The XC3S50-4PQG208I is a high-performance, low-cost field-programmable gate array (FPGA) from the Xilinx Spartan-3 family, now part of AMD’s product portfolio. Designed for cost-sensitive applications that require flexible programmable logic, this device delivers reliable digital system integration in a compact 208-pin PQFP package. Whether you are developing embedded systems, communications hardware, or industrial control solutions, the XC3S50-4PQG208I offers the right balance of logic density, I/O flexibility, and operating speed.

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What Is the XC3S50-4PQG208I?

The XC3S50-4PQG208I belongs to the Xilinx Spartan-3 FPGA series — one of the most widely deployed FPGA families in the world. The “50” in the part number designates 50,000 system gates, “4” denotes the speed grade (-4, the slowest of the Spartan-3 speed grades, optimized for power efficiency and cost), “PQG208” refers to the 208-pin Plastic Quad Flat Pack (PQFP) package, and “I” indicates an industrial temperature range (-40°C to +85°C).

If you are looking for a proven, cost-effective Xilinx FPGA for your next design, the XC3S50-4PQG208I is an excellent entry point into programmable logic.

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XC3S50-4PQG208I Key Specifications

General Device Overview

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Logic Resources

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I/O Characteristics

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Timing and Performance

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Package Dimensions and Mechanical Data

The PQG208 package is a 208-pin Plastic Quad Flat Pack (PQFP), also referred to as a TQFP-208. It is a surface-mount package with leads on all four sides.

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XC3S50-4PQG208I: Industrial Temperature Grade Explained

The suffix “I” in XC3S50-4PQG208I designates the Industrial temperature range, which covers -40°C to +85°C. This is critical for applications where the device must function reliably in harsh or variable environments — such as factory automation, outdoor telecommunications, and transportation systems.

The industrial-grade XC3S50-4PQG208I is well-suited for designs that must pass extended operating condition tests and certifications required in aerospace ground support, medical instrumentation, and rugged industrial environments.

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Spartan-3 FPGA Architecture: How the XC3S50 Is Built

Configurable Logic Blocks (CLBs)

The fundamental building block of the Spartan-3 FPGA is the Configurable Logic Block (CLB). Each CLB contains two slices, and each slice contains:

• Two 4-input Look-Up Tables (LUTs)
• Two flip-flops
• Dedicated carry logic for arithmetic operations
• Wide-function multiplexers

The XC3S50 provides 768 slices, giving designers a highly flexible fabric for implementing combinational and sequential digital logic.

Block RAM (BRAM)

The XC3S50-4PQG208I features 72 Kb of on-chip block RAM organized as two 18 Kb true dual-port RAM blocks. Block RAM can be configured as:

• Simple dual-port RAM
• True dual-port RAM
• ROM (read-only memory)
• FIFO buffers

Digital Clock Managers (DCMs)

Two integrated Digital Clock Managers allow designers to:

• Eliminate clock skew across the device
• Multiply or divide input clock frequencies
• Phase-shift clocks for timing alignment
• Generate multiple clock domains from a single source

Multipliers

Four dedicated 18×18-bit hardware multipliers accelerate DSP-style operations such as filtering, correlation, and arithmetic-heavy control loops — without consuming CLB resources.

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Supported I/O Standards

The XC3S50-4PQG208I supports a wide range of single-ended and differential I/O standards, making it compatible with diverse system-level interfaces.

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Ordering Information and Part Number Breakdown

Understanding the full part number helps engineers quickly confirm they have the correct device for their design.

The “G” in “PQG208” specifically indicates RoHS-compliant, lead-free packaging — an important distinction for modern supply chains and regulatory compliance (EU RoHS Directive, WEEE).

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XC3S50-4PQG208I Typical Applications

The XC3S50-4PQG208I is designed for cost-sensitive, high-volume applications where programmable logic provides significant advantage over fixed-function ASICs. Common use cases include:

Embedded Systems and Microprocessor Interfacing

• Soft-core processor implementation (MicroBlaze or PicoBlaze)
• Bus bridging between SPI, I2C, UART, and parallel interfaces
• Custom peripheral controllers for MPU/MCU systems

Communications and Networking

• Protocol conversion (RS-485, CAN, Ethernet MAC glue logic)
• Framing and error detection for serial data streams
• Physical layer control state machines

Industrial Control and Automation

• Motor drive control (PWM generation, encoder decoding)
• PLC I/O expansion
• Safety monitoring and interlocking logic

Test and Measurement Equipment

• Signal capture and pre-processing
• Pattern generation for automated test equipment (ATE)
• Glue logic and bus arbitration in bench instruments

Consumer and Medical Electronics

• Display controller interfaces
• Real-time signal conditioning pipelines
• Custom state machines for medical device control (with appropriate validation)

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Configuration Options for the XC3S50-4PQG208I

Like all Spartan-3 devices, the XC3S50-4PQG208I supports several configuration modes. The bitstream is loaded at power-up and can be refreshed in-system.

Xilinx provides dedicated configuration PROMs (XCFxxS and XCFxxP series) that pair directly with Spartan-3 FPGAs for standalone, self-booting designs.

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Development Tools and Design Flow

Xilinx ISE Design Suite

The XC3S50-4PQG208I is supported by the Xilinx ISE Design Suite (Integrated Synthesis Environment), which provides:

• HDL synthesis (VHDL and Verilog)
• Place-and-route (PAR)
• Timing analysis and static timing constraints
• iMPACT for configuration and JTAG programming

Note: ISE has reached end-of-life but remains fully functional for Spartan-3 devices. Xilinx Vivado does not support Spartan-3; ISE WebPACK (free) is the correct tool.

Simulation Support

• ModelSim (Mentor)
• ISIM (Xilinx built-in)
• Aldec Active-HDL

IP Cores Available

• PicoBlaze 8-bit soft processor
• MicroBlaze 32-bit soft processor (with constraints on small devices)
• FIFO generators
• Memory interface generators
• Communication IP (UART, SPI, I2C)

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Power Consumption Guidelines

Total power consumption varies significantly based on design activity, clock frequency, and I/O loading. Xilinx XPower Estimator (XPE) is the recommended tool for estimating power budgets.

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Comparison: XC3S50 vs. Other Spartan-3 Devices

The XC3S50 is the entry-level device in the Spartan-3 family, ideal for prototyping, glue logic, and designs with moderate logic requirements.

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Why Choose the XC3S50-4PQG208I?

• Industrial Reliability: The -I temperature grade ensures stable operation from -40°C to +85°C, meeting the demands of industrial environments.
• Cost-Effective Programmability: As an entry-level Spartan-3 device, the XC3S50 offers FPGA flexibility at a fraction of the cost of higher-density devices.
• Standard Form Factor: The 208-pin PQFP package is widely supported by PCB manufacturers and assembly houses globally.
• Lead-Free Compliance: RoHS-compliant packaging meets international environmental regulations.
• Mature Ecosystem: Decades of community support, application notes, reference designs, and available IP cores.
• Long Production History: Spartan-3 devices have an extensive production track record, with a wide availability through distributors and the secondary market.

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Frequently Asked Questions (FAQ)

Q: Is the XC3S50-4PQG208I obsolete? A: The Spartan-3 family is considered a mature/legacy product line by AMD (Xilinx). While it may no longer be in active volume production, the XC3S50-4PQG208I remains widely available through authorized distributors and authorized component brokers. Always source from reputable suppliers to avoid counterfeit parts.

Q: What is the difference between XC3S50-4PQG208C and XC3S50-4PQG208I? A: The only difference is the operating temperature range. The “C” suffix is commercial grade (0°C to +85°C), while the “I” suffix is industrial grade (-40°C to +85°C). The “I” grade is tested across a wider temperature range and is recommended for harsh environments.

Q: Can I program the XC3S50-4PQG208I with Vivado? A: No. Xilinx Vivado does not support Spartan-3 devices. You must use the Xilinx ISE Design Suite (version 14.7 is the final release, available as free WebPACK).

Q: What configuration PROM is compatible with XC3S50-4PQG208I? A: Xilinx XCF01S (1 Mbit), XCF02S (2 Mbit), or equivalent third-party SPI/parallel PROMs. The XCF01S is commonly used with the XC3S50 in master serial mode.

Q: Is the XC3S50-4PQG208I RoHS compliant? A: Yes. The “G” in the package designation (PQG208) confirms lead-free, RoHS-compliant assembly.

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Summary

The XC3S50-4PQG208I is a mature, proven, and widely available entry-level Spartan-3 FPGA from AMD (Xilinx). With 50,000 system gates, 768 CLB slices, 72 Kb of block RAM, 4 hardware multipliers, and 124 user I/O pins in a 208-pin PQFP package, it delivers solid programmable logic capability for industrial-grade applications. Its -40°C to +85°C temperature range, RoHS-compliant packaging, broad I/O standard support, and rich development tool ecosystem make it a dependable choice for engineers designing embedded systems, communications hardware, and industrial control equipment.

For engineers and procurement teams looking to source or evaluate this component, always verify authenticity through authorized distribution channels and confirm the exact part marking against the Xilinx/AMD datasheet (DS099).