The XC3S4000-4FG900C is a high-density, commercial-grade Field Programmable Gate Array (FPGA) from AMD Xilinx’s Spartan-3 family. Designed for cost-sensitive, high-volume applications, this device delivers 4 million system gates in a fine-pitch 900-ball BGA package, making it an ideal solution for engineers who need powerful logic density without the premium cost of higher-end FPGA families. Whether you are developing embedded systems, digital signal processing pipelines, or communications hardware, the XC3S4000-4FG900C offers the performance and flexibility demanded by modern designs.

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What Is the XC3S4000-4FG900C?

The XC3S4000-4FG900C belongs to the Xilinx FPGA Spartan-3 generation — one of the most widely deployed FPGA families in history. The part number breaks down as follows:

• XC3S4000 – Spartan-3 series with 4,000K system gates
• -4 – Commercial speed grade (slower propagation delay ceiling; suitable for most non-speed-critical designs)
• FG900 – Fine-pitch Ball Grid Array (FBGA), 900 balls
• C – Commercial temperature range (0°C to +85°C)

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Key Features of the XC3S4000-4FG900C FPGA

• 4,000,000 system gates — substantial logic capacity for complex control and data path designs
• 84,672 logic cells organized in a regular array of Configurable Logic Blocks (CLBs)
• 96 dedicated 18Kb block RAMs providing 1,728 Kbits of on-chip memory
• 96 dedicated multipliers (18×18-bit) for high-throughput DSP applications
• 4 Digital Clock Managers (DCMs) for precise clock synthesis, deskewing, and phase shifting
• Up to 622 user I/Os supporting a wide range of I/O standards
• FG900 package — 900-ball FBGA, 31×31 mm body with 1.0 mm pitch
• 1.2V core voltage with 3.3V, 2.5V, 1.8V, and 1.5V I/O bank support
• Commercial temperature range: 0°C to +85°C
• Manufactured on 90nm process technology

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XC3S4000-4FG900C Technical Specifications

General Parameters

Logic Resources

I/O Characteristics

Supported I/O Standards

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XC3S4000-4FG900C Ordering Information

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Spartan-3 Family Comparison: XC3S4000 vs Similar Devices

The XC3S4000 sits near the top of the Spartan-3 family, offering the second-highest gate count while remaining significantly more affordable than Virtex-series devices.

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Package Information: FG900 (FBGA-900)

The FG900 package is a Fine-Pitch Ball Grid Array with 900 solder balls arranged in a 30×30 grid matrix. Key physical characteristics are listed below.

Designers working with this package should follow Xilinx BGA PCB design guidelines, including appropriate via-in-pad or dog-bone fanout strategies, controlled impedance power and ground planes, and careful decoupling capacitor placement to maintain signal integrity.

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Digital Clock Manager (DCM) Capabilities

The XC3S4000-4FG900C includes 4 Digital Clock Managers, which provide:

• Clock deskewing to eliminate board and distribution delays
• Frequency synthesis with selectable multiplication (M) and division (D) factors
• Phase shifting in fixed or variable (fine-grain) increments
• Clock mirroring for 0°, 90°, 180°, and 270° outputs simultaneously
• DLL (Delay-Locked Loop) based clocking without VCO jitter

This makes the device well suited for multi-clock-domain designs, DDR memory interfaces, and high-speed serial applications.

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Block RAM Architecture

Each of the 96 block RAMs in the XC3S4000-4FG900C is a true dual-port 18 Kbit SRAM, configurable as:

Two adjacent 18Kb BRAMs can be combined to form a single 36Kb true dual-port RAM, offering up to 512 × 72-bit configurations. The total available block RAM of 1,728 Kbits (216 KB) supports demanding on-chip buffer, FIFO, and lookup table requirements.

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Typical Applications for the XC3S4000-4FG900C

The XC3S4000-4FG900C is well suited for a broad range of applications across multiple industries:

Embedded Processing & Control

• Soft-processor implementations (MicroBlaze, PicoBlaze)
• Motor control and industrial automation controllers
• Custom SoC (System-on-Chip) designs

Communications & Networking

• Ethernet MAC/PHY bridging
• UART, SPI, I²C, and custom serial protocol engines
• Packet processing and header parsing

Digital Signal Processing

• FIR and IIR filter banks
• FFT/IFFT engines leveraging on-chip multipliers
• Image and video processing pipelines

Test & Measurement

• High-speed data acquisition front ends
• Protocol analysis and debugging
• Pattern generation and logic analysis

Consumer & Industrial Electronics

• Display controllers (LCD, LVDS)
• RAID and storage controllers
• Automotive and industrial sensor interfaces

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Design Tools & Development Resources

AMD Xilinx provides a comprehensive toolchain and IP library for the Spartan-3 family:

Configuration can be stored in an external SPI flash, BPI parallel NOR flash, or EEPROM. The device re-configures from non-volatile memory at power-on in milliseconds.

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Power Consumption Guidelines

The XC3S4000-4FG900C operates from a 1.2V core supply. Actual power varies significantly based on toggle rate, utilization, and I/O switching activity. Xilinx’s XPower Estimator tool provides accurate pre-layout power estimates.

Proper decoupling with low-ESR capacitors (100nF ceramic per power pin, bulk 10–47µF) is essential for stable operation at high frequencies.

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PCB Design Considerations for XC3S4000-4FG900C

When designing a PCB for the XC3S4000-4FG900C in the FG900 package, engineers should consider:

• Minimum 6-layer PCB to accommodate power planes, signal routing, and BGA fanout
• Via-in-pad or dog-bone escape routing for the 1.0mm pitch BGA
• Ground pour beneath the package connected through vias for thermal dissipation
• Separate VCCINT and VCCO power planes to prevent noise coupling
• 100nF decoupling capacitors placed as close as possible to each power ball
• Consult Xilinx UG112 – PCB Design Guide for Spartan-3 FPGAs for detailed layout rules

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Frequently Asked Questions (FAQ)

Q: What is the difference between XC3S4000-4FG900C and XC3S4000-4FG900I? A: The suffix “C” denotes the Commercial temperature grade (0°C to +85°C), while “I” denotes the Industrial grade (–40°C to +100°C). All logic and I/O resources are identical; only the guaranteed operating temperature range differs.

Q: Is the XC3S4000-4FG900C still in production? A: The Spartan-3 family has reached end-of-life status with Xilinx/AMD. However, authorized distributors and component brokers continue to carry existing inventory. For new designs, AMD recommends migrating to the Spartan-7 or Artix-7 families.

Q: Can the XC3S4000-4FG900C be used with Vivado? A: No. The Spartan-3 family is supported only by the legacy Xilinx ISE Design Suite 14.7. Vivado does not support devices older than the 7-Series.

Q: What configuration PROM is compatible with the XC3S4000-4FG900C? A: Common choices include the Xilinx XCF32P (Platform Flash PROM) or compatible SPI serial flash devices. The XC3S4000 requires approximately 12 Mbits of configuration storage.

Q: What is the maximum I/O frequency for LVDS pairs? A: LVDS data rates up to approximately 622 Mbps are achievable with the XC3S4000 using source-synchronous clocking techniques and proper PCB impedance matching.

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Summary

The XC3S4000-4FG900C remains a capable and widely understood FPGA for engineers maintaining or extending existing Spartan-3 based designs. Its combination of 4 million system gates, 1,728 Kbits of block RAM, 96 hardware multipliers, and 622 user I/Os in a manageable 900-ball BGA form factor makes it a versatile platform. While new projects should consider the more modern Spartan-7 or Artix-7 families for longevity, the XC3S4000-4FG900C continues to serve reliably in deployed systems worldwide.