How small can an FPGA get?

FPGAs can get surprisingly small - from massive high-performance chips down to packages smaller than a fingernail. The physical size depends on the package type, pin count, and target application.

Physical Package Sizes
Ultra-Small FPGA Packages

Real-World Size Comparisons

• iCE40 UltraPlus WLCSP: 2.15×2.55mm (smaller than a SIM card chip)
• Lattice MachXO3 QFN: 3.5×3.5mm
• Gowin GW1N QFN: 4×4mm
• Xilinx Artix-7 CSG324: 15×15mm (larger, high-performance)

Ultra-Small FPGA Families
1. Lattice Semiconductor - The Size Leader

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iCE40 UltraPlus (WLCSP):   2.15 × 2.55 mm |  ~5k LUTs
iCE40 LP/HX (QFN):         3.5 × 3.5 mm   |  ~1k-8k LUTs  
CrossLink-NX (WLCSP):      2.5 × 2.5 mm   |  ~6k LUTs
MachXO3 (QFN):             3.5 × 3.5 mm   |  ~2k-9k LUTs

2. Gowin Semiconductor

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GW1N series (QFN):         4 × 4 mm       |  ~1k-20k LUTs
LittleBee (QFN):           5 × 5 mm       |  ~1k-5k LUTs

3. Intel (Altera)

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Max 10 (UQF):              7 × 7 mm       |  ~2k-50k LUTs
Cyclone 10 LP (UBGA):      8 × 8 mm       |  ~6k-20k LUTs

4. Xilinx (AMD)

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Spartan-7 (CSG):           8 × 8 mm       |  ~6k-100k LUTs
Artix-7 (CSG):             15 × 15 mm     |  ~15k-200k LUTs

Applications for Tiny FPGAs
Wearable Electronics

• Smart watches
• Fitness trackers
• AR/VR glasses

IoT and Embedded Systems

verilog

// Example: Tiny FPGA as I²C/SPI bridge
module i2c_spi_bridge(
    input wire clk,
    inout wire sda, scl,     // I²C
    input wire mosi, cs, sck, // SPI
    output wire miso
);
// Small enough for 2×2mm package
endmodule

Mobile Devices

• Sensor aggregation
• Display interface bridging
• Power management

Medical Devices

• Hearing aids
• Portable monitors
• Implantable devices

Resource Constraints in Small FPGAs
Even the smallest FPGAs contain essential resources:

Typical iCE40 UltraPlus (2.15×2.55mm)

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Logic Cells:   5,280 LUTs
Memory:        1 Mb SPRAM + 120 Kb DPRAM
DSP:           8 16×16 multipliers
I/O:           Up to 28 pins
PLL:           1-2 clock management

Design Considerations for Small FPGAs

verilog

// Efficient coding for small FPGAs
module tiny_design(
    input wire clk,
    input wire [7:0] data_in,
    output reg [7:0] data_out
);

// Use distributed RAM instead of block RAM
(* ram_style = "distributed" *)
reg [7:0] buffer [0:15];

// Share resources when possible
always @(posedge clk) begin
    if (enable) begin
        data_out <= buffer[addr] + offset; // Combine operations
    end
end

endmodule

Development Boards for Small FPGAs
Tiny FPGA Boards

1. Lattice iCE40 UP5K Board: ~20×20mm
2. TinyFPGA Boards: ~18×30mm
3. iCEBreaker FPGA: ~40×40mm (with debugging)
4. BlackIce MX: ~35×35mm

Comparison to Microcontrollers

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ATmega328P (Arduino):   7×7mm  |  8-bit MCU
STM32F103:              7×7mm  |  32-bit ARM Cortex-M
iCE40 UP5K:             2.5×2.5mm |  5k LUT FPGA

FPGA Advantage: Parallel processing, custom hardware

Technological Trends Making FPGAs Smaller
Advanced Packaging

• WLCSP: Bare die with solder balls
• Fan-Out Wafer-Level: Even smaller than chip-scale
• 3D Stacking: Multiple dies in one package

Process Technology

• 28nm FD-SOI: Better power efficiency
• 40nm LP: Low power for small devices
• FinFET: Higher density (in larger FPGAs)

Practical Limitations
I/O Count vs Size Tradeoff

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WLCSP 2.5mm:   Max ~25-30 I/O pins
QFN 4mm:       Max ~64 I/O pins  
QFP 10mm:      Max ~144 I/O pins
BGA 15mm:      Max ~300+ I/O pins

Power Considerations

• Tiny FPGAs: 10-100mW typical
• Sleep modes: As low as 10-50μW
• Active power: Scales with utilization

Future Outlook
Near Future (2024-2026)

• 1×1mm packages for ultra-simple logic
• Heterogeneous integration with MCUs
• More specialized tiny FPGAs for specific interfaces

Application Growth Areas

• Edge AI: Tiny FPGAs for ML preprocessing
• Sensor Fusion: Multiple sensors → one tiny FPGA
• Protocol Conversion: USB, MIPI, Ethernet bridging

Summary
The smallest commercially available FPGAs are around 2×2mm in package size (Lattice iCE40 UltraPlus in WLCSP), containing thousands of logic elements while consuming minimal power. These tiny FPGAs enable hardware programmability in space-constrained applications where microcontrollers lack the parallel processing capabilities or interface flexibility.

The choice between a tiny FPGA vs microcontroller depends on your need for parallel processing, custom hardware acceleration, and interface flexibility versus software programmability and ecosystem maturity.