed in the written quotation. A different package, temperature grade or speed grade requires a design review before substitution.
- AMD DS180: 7 Series FPGAs Overview
- AMD DS182: Kintex-7 DC and AC Switching Characteristics
- AMD UG470: 7 Series FPGA Configuration
- AMD UG475: 7 Series Packaging and Pinout
- AMD UG586: Memory Interface Design Rules
Technical content reviewed October 13, 2026. Worked examples are design calculations with stated assumptions, not measurements or hardware qualification results.