The XC3S400-4PQ208I is a high-performance, cost-optimized Field Programmable Gate Array (FPGA) from Xilinx (now AMD), part of the widely adopted Spartan-3 family. Designed for industrial-grade applications, this device delivers 400,000 system gates, 208-pin PQFP packaging, and a –4 speed grade, making it an ideal choice for embedded systems, digital signal processing, and high-volume production designs. Whether you’re an electronics engineer searching for a reliable Xilinx FPGA or a procurement specialist sourcing components for industrial applications, this guide covers everything you need to know.
What Is the XC3S400-4PQ208I?
The XC3S400-4PQ208I belongs to Xilinx’s Spartan-3 series, a family of FPGAs engineered to reduce system costs while providing abundant logic resources. The “I” suffix designates the industrial temperature range (–40°C to +100°C), making it suitable for demanding environments such as automotive, telecom, and industrial control systems.
Key Highlights
- Part Number: XC3S400-4PQ208I
- Manufacturer: AMD (formerly Xilinx)
- Series: Spartan-3
- Logic Gates: 400,000
- Package: 208-pin PQFP (Plastic Quad Flat Pack)
- Speed Grade: –4
- Temperature Grade: Industrial (–40°C to +100°C)
- RoHS Status: RoHS Compliant
XC3S400-4PQ208I Full Technical Specifications
The table below provides a complete overview of the electrical and physical specifications for the XC3S400-4PQ208I.
| Parameter |
Specification |
| Manufacturer / Brand |
AMD (Xilinx) |
| Part Number |
XC3S400-4PQ208I |
| FPGA Family |
Spartan-3 |
| Number of Logic Gates |
400,000 |
| Number of CLBs (Configurable Logic Blocks) |
3,584 |
| Number of Slices |
7,168 |
| Flip-Flops |
14,336 |
| Max. Distributed RAM |
56 Kb |
| Block RAM |
288 Kb (16 blocks × 18 Kb) |
| DSP Multipliers |
16 × 18×18 hardware multipliers |
| Maximum User I/O Pins |
141 |
| Digital Clock Managers (DCMs) |
4 |
| Package Type |
PQFP (Plastic Quad Flat Pack) |
| Package Body Size |
208-pin |
| Speed Grade |
–4 |
| Operating Voltage (VCCINT) |
1.2 V |
| I/O Voltage (VCCO) |
1.2 V – 3.3 V |
| Temperature Range |
–40°C to +100°C (Industrial) |
| Process Technology |
90 nm |
| RoHS Compliant |
Yes |
| Mounting Type |
Surface Mount |
XC3S400-4PQ208I Logic & Memory Resources
Understanding the internal architecture helps engineers plan designs effectively. The Spartan-3 architecture offers a rich set of programmable resources.
Configurable Logic Blocks (CLBs)
| Resource |
Count |
| CLBs |
3,584 |
| Slices per CLB |
2 |
| Total Slices |
7,168 |
| LUTs per Slice |
2 |
| Total LUTs |
14,336 |
| Flip-Flops |
14,336 |
Memory Resources
| Memory Type |
Capacity |
| Block RAM (BRAM) |
288 Kb total |
| Number of BRAM Blocks |
16 |
| Per Block RAM Size |
18 Kb |
| Distributed RAM |
56 Kb |
DSP and Clock Resources
| Resource |
Details |
| Hardware Multipliers |
16 × (18×18-bit) |
| Digital Clock Managers (DCMs) |
4 |
| Global Clock Networks |
24 |
XC3S400-4PQ208I I/O and Packaging Details
Pin Configuration
| Parameter |
Value |
| Package |
PQ208 (PQFP-208) |
| Total Pins |
208 |
| Maximum User I/O |
141 |
| Differential I/O Pairs |
68 |
| Package Dimensions |
28 mm × 28 mm |
| Pitch |
0.5 mm |
| Mounting |
Surface Mount (SMT) |
Supported I/O Standards
The XC3S400-4PQ208I supports a wide range of industry-standard I/O signaling protocols:
| I/O Standard |
Type |
| LVTTL |
Single-ended |
| LVCMOS 3.3V / 2.5V / 1.8V / 1.5V |
Single-ended |
| PCI (3.3V) |
Single-ended |
| SSTL2 / SSTL3 |
Differential |
| LVDS |
Differential |
| LVPECL |
Differential |
| GTL / GTL+ |
Single-ended |
| HSTL Class I / II |
Single-ended |
XC3S400-4PQ208I Electrical Characteristics
| Parameter |
Min |
Typical |
Max |
Unit |
| Core Supply Voltage (VCCINT) |
1.14 |
1.20 |
1.26 |
V |
| I/O Supply Voltage (VCCO) |
1.14 |
– |
3.465 |
V |
| Input Voltage (VIN) |
–0.5 |
– |
VCCO + 0.5 |
V |
| Operating Temperature (Industrial) |
–40 |
– |
+100 |
°C |
| Static Current (ICCINTQ) |
– |
~20 |
– |
mA |
XC3S400-4PQ208I Ordering Information
When purchasing the XC3S400-4PQ208I, understanding the part number structure is essential to ensure the correct variant is ordered.
Part Number Decoder
| Segment |
Value |
Meaning |
| XC |
XC |
Xilinx Commercial IC |
| 3S |
3S |
Spartan-3 Family |
| 400 |
400 |
400K System Gates |
| -4 |
–4 |
Speed Grade (–4 = slower; –5 = faster) |
| PQ |
PQ |
PQFP Package |
| 208 |
208 |
208 Total Pins |
| I |
I |
Industrial Temp Range (–40°C to +100°C) |
Available Variants Comparison
| Part Number |
Gates |
Package |
Speed Grade |
Temp Grade |
| XC3S400-4PQ208C |
400K |
PQFP-208 |
–4 |
Commercial (0°C to +85°C) |
| XC3S400-4PQ208I |
400K |
PQFP-208 |
–4 |
Industrial (–40°C to +100°C) |
| XC3S400-5PQ208I |
400K |
PQFP-208 |
–5 |
Industrial |
| XC3S400-4FT256I |
400K |
FTBGA-256 |
–4 |
Industrial |
XC3S400-4PQ208I vs Other Spartan-3 Devices
Choosing the right device size within the Spartan-3 family depends on your gate count, I/O, and memory requirements.
| Device |
Gates |
Slices |
Block RAM |
Max I/O |
Multipliers |
| XC3S50 |
50K |
1,728 |
72 Kb |
124 |
4 |
| XC3S200 |
200K |
4,320 |
144 Kb |
141 |
12 |
| XC3S400 |
400K |
7,168 |
288 Kb |
141 |
16 |
| XC3S1000 |
1,000K |
15,360 |
432 Kb |
391 |
24 |
| XC3S1500 |
1,500K |
29,952 |
576 Kb |
487 |
32 |
| XC3S4000 |
4,000K |
62,208 |
1,728 Kb |
784 |
96 |
Key Features and Benefits of the XC3S400-4PQ208I
#### Cost-Optimized Design for High-Volume Production
The Spartan-3 series was specifically architected by Xilinx to deliver the lowest cost per logic cell in the FPGA industry at the time of its release. The XC3S400-4PQ208I is an excellent choice for cost-sensitive, high-volume designs that still require substantial programmable logic.
#### Industrial Temperature Reliability
The “I” suffix guarantees operation across the full industrial temperature range of –40°C to +100°C. This makes the XC3S400-4PQ208I robust enough for use in factory automation, telecommunications equipment, automotive electronics, and outdoor embedded systems where commercial-grade parts would fail.
#### Dedicated Hardware Multipliers for DSP Workloads
With 16 embedded 18×18-bit hardware multipliers, the XC3S400-4PQ208I efficiently handles digital signal processing (DSP) tasks including filtering, FFT computation, and motor control algorithms—without consuming valuable CLB resources.
#### Flexible I/O with Multiple Voltage Standards
Support for 12+ I/O standards allows the XC3S400-4PQ208I to interface directly with processors, memory buses, sensors, and communication controllers operating at different voltage levels (1.2V to 3.3V), reducing the need for external level translators.
#### Four Digital Clock Managers (DCMs)
The four on-chip DCMs provide clock multiplication, division, phase shifting, and deskewing capabilities, enabling complex clocking architectures without external PLL chips.
Typical Applications of the XC3S400-4PQ208I
The XC3S400-4PQ208I is used across a broad spectrum of industries and applications:
| Application Area |
Use Case |
| Industrial Automation |
Motor controllers, PLC modules, sensor interfaces |
| Telecommunications |
Protocol converters, framing engines, line cards |
| Embedded Systems |
Co-processor acceleration, bus bridging |
| Test & Measurement |
Data acquisition systems, signal generators |
| Consumer Electronics |
Image processing pipelines, display controllers |
| Automotive |
ADAS interface logic, CAN/LIN bus controllers |
| Medical Devices |
Patient monitoring signal processing |
| Military / Defense |
Ruggedized computing platforms |
XC3S400-4PQ208I Design & Development Tools
Xilinx (AMD) provides a complete design flow for the Spartan-3 family:
| Tool |
Purpose |
| Vivado Design Suite |
Full FPGA design, synthesis, and implementation |
| ISE Design Suite (Legacy) |
Primary legacy toolchain for Spartan-3 devices |
| XST / Synplify Pro |
RTL synthesis |
| ModelSim / Vivado Simulator |
Functional and timing simulation |
| ChipScope Pro |
In-circuit debugging |
| IMPACT / iMPACT |
Device programming via JTAG or boundary scan |
Note: The XC3S400-4PQ208I is primarily supported by Xilinx ISE Design Suite (legacy). While Vivado does not natively target Spartan-3, ISE 14.7 (the final ISE release) is freely available from AMD and fully supports this device.
PCB Design Considerations for the XC3S400-4PQ208I
When designing a PCB for the XC3S400-4PQ208I, engineers should keep the following best practices in mind:
- Decoupling Capacitors: Place 100 nF ceramic capacitors on every VCCINT and VCCO pin, as close as possible to the package body.
- Power Sequencing: VCCINT (1.2V) should be powered before or simultaneously with VCCO to prevent latch-up.
- Configuration Pins: Properly configure M0, M1, M2 mode pins to select the desired configuration mode (JTAG, Master Serial, Slave Serial, etc.).
- JTAG Access: Always expose TDI, TDO, TMS, and TCK for in-system programming and debugging.
- Signal Integrity: For differential I/O pairs (LVDS/LVPECL), maintain matched trace lengths and controlled impedance (typically 100 Ω differential).
- Ground Planes: Use solid ground planes to minimize EMI and ensure stable operation.
Configuration Modes Supported
| Mode |
M2 |
M1 |
M0 |
Description |
| Master Serial |
0 |
0 |
0 |
Reads configuration from serial flash |
| Slave Serial |
1 |
1 |
1 |
Configured by external controller |
| Master SPI |
0 |
0 |
1 |
SPI flash configuration |
| JTAG |
Any |
Any |
Any |
Always available in parallel |
| Slave SelectMAP |
1 |
1 |
0 |
Parallel microprocessor mode |
Frequently Asked Questions (FAQ)
#### What does the “I” mean in XC3S400-4PQ208I?
The “I” at the end of the part number designates the Industrial temperature grade, meaning the device is rated to operate reliably from –40°C to +100°C. The commercial-grade equivalent is XC3S400-4PQ208C, rated from 0°C to +85°C.
#### What software do I use to program the XC3S400-4PQ208I?
The XC3S400-4PQ208I is designed for use with Xilinx ISE Design Suite, specifically ISE 14.7, which is the final version and is available as a free download from AMD’s website. The device is not supported by the newer Vivado tool.
#### What is the core voltage for the XC3S400-4PQ208I?
The core supply voltage (VCCINT) is 1.2V. The I/O voltage (VCCO) is configurable from 1.2V to 3.3V depending on the I/O standard used.
#### How many user I/O pins does the XC3S400-4PQ208I have?
In the PQ208 package, the XC3S400 provides a maximum of 141 user-configurable I/O pins.
#### Is the XC3S400-4PQ208I RoHS compliant?
Yes. The XC3S400-4PQ208I is RoHS compliant and uses a lead-free package.
#### What is the difference between speed grade –4 and –5?
Speed grade –5 is faster (lower propagation delay) than –4. If your design has tight timing requirements, the –5 grade may be needed. For most standard designs, –4 is sufficient and typically lower in cost.
Conclusion
The XC3S400-4PQ208I is a proven, industrial-grade FPGA that offers an excellent balance of logic density, memory, DSP capability, and I/O flexibility in a cost-effective 208-pin PQFP package. Its –40°C to +100°C industrial temperature rating makes it a reliable choice for demanding applications in automation, telecommunications, automotive, and embedded computing. With support for 16 hardware multipliers, 288 Kb of block RAM, and four Digital Clock Managers, this Spartan-3 device remains a trusted solution for both new designs and long-lifecycle industrial platforms.
For engineers seeking a dependable and scalable programmable logic solution, the XC3S400-4PQ208I continues to be a go-to component across global industries.
