The XC3S400-5PQG208I is a high-performance, cost-optimized Xilinx FPGA from the Spartan-3 family, manufactured by AMD (formerly Xilinx). Designed for high-volume, cost-sensitive applications, this device delivers 400,000 system gates in a compact 208-pin PQFP package with industrial-grade temperature tolerance. Whether you are designing embedded control systems, digital signal processing platforms, or telecommunications equipment, the XC3S400-5PQG208I offers a compelling combination of logic density, I/O flexibility, and proven reliability.
What Is the XC3S400-5PQG208I?
The XC3S400-5PQG208I belongs to Xilinx’s Spartan-3 product line — one of the most widely deployed FPGA families in industrial and commercial electronics. The part number breaks down as follows:
| Part Number Segment |
Meaning |
| XC3S |
Xilinx Spartan-3 Family |
| 400 |
400,000 System Gates |
| 5 |
Speed Grade –5 (fastest in the Spartan-3 line) |
| PQ |
PQFP (Plastic Quad Flat Package) |
| G208 |
208-Pin Package |
| I |
Industrial Temperature Range (–40°C to +100°C) |
XC3S400-5PQG208I Key Specifications
General Specifications
| Parameter |
Value |
| Manufacturer |
AMD / Xilinx |
| Part Number |
XC3S400-5PQG208I |
| Product Family |
Spartan-3 |
| Logic Cells |
8,064 |
| System Gates |
400,000 |
| CLB Slices |
3,584 |
| CLB Flip-Flops |
7,168 |
| Maximum Distributed RAM |
56 Kb |
| Block RAM |
288 Kb |
| Dedicated Multipliers (18×18) |
16 |
| DCM (Digital Clock Managers) |
4 |
Package & Electrical Specifications
| Parameter |
Value |
| Package Type |
PQFP (Plastic Quad Flat Package) |
| Pin Count |
208 |
| User I/O Pins |
141 |
| I/O Standards Supported |
LVTTL, LVCMOS, SSTL, HSTL, GTL+, PCI, LVDS, BLVDS, ULVDS, RSDS |
| Core Supply Voltage (VCCINT) |
1.2V |
| I/O Supply Voltage (VCCIO) |
1.2V – 3.3V |
| Operating Temperature |
–40°C to +100°C (Industrial Grade) |
| RoHS Compliance |
Yes |
Speed & Timing
| Parameter |
Value |
| Speed Grade |
–5 (Fastest) |
| Maximum System Clock |
Up to ~200 MHz (design-dependent) |
| fMAX (combinatorial paths) |
Up to 326 MHz |
XC3S400-5PQG208I vs. XC3S400-4PQG208I: Speed Grade Comparison
The XC3S400-5PQG208I offers a faster speed grade compared to the –4 variant. Here is a direct comparison:
| Specification |
XC3S400-5PQG208I |
XC3S400-4PQG208I |
| Speed Grade |
–5 (Fastest) |
–4 |
| System Gates |
400,000 |
400,000 |
| Logic Cells |
8,064 |
8,064 |
| Package |
PQ208 |
PQ208 |
| Temperature Range |
Industrial (–40°C to +100°C) |
Industrial (–40°C to +100°C) |
| Typical fMAX |
Higher throughput |
Slightly lower throughput |
| Recommended Use |
High-speed designs, tight timing |
Standard-speed designs |
Tip: Choose the –5 speed grade when your design has tight setup/hold timing requirements or runs at clock frequencies above 150 MHz.
Spartan-3 Architecture Overview
CLB (Configurable Logic Blocks)
The Spartan-3 CLB architecture is built around four-input LUTs (Look-Up Tables) organized into slices. Each CLB contains two slices, and each slice contains two LUTs and two flip-flops. This architecture enables efficient implementation of:
- Combinatorial logic
- Sequential state machines
- Arithmetic operations
- Shift registers and small distributed memories
Block RAM (BRAM)
With 288 Kb of dedicated block RAM arranged in 18 Kb dual-port blocks, the XC3S400-5PQG208I supports:
- FIFOs and data buffers
- Lookup tables for DSP and communications
- Embedded processor memory (e.g., MicroBlaze soft-core)
- Configuration data storage
Dedicated Multipliers
The device features 16 dedicated 18×18 hardware multipliers, enabling high-performance DSP functions such as:
- FIR and IIR digital filters
- FFT cores
- PID controllers
- Motor control algorithms
Digital Clock Managers (DCMs)
Four integrated DCMs provide:
- Clock multiplication and division
- Phase shifting (fine-grained, 0–360°)
- Clock deskewing
- Duty cycle correction
I/O Bank Architecture and Supported Standards
The XC3S400-5PQG208I’s 141 user I/O pins are grouped into four I/O banks. Each bank can be powered independently, enabling mixed-voltage designs on a single FPGA.
| I/O Standard |
Type |
Voltage |
| LVTTL / LVCMOS |
Single-ended |
1.2V – 3.3V |
| PCI |
Single-ended |
3.3V |
| SSTL2 / SSTL3 |
Single-ended |
2.5V / 3.3V |
| HSTL |
Single-ended |
1.5V |
| GTL / GTL+ |
Single-ended |
1.2V / 1.5V |
| LVDS |
Differential |
2.5V |
| BLVDS / ULVDS / RSDS |
Differential |
2.5V |
Typical Applications for XC3S400-5PQG208I
The XC3S400-5PQG208I is well-suited for a wide range of embedded and industrial applications:
| Application Area |
Use Cases |
| Industrial Control |
Motor control, PLC I/O expansion, sensor fusion |
| Telecommunications |
Line cards, protocol bridges, framing logic |
| Digital Signal Processing |
FIR/IIR filters, FFT engines, audio processing |
| Embedded Systems |
MicroBlaze soft-core processor, co-processing |
| Test & Measurement |
Pattern generation, data capture, protocol analysis |
| Automotive Electronics |
Gateway modules, data logging (with –I grade) |
| Consumer Electronics |
Video processing, interface bridging |
FPGA Configuration Methods
The XC3S400-5PQG208I supports multiple configuration modes, providing flexibility for prototyping and production:
| Configuration Mode |
Description |
| Master Serial |
FPGA reads bitstream from SPI Flash |
| Slave Serial |
External controller drives configuration |
| Master SelectMAP |
Parallel byte-wide configuration |
| Slave SelectMAP |
Parallel byte-wide, controlled externally |
| JTAG |
Boundary scan and in-system programming |
| Master SPI |
Direct connection to SPI Flash memory |
Design Tools and Development Support
The XC3S400-5PQG208I is fully supported by AMD Xilinx’s development ecosystem:
- ISE Design Suite – Legacy toolchain with full Spartan-3 support
- Vivado Design Suite – IP integrator and simulation support
- ChipScope Pro – In-system logic analyzer
- XPower Analyzer – Power estimation tool
- MicroBlaze Soft Processor – 32-bit embedded RISC core
- PicoBlaze – Lightweight 8-bit soft processor
- IP Core Library – UART, SPI, I2C, Ethernet MAC, DDR controller, and more
Ordering Information
| Part Number |
Speed Grade |
Temperature |
Package |
Pins |
| XC3S400-5PQG208I |
–5 |
Industrial (–40°C to +100°C) |
PQFP |
208 |
| XC3S400-4PQG208I |
–4 |
Industrial (–40°C to +100°C) |
PQFP |
208 |
| XC3S400-5PQG208C |
–5 |
Commercial (0°C to +85°C) |
PQFP |
208 |
| XC3S400-4PQG208C |
–4 |
Commercial (0°C to +85°C) |
PQFP |
208 |
Why Choose the XC3S400-5PQG208I?
1. Industrial-Grade Reliability
The “I” suffix guarantees operation across the full –40°C to +100°C temperature range — essential for automotive, outdoor, and industrial environments where commercial-grade components would fail.
2. Highest Speed Grade Available
Speed grade –5 provides the fastest timing performance in the Spartan-3 400K gate family, making it the right choice when design closure requires more timing margin.
3. Proven, Mature Platform
The Spartan-3 architecture has been deployed in millions of devices worldwide. Its mature toolchain, extensive IP library, and large community make development faster and more predictable.
4. Cost-Effective Gate Density
With 400,000 system gates and 8,064 logic cells in a 208-pin PQFP, this device delivers excellent logic density per dollar — ideal for high-volume production designs.
5. Flexible I/O Voltage Support
Support for over 12 I/O standards across four independent banks means the XC3S400-5PQG208I can interface with a wide variety of legacy and modern peripherals without external level shifters.
Frequently Asked Questions (FAQ)
Q: What is the difference between XC3S400-5PQG208I and XC3S400-5PQG208C?
A: The “I” suffix denotes Industrial temperature range (–40°C to +100°C), while “C” is Commercial grade (0°C to +85°C). The logic and I/O specifications are identical.
Q: Can the XC3S400-5PQG208I run a soft-core processor?
A: Yes. The MicroBlaze 32-bit soft processor and PicoBlaze 8-bit processor are both supported and can be implemented within the available logic resources.
Q: What Flash memory is recommended for configuring the XC3S400-5PQG208I?
A: Xilinx Platform Flash (XCF series) or standard SPI NOR Flash (minimum 4 Mb) are commonly used. The bitstream size for the XC3S400 is approximately 1.7 Mb.
Q: Is the XC3S400-5PQG208I in production?
A: The Spartan-3 series is in its extended product lifecycle phase. Availability may vary by distributor; check authorized distributors for current stock and lead times.
Q: What is the JTAG pinout for in-system programming?
A: The device uses standard IEEE 1149.1 JTAG with TDI, TDO, TMS, and TCK signals on dedicated pins, compatible with Xilinx Platform Cable USB II or third-party JTAG adapters.
Conclusion
The XC3S400-5PQG208I is a robust, industrial-grade FPGA that combines the versatility of the Spartan-3 architecture with the top-tier –5 speed grade performance and a wide operating temperature range. Its 400,000 system gates, 141 user I/Os, 16 hardware multipliers, and 288 Kb block RAM make it a capable platform for everything from industrial control to embedded DSP systems. Backed by Xilinx’s mature toolchain and broad IP ecosystem, this device remains a strong choice for engineers designing cost-sensitive, high-reliability systems.
