The XC3S400-4PQ208C is a high-performance, cost-optimized Field-Programmable Gate Array (FPGA) from Xilinx’s (now AMD) Spartan-3 family. Built on advanced 90nm CMOS technology, this device delivers 400,000 system gates in a compact 208-pin PQFP package. It is a popular choice for engineers designing high-volume, cost-sensitive consumer electronics, industrial control systems, and embedded applications. If you are looking for a reliable Xilinx FPGA for your next project, the XC3S400-4PQ208C is a proven solution worth considering.
What Is the XC3S400-4PQ208C?
The XC3S400-4PQ208C is part of the Xilinx Spartan-3 FPGA family — an eight-member series spanning densities from 50,000 to five million system gates. The “XC3S400” designation indicates 400K system gates, the “-4” indicates speed grade 4, “PQ208” refers to the 208-pin Plastic Quad Flat Pack (PQFP) package, and the final “C” denotes a commercial temperature range (0°C to +85°C). This device is manufactured using 90nm process technology and operates at a core voltage of 1.2V.
XC3S400-4PQ208C Key Specifications
Overview Specifications Table
| Parameter |
Value |
| Manufacturer |
Xilinx (AMD) |
| Part Number |
XC3S400-4PQ208C |
| Product Family |
Spartan-3 |
| Technology |
FPGA (Field-Programmable Gate Array) |
| Process Node |
90nm CMOS |
| System Gates |
400,000 |
| Logic Cells (Equivalent) |
8,064 |
| Maximum Frequency |
630 MHz |
| Core Supply Voltage |
1.2V |
| Package Type |
208-Pin PQFP (Plastic Quad Flat Pack) |
| I/O Pins (User) |
141 |
| Temperature Range |
0°C to +85°C (Commercial) |
| RoHS Compliance |
Not Compliant (standard version) |
| Speed Grade |
-4 |
Logic Resources Table
| Resource |
Quantity |
| Configurable Logic Blocks (CLBs) |
896 |
| Slices per CLB |
4 |
| Total Slices |
3,584 |
| 4-Input Look-Up Tables (LUTs) |
7,168 |
| Flip-Flops |
7,168 |
| Maximum Distributed RAM |
56 Kb |
Memory & DSP Resources Table
| Resource |
Quantity |
| Block RAM (18 Kbit each) |
16 blocks |
| Total Block RAM |
288 Kbit |
| Dedicated Multipliers (18×18) |
16 |
| Digital Clock Managers (DCMs) |
4 |
I/O and Packaging Table
| Parameter |
Value |
| User I/O Pins |
141 |
| I/O Banks |
4 |
| Package |
208-pin PQFP |
| Package Dimensions |
28mm × 28mm (nominal) |
| Differential I/O Pairs |
Up to 68 |
| Supported I/O Standards |
26 (including LVTTL, LVCMOS, SSTL, HSTL, LVDS, RSDS) |
| DDR Register Support |
Yes |
| DCI (Digitally Controlled Impedance) |
Yes |
XC3S400-4PQ208C Part Number Decoder
Understanding the part number helps confirm you are ordering the correct variant:
| Code Segment |
Meaning |
| XC |
Xilinx Commercial IC |
| 3S |
Spartan-3 Family |
| 400 |
400K System Gates |
| -4 |
Speed Grade 4 |
| PQ |
Plastic Quad Flat Pack (PQFP) |
| 208 |
208 Pins |
| C |
Commercial Temperature (0°C to +85°C) |
Note: The lead-free (RoHS compliant) Pb-free version of this part is the XC3S400-4PQG208C — note the additional “G” in the package designator.
XC3S400-4PQ208C Features & Capabilities
#### Configurable Logic Blocks (CLBs)
The XC3S400-4PQ208C contains 896 CLBs, each housing four slices. Every slice includes two 4-input LUTs, two storage elements (flip-flops or latches), carry logic, and dedicated arithmetic resources. The left-hand slices within each CLB additionally support Distributed RAM and 16-bit shift register (SRL16) functions, providing flexible on-chip memory options without consuming block RAM resources.
#### Block RAM
Sixteen 18-Kbit dual-port block RAM modules provide 288 Kbit of total on-chip RAM. Each block RAM can be configured in various width-depth combinations (e.g., 16K×1, 8K×2, 1K×18, 512×36). Each block RAM is paired with a dedicated 18×18-bit multiplier, enabling high-performance DSP operations without routing delays.
#### Digital Clock Managers (DCMs)
Four on-chip DCMs deliver robust clock management. Each DCM can eliminate clock distribution delays, synthesize new frequencies, perform phase shifting, and support spread-spectrum clocking. The DCMs accept input frequencies across a wide range and are essential for multi-clock-domain designs.
#### I/O Block (IOB) Architecture
Each IOB supports bidirectional data flow and 3-state operation. The XC3S400-4PQ208C supports 26 single-ended and differential I/O standards, including LVTTL, LVCMOS, PCI, SSTL2, SSTL18, HSTL, LVDS, RSDS, MINI_LVDS, and LVPECL. Digitally Controlled Impedance (DCI) provides automatic on-chip termination, eliminating the need for external resistors on high-speed interfaces and simplifying board design.
#### Configuration Options
The Spartan-3 FPGA stores configuration data externally and loads it at power-up using one of five modes: Master Parallel, Slave Parallel, Master Serial, Slave Serial, and Boundary Scan (JTAG). This flexibility supports a wide range of system configurations, from simple serial PROMs to parallel flash storage.
XC3S400-4PQ208C vs Other Spartan-3 Variants
| Part Number |
Gates |
I/O Pins |
Package |
Temp Range |
Lead-Free |
| XC3S400-4PQ208C |
400K |
141 |
208 PQFP |
Commercial (0–85°C) |
No |
| XC3S400-4PQG208C |
400K |
141 |
208 PQFP |
Commercial (0–85°C) |
Yes |
| XC3S400-4PQ208I |
400K |
141 |
208 PQFP |
Industrial (–40–100°C) |
No |
| XC3S400-5PQ208C |
400K |
141 |
208 PQFP |
Commercial |
No (faster speed grade) |
| XC3S1000-4PQ208C |
1M |
173 |
208 PQFP |
Commercial |
No |
Typical Applications for XC3S400-4PQ208C
The XC3S400-4PQ208C is widely used in applications where cost efficiency, moderate logic density, and versatile I/O standards are required:
- Consumer Electronics – Set-top boxes, digital cameras, portable media players
- Industrial Control – Motor control, PLC expansion, sensor interfaces
- Communications – Protocol bridging, data serialization/deserialization, line cards
- Automotive (non-safety-critical) – Infotainment systems, body electronics (use XA version for automotive-grade)
- Education & Prototyping – FPGA development boards, university lab kits, hobbyist projects
- Embedded Systems – Co-processing, hardware acceleration, glue logic replacement
XC3S400-4PQ208C Ordering and Availability
| Parameter |
Detail |
| DigiKey Part Number |
122-1385-ND |
| Manufacturer Part Number |
XC3S400-4PQ208C |
| Manufacturer |
AMD (formerly Xilinx) |
| Category |
Embedded – FPGAs (Field Programmable Gate Array) |
| Series |
Spartan-3 |
| Status |
Active / Legacy (check distributor for stock) |
| Moisture Sensitivity Level (MSL) |
3 / 168 hours |
Design Tools & Programming Support
The XC3S400-4PQ208C is supported by Xilinx’s legacy ISE Design Suite, which provides synthesis, implementation, simulation, and bitstream generation for Spartan-3 devices. While newer families use Vivado, Spartan-3 designs are developed and maintained in ISE. Key tool support includes:
- Synthesis: XST (Xilinx Synthesis Technology), Synplify Pro
- Simulation: ISim, ModelSim
- Implementation: Map, Place-and-Route (PAR), Bitgen
- Programming: iMPACT (JTAG and configuration file programming)
- Constraint Files: UCF (User Constraints File) format
Frequently Asked Questions (FAQ)
Q: What is the difference between XC3S400-4PQ208C and XC3S400-4PQG208C? The only difference is the lead-free (RoHS) compliance. The “G” in XC3S400-4PQG208C indicates a Pb-free package. Electrical and performance specifications are identical.
Q: Is the XC3S400-4PQ208C still in production? The Spartan-3 family is a mature/legacy product line. Check authorized distributors such as DigiKey, Mouser, or Arrow for current stock availability.
Q: What voltage does the XC3S400-4PQ208C require? The core supply (VCCINT) is 1.2V. I/O supply voltages (VCCO) vary from 1.2V to 3.3V depending on the selected I/O standard.
Q: Can the XC3S400-4PQ208C be used in industrial temperature environments? The “C” suffix indicates a commercial temperature range (0°C to +85°C). For industrial applications requiring –40°C to +100°C operation, use the XC3S400-4PQ208I variant.
Q: What configuration PROM is compatible with the XC3S400-4PQ208C? Compatible Xilinx PROMs include the XCF series (Platform Flash), such as the XCF02S or XCF04S, which are commonly paired with Spartan-3 devices for Master Serial configuration.
Summary
The XC3S400-4PQ208C is a well-established, cost-effective FPGA solution offering 400K system gates, 141 user I/O pins, 16 block RAMs, 16 dedicated multipliers, and 4 DCMs in a standard 208-pin PQFP package. Its support for 26 I/O standards, DDR registers, and DCI makes it suitable for a broad range of embedded and communications applications. Whether you are upgrading an existing Spartan-3 design or starting a new cost-sensitive project, the XC3S400-4PQ208C remains a capable and readily available choice in the programmable logic market.
