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What is Xilinx XC6SLX25-3CSG324i FPGA ?


The Xilinx XC6SLX25-3CSG324i is a mid-range Spartan-6 series FPGA (Field Programmable Gate Array) chip optimized for cost-sensitive, high-volume applications. This article provides an overview of the XC6SLX25 FPGA including its key features, internal architecture, available development boards and example applications.

FPGA Overview

An FPGA is an integrated circuit containing programmable logic blocks and interconnects that can be configured to implement custom hardware functions. Unlike Application Specific Integrated Circuits (ASICs), the functionality of FPGAs can be changed as needed by reprogramming.

Key characteristics of FPGAs:

  • Contains configurable logic blocks (CLBs) to implement logic
  • I/O blocks provide interfacing capability
  • Interconnects route signals between logic and I/O
  • SRAM based configuration for reprogramming
  • Much lower cost compared to ASICs

This field programmability makes FPGAs ideal for fast prototyping and flexible designs.

XC6SLX25-3CSG324i Overview

The Xilinx XC6SLX25-3CSG324i FPGA has the following key features:

  • Spartan-6 mid-range FPGA series from Xilinx
  • Optimized for low-cost, minimal power consumption applications
  • 324 pin ceramic fine line surface mount CSP (chip scale package)
  • 23,038 logic cells featuring 6-input LUTs
  • 136 18Kb block RAMs
  • 8 Digital Clock Managers (DCMs)
  • 240 DSP48A1 slices with 18×18 multipliers
  • 3.2 Gbps low-power transceivers
  • Multi-voltage support 1.0V to 1.8V VCCINT/VCCAUX
  • -3 speed grade

With these specs, the XC6SLX25 FPGA offers an optimal balance of logic capacity, low cost and minimal power for space-constrained embedded applications.

Internal Architecture

The XC6SLX25 contains the following key components in its internal architecture:

Configurable Logic Blocks

The basic building block is the Configurable Logic Block (CLB) which contains:

  • 4-input LUTs for logic implementation
  • Flip flops for registering logic
  • Fast carry logic for arithmetic

CLBs are arranged in a two-dimensional array across the chip.

Block RAM

136 Kb (18K x 8) of true dual-port block RAMs distributed through the array provide local memory with two independent ports.

DSP Slices

DSP48A1 slices allow digital signal processing operations like MAC, multiply accumulate, multipliers, adders, logical functions.

Clock Management

8 DCMs provide clock synthesis, skew adjustment, jitter filtering and other clocking support.

I/O Blocks

Periphery IOBs feature support for common I/O standards like LVCMOS, LVDS, and SSTL. High speed GTP transceivers allow serial interfacing.


A flexible routing architecture connects internal components and IOBs using a combination of local, direct, global and long line interconnects spanning multiple channels.

Development Tools and Kits

Xilinx offers a full ecosystem of development tools and boards to support designs using the XC6SLX25 FPGA:

Software Tools

  • ISE Design Suite – For synthesis and place and route
  • Xilinx Platform Studio – GUI for constraint entry
  • ChipScope – Integrated logic analyzer
  • EDK – For Microblaze embedded processor development

Evaluation Kits

  • SP601 evaluation board – Features XC6SLX25 in UFBGA package, DDR2 memory, FMC connector etc.
  • SP605 board – Contains XC6SLX25 FPGA with HDMI, VGA, Ethernet etc.
  • KC705 board – Kintex-7 FPGA board also usable for Spartan-6 designs

Using these software tools and kits accelerates development and debug when leveraging the XC6SLX25 FPGA.


The optimal blend of low cost, power efficiency and logic capacity in the XC6SLX25 FPGA make it suitable for a wide range of applications including:

  • Battery powered embedded devices
  • Industrial automation and control
  • Wireless sensor systems
  • Automotive driver assistance systems
  • Space avionics
  • Video/image processing systems
  • Defense electronics
  • Test and measurement equipment
  • IoT endpoints

The XC6SLX25 allows implementing custom logic and algorithms for these applications in a small form factor.

Comparison with Other FPGAs

The XC6SLX25 sits in Xilinx’s low cost Spartan-6 FPGA series in terms of density and features. Comparisons with other major FPGA families are:

FPGAKey Characteristics
Xilinx Spartan-7Denser and higher performance successor to Spartan-6
Intel Max-10Competitor low-cost FPGA comparable to Spartan-6
Xilinx Artix-7Mid-range density and performance above Spartan-6
Xilinx Kintex-7High-end FPGA family for very demanding applications


The Xilinx XC6SLX25-3CSG324i FPGA provides a balance of low cost, power efficiency and logic capacity well suited for space-constrained embedded devices. The Spartan-6 architecture offers essential embedded peripherals like block RAM and DSP slices in an optimal configuration for control and interfacing applications. With the available software tools and development boards, the XC6SLX25 FPGA enables rapid prototyping and deployment of custom hardware designs.


What are the key differences between Spartan-6 and Spartan-7 FPGAs?

Spartan-7 offers higher density, performance and bandwidth compared to Spartan-6. Key improvements include higher LUT counts, wider block RAM, PCIe support, and faster transceivers.

What embedded peripherals are integrated in the XC6SLX25 FPGA?

Embedded peripherals in XC6SLX25 include 136 Kb block RAMs, 240 DSP slices, 8 clock management tiles, 3.2 Gbps transceivers, among other dedicated hardware blocks.

What PCB packages can the XC6SLX25 be manufactured in?

XC6SLX25 is available in multiple packages including 324-pin CSP, 484-pin FFG900 and 13×13 mm UFBGA. PCB assembly methods supported include surface mount and socketing.

What are the typical power consumption figures for the XC6SLX25 FPGA?

Typical static and dynamic power consumption is low – in the range of 100 mW – due to Spartan-6 power optimization features. Exact power depends on utilization.

Which software tools can be used to develop applications with the XC6SLX25?

Xilinx offers the ISE Design Suite for synthesis and place-and-route. Soft processors like MicroBlaze can be implemented using Xilinx EDK tools. Simulation, debug and analysis is enabled by ChipScope.

All About Xilinx XC6SLX25-3CSG324i

The Xilinx XC6SLX25-3CSG324i is an IC readily available in different grades of speed. The highest possible speed is -3 and the highest performance too. The AC and DC parameters of the IC which is utilized for defense and automotive industries are equivalent to that of ICs used for commercial purposes. The characteristics of timing for the commercial ICs with the speed of -2 grade are equivalent to that of the ICs used for commercial purposes with the same grade. However, the speed grades of -3Q and -2Q are dedicatedly utilized for the applications where there are requirements of an expanded range of temperature Q.

The characteristics of timing are the same when speed is considered for both -3 and -2 grade ICs. The characteristics of both AC and DC are dedicated to the industrial, commercial, and expanded ranges of temperature. However, specified grades of speed and devices are expected to be readily available for the expanded or industrial ranges of temperature when it comes to the ICs of defense and automotive type. The reference to any of its device names is referring to the availability of all variations of its part number. But, the -3N grade of speed is designating all of the devices that are not supporting MCB functioning. The specifications of junction temperature and entire supply voltage is a representation of the worst possible case conditions and its parameters are encompassing the most typical and common designs for various applications.

Absolute Maximum Conditions

If stress is applied beyond the rated absolute maximum rating to the device may result in its permanent damage or burnout. The stress ratings are necessary for the device to be operational and it may not perform if such conditions are not fulfilled for its operation. Furthermore, if the device is exposed to the absolute maximum ratings too frequently may also result in any irreversible damage to the device. When the eFUSE of the device is programmed, it requires a current of up to 40mA and its VFS may be in the range of 3.45V to 0V. The overshoot duration of the input/output absolute maximum limit is in the percentage of the data for that period when 3.45V is applied. The maximum possible overshoot of voltage is 4.40V. The maximum bearable temperature for soldering purposes is Tsol for the device.  

Recommended Operating Conditions


The entire range of voltages is relevant to the position of the ground or GND. To perform the device in its extended performance range while not utilizing the standard VCCINT range of voltages. But the VCCINT is not recommended to be utilized for designs that are not using MCB, LX4 devices, devices of CPG196 packages or TQG144, and -3N grade of speed. The maximum possible voltage droop VCCAUX is about 10 millivolts per milliseconds. In case when the configuration is underway, when VCCO_2 is about 1.8V then its VCCAUX must be around 2.5V. When the device of -1L is requiring VCCAUX to be 2.5V through the use of standard RSDS_33, RSDS_25, LVPECL_25, LVDS_25, PPDS_25, and BLVDS_25 input/output on its inputs then LVPECL_33 is not supposed to be implemented at -1L devices.

The configuration data is always retained by the device even in case if the VCCO is dropped to 0V and the device has the inclusion of VCCO for 3.3V, 2.5V, 1.8V, 1.5V, and 1.2V respectively. The receiver and transmitter are required to have a common supply for VCCO when it comes to the PCI system. Xilinx PCI IP is not supported by the devices with -1L speed. 100mA must not be exceeded per bank for the device. Maintenance of VBATT is also necessitated for RAM backed by the battery when the VCCAUX is not being applied. When the VCCAUX is applied to the device then VBATT could be disconnected.

eFUSE Programming Conditions

The programming of eFUSE is only supported with the help of JTAG and such specifications are only applied while programming of the AES key of eFUSE. While programming the eFUSE, it must be guaranteed that VFS is lesser or equivalent to VCCAUX. While when the eFUSE is not programmed or is not in use, it is recommended that GND and VFS must be connected. But VFS must be in the range of 3.45V to 0V. There is a requirement of a resistor RFUSE for programming the AES key of eFUSE.

Recommended DC Characteristics

The measurement of the CIN is representing using a pad of die capacitance and not including package. The maximum possible value which is specified for the worst case is processed at 25 degrees Celsius. Referring to the RDT variation IBIS model and for values at VCCAUX of 2.5V, then IBIS values of RDT seem valid for all of the ranges of temperature. Whereas, there is no requirement of VCCO2 for retention of data. The minimum value of the VCCO2 for configuration and powering on reset is about 1.65V.

Quiescent Current

The specification of conventional values for the quiescent supply current of the device is done at nominal voltage and junction temperature of 25 degrees Celsius. The devices which are used for industrial and commercial grades are also having the same values. But, its higher values are lying at 100 degrees Celsius. Xilinx XC6SLX25-3CSG324i is recommending the analysis of static power consumption through the use of power estimator software. The nominal value of VCCINT is around 1.2V and is computed through the use of the XPE tool. The typical values are often used for devices that are blank and have no pull-up resistors in their active state, no output current loads, and all input/output pins are floating and in 3-state. In case if differential signaling is utilized then the values of quiescent current can be made more precise through the utilization of XPA software.

Ramp Time of Power Supply

The minimum requirement for VCCO2 for its reset on powering-on along reconfiguration is 1.65V. The device is requiring a specific amount of supply current while powering on to ensure the initialization of the device properly. The consumption of actual current is dependent on the rate of power on the ramp for its power supply. XPA or XPE tools are utilized for estimation of the drain currents for the power supplies.




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