The XC3S400-5PQ208C is a high-performance, cost-optimized field-programmable gate array (FPGA) from AMD Xilinx, part of the popular Spartan-3 family. Designed for high-volume, cost-sensitive applications, this device delivers robust logic density, flexible I/O, and reliable operation — making it a go-to choice for engineers seeking an affordable yet capable Xilinx FPGA solution.

---

What Is the XC3S400-5PQ208C?

The XC3S400-5PQ208C is a 400K system gate Spartan-3 FPGA housed in a 208-pin Plastic Quad Flat Pack (PQFP) package. The “-5” speed grade indicates a standard commercial performance tier, while the “C” suffix denotes a commercial temperature range (0°C to +85°C). It is manufactured using a 90nm process technology and targets a wide range of embedded control, digital signal processing, and interface bridging applications.

---

XC3S400-5PQ208C Key Specifications

General Specifications

---

Logic Resources

---

I/O and Interfacing

---

Package Dimensions

---

XC3S400-5PQ208C Functional Description

#### Architecture Overview

The Spartan-3 architecture is built around a matrix of Configurable Logic Blocks (CLBs), each containing four slices with two 4-input LUTs (Look-Up Tables) and two flip-flops per slice. This makes the XC3S400-5PQ208C suitable for implementing complex combinational and sequential logic efficiently.

The 16 dedicated 18×18 hardware multipliers accelerate DSP functions such as filtering and arithmetic without consuming CLB resources. Four Digital Clock Managers (DCMs) allow precise clock synthesis, phase shifting, and frequency division — critical for multi-clock domain designs.

#### Block RAM

With 288 Kbits of block RAM organized as sixteen 18Kbit dual-port memories, the XC3S400-5PQ208C supports on-chip data buffering, FIFOs, lookup tables, and small embedded memories. Each block RAM can be configured in various width and depth combinations, from 16K×1 to 512×36.

#### I/O Flexibility

The device supports a wide array of single-ended and differential I/O standards, enabling direct interfacing to DDR memory, processors, and communication buses. The four independent I/O banks allow different voltage standards to coexist on the same device, offering system-level flexibility without external level-shifting logic.

---

XC3S400-5PQ208C Ordering Information

---

Comparison: XC3S400 vs Other Spartan-3 Devices

The XC3S400-5PQ208C occupies a sweet spot in the Spartan-3 lineup — offering substantially more resources than entry-level devices while remaining cost-effective compared to higher-density parts. In the PQ208 package, the maximum user I/Os are limited to 141 (compared to 264 in larger packages), making it ideal for mid-complexity designs with moderate pin-count requirements.

---

Supported I/O Standards

---

Typical Applications of the XC3S400-5PQ208C

The XC3S400-5PQ208C is widely used across industries where reliable, reprogrammable logic is needed at a low cost:

• Industrial Control Systems – Motor controllers, PLC I/O expansion, sensor interface logic
• Communications Equipment – Protocol bridges, UART/SPI/I2C multi-interface controllers
• Consumer Electronics – Display controllers, audio/video processing pipelines
• Automotive Systems – Body control modules, diagnostic interfaces (at extended temperature variants)
• Test & Measurement – Logic analyzers, waveform generators, data acquisition front-ends
• Embedded Processor Systems – MicroBlaze soft-processor implementations, DMA controllers
• Cryptography & Security – Hardware-accelerated AES, SHA implementations

---

Development Tools and Support

#### Xilinx ISE Design Suite

The XC3S400-5PQ208C is supported by Xilinx ISE (Integrated Synthesis Environment), which provides:

• HDL synthesis (VHDL / Verilog)
• Place-and-route tools
• Timing analysis and simulation
• ChipScope Pro in-circuit debugger

Note: ISE is a legacy tool suite. While it fully supports Spartan-3 devices, Xilinx Vivado does not support the Spartan-3 family. ISE 14.7 is the last version and remains available from AMD Xilinx.

#### Programming and Configuration

---

Power Consumption Overview

The XC3S400-5PQ208C is designed for low static power consumption, making it suitable for power-sensitive embedded applications. Dynamic power depends on design activity, clock frequency, and I/O switching.

---

XC3S400-5PQ208C vs XC3S400-4PQ208C vs XC3S400-5PQG208C

Choose the XC3S400-5PQ208C when standard commercial operating conditions, a -5 speed grade, and the 208-pin PQFP footprint meet your design requirements.

---

Why Choose the XC3S400-5PQ208C?

• ✅ Proven Spartan-3 Architecture – Millions deployed in production designs worldwide
• ✅ Cost-Effective Logic Density – 400K gates at a low price point vs. newer families
• ✅ Flexible I/O – Wide voltage standard support for multi-interface designs
• ✅ Sufficient DSP Resources – 16 hardware multipliers and 288 Kbits BRAM for signal processing
• ✅ Easy to Source – Available from DigiKey, Mouser, Arrow, and other global distributors
• ✅ Extensive Community Support – Decades of application notes, reference designs, and forum resources

---

Frequently Asked Questions (FAQ)

Q: Is the XC3S400-5PQ208C still in production? The Spartan-3 family is considered mature/end-of-life by AMD Xilinx. While new production may be limited, the XC3S400-5PQ208C remains widely available through authorized distributors and the secondary market.

Q: What is the difference between XC3S400-5PQ208C and XC3S400-5PQG208C? The “G” in XC3S400-5PQG208C denotes a lead-free (RoHS compliant) package. The XC3S400-5PQ208C uses standard SnPb (tin-lead) solder. Functionally, both devices are identical.

Q: Can I use Vivado to program the XC3S400-5PQ208C? No. AMD Vivado does not support Spartan-3 devices. Use Xilinx ISE 14.7, the final release of the legacy tool suite, which fully supports the XC3S400.

Q: What configuration PROM is recommended for the XC3S400? Common options include the Xilinx XCF02S, XCF04S, or compatible SPI flash devices. The PROM should have sufficient capacity for the XC3S400 bitstream (~1.85 Mbit).

Q: What is the maximum operating frequency? The maximum clock frequency depends on the design’s critical path. The DCM can generate clocks up to 200+ MHz for internal logic, though typical system frequencies range from 50 MHz to 133 MHz depending on the application complexity.

---

Summary

The XC3S400-5PQ208C is a reliable, well-understood FPGA ideal for engineers who need a cost-effective programmable logic solution for commercial-temperature applications. With 8,064 logic cells, 288 Kbits of block RAM, 16 hardware multipliers, four DCMs, and support for a broad range of I/O standards — all in a 208-pin PQFP footprint — this device continues to serve countless production and prototyping designs across industrial, communications, and consumer electronics markets.

Whether you are maintaining an existing Spartan-3 design or evaluating this part for a new project, the XC3S400-5PQ208C offers a proven, field-tested solution backed by decades of Xilinx ecosystem support.