The LFE5U-45F-8BG381C combines a 44K-LUT ECP5 fabric, 1,944 kb of embedded block memory and 72 dedicated 18 × 18 multipliers. It provides 203 user I/O in the BG381 package. This is the logic-only LFE5U device, so a design that requires an embedded multi-gigabit transceiver needs a different device choice and a separate board review.
Technical reference updated October 19, 2026. The figures are manufacturer specifications; design examples are calculations with stated assumptions.
Ordering and resource reference
The full LFE5U-45F-8BG381C code appears in the commercial ordering table. LFE5U identifies the device without SERDES; 45F selects the density; -8 is the fastest of the listed speed grades; BG381 is the lead-free, 381-ball caBGA option; and C indicates commercial junction-temperature operation. Do not order from the shortened “ECP5-45F” family label when the prefix, speed, package and grade matter.
| Logic fabric | 44K LUTs in the manufacturer selection table |
|---|---|
| sysMEM block RAM | 108 × 18 kb blocks; 1,944 kb |
| Distributed RAM | 351 kb, separate from block RAM |
| Dedicated multipliers | 72 units of 18 × 18 bits |
| PLLs / DLLs | 4 / 4 |
| User I/O in BG381 | 203 |
| Hard SERDES channels | 0 |
| Mechanical package | 381-ball caBGA, 17 × 17 mm, 0.8 mm pitch |
| Commercial junction range | 0°C to +85°C |
The family data sheet distinguishes multiplier resources from the internal sysDSP slice architecture. Counting 72 multipliers as 72 slices and then multiplying that count again would overstate arithmetic capacity. Likewise, EBR is not the same resource as distributed LUT RAM.
Translate a DSP requirement into a fit question
Consider a hypothetical real-valued FIR stage with 64 taps, signed operands no wider than 18 bits and one dedicated multiplier per tap. A fully parallel multiplication stage would consume 64 of the listed 72 multiplier resources, leaving eight before any other arithmetic functions. This simple count excludes adders, accumulator width, rounding, saturation, coefficient storage, routing and scheduling. It does not establish a sample rate or a working implementation.
If wider operands require multiple primitives, or complex multiplication uses more than one real multiply, redo the allocation from the chosen architecture. Alternatively, sharing a multiplier over several cycles changes the clock and latency requirements. Synthesize the actual HDL for this exact device and inspect the mapping report, then verify clock constraints and timing after placement and routing. The -8 grade describes silicon timing tables; it does not guarantee the requested system frequency.
Pinout, banks and external interfaces
Import the ECP5U-45 pinout using the BG381 column and reconcile it with the schematic symbol. The 203 user I/O figure is a package resource total. Boot signals, clocks, references and shared functions can reduce the pins available to the chosen application. Write down the intended VCCIO and I/O standard for every bank before routing a wide parallel bus or DDR interface.
PCIe, SGMII and CPRI electrical links cannot be assigned to nonexistent LFE5U SERDES pins. Parallel LVDS and a soft MIPI interface are different engineering cases and require their own electrical, IP and timing checks. Neither a general list of ECP5 interfaces nor the availability of a protocol IP core proves that this exact FPGA, package and board can connect directly to a particular endpoint.
Supply rails and first configuration
Budget VCC at 1.1 V nominal within 1.045–1.155 V, and VCCAUX at 2.5 V nominal within 2.375–2.625 V. Select bank voltages for the actual I/O standards and check recommended conditions, ramp rates and power-on-reset levels. A 3.3 V I/O bank does not make VCCAUX a 3.3 V supply. Use the hardware checklist's power and configuration sections when choosing filtering, bypassing and mode connections.
The configuration SRAM loses its contents without power. Plan a compatible SPI-flash boot arrangement or a supported host-driven configuration path, and keep JTAG access for diagnosis. Confirm how external peripherals behave while the FPGA is unconfigured. In board acceptance, inspect rails and configuration status before enabling an application interface; then check the boot process after a full power cycle as well as a debugger load. These are suggested verification steps, not reported bench results.
Density changes and procurement decisions
The BG381 members do not even expose identical user-I/O totals: 25F has 197, this 45F has 203 and 85F has 205. The official caBGA381 migration file is therefore an essential input to a replacement review. Compare functions on every used ball, device constraints, power demand and temperature limits. Compile for the replacement and validate the board; sharing the package outline is insufficient evidence for a drop-in claim.
Keep the intended package and commercial grade in any RFQ. Request current availability and product-status evidence for the exact code, alongside lot identification and assembly handling information. Price, delivery and compliance depend on the offered supply and documents. This reference makes no commitment about those commercial conditions.
Manufacturer documents
- ECP5 and ECP5-5G Family Data Sheet, FPGA-DS-02012-3.4, September 2025: Table 1.1, recommended operating conditions, configuration, pin summaries and commercial ordering tables.
- ECP5 and ECP5-5G Hardware Checklist, FPGA-TN-02038-2.1, September 2025: power, configuration connections and schematic checks.
- Device-specific ECP5U pinout; select the 381-ball package column.
- ECP5 documentation directory, including the caBGA381 migration file and current configuration and software resources.