XC95108-7TQG100C CPLD: A Technical Guide to the Legacy 5V Workhorse

In the realm of industrial electronics repair and legacy system maintenance, few components are as vital—and as misunderstood—as the XC95108-7TQG100C. While the world has moved to low-voltage FPGAs, thousands of industrial machines, medical devices, and telecom systems built in the late 90s still rely on the robust 5V logic of the Xilinx XC9500 CPLD family.

If you are an engineer tasked with maintaining these systems, you know that finding a reliable replacement for a "blown" CPLD is only half the battle. You also need to know how to program it, what software to use, and how to ensure it is compatible with the rest of the board.

This technical guide provides a deep dive into the XC95108-7TQG100C datasheet, helping you navigate the complexities of this legacy 5V CPLD.

1.0 What is the XC95108-7TQG100C? (Datasheet Explained)

The XC95108-7TQG100C is a high-performance Complex Programmable Logic Device (CPLD). It belongs to the original Xilinx XC9500 family, which is famous for its 5V in-system programmability and non-volatile Flash technology.

1.1 The Xilinx XC9500 Family: The 5V Standard

Unlike modern FPGAs that lose their configuration when power is cut, the XC95108 retains its program in internal Flash memory. This makes it "instant-on," a critical feature for boot logic, bus interfacing, and system control. * **Native 5V Operation:** The entire chip runs on a 5V core, making it perfect for interfacing with legacy TTL logic (like 74-series chips) without level shifters. * **Endurance:** Rated for 10,000 program/erase cycles.

1.2 Decoding the Part Number: -7 Speed and TQG100 Package

Understanding the suffix is vital for compatibility: * **XC95108:** Device type (108 Macrocells). * **-7:** **Speed Grade**. This indicates a **7.5 ns** pin-to-pin propagation delay. This is the *fastest* speed grade for this device. (Slower grades include -10, -15, -20). * **TQG:** Package Type. **Thin Quad Flat Pack (TQFP)** with the "G" indicating **Green (RoHS Compliant/Lead-Free)**. If you see just "TQ," it is the older leaded version. * **100:** Pin count (100 pins). * **C:** Temperature Grade (**Commercial**: 0°C to +70°C).

1.3 XC9500 vs. XC9500XL: The Critical Voltage Difference

> **WARNING:** Do not confuse the **XC95108** with the **XC95108XL**. > * **XC95108 (No Suffix):** **5V Core (VCCINT)**. > * **XC95108XL:** **3.3V Core (VCCINT)**. > > They are **NOT** drop-in replacements regarding power supply. Putting a 5V part in a 3.3V socket might work poorly or fail, but putting a 3.3V XL part in a 5V socket will destroy it. Always check the board's voltage regulator before replacing.

2.0 Key Technical Specifications

For a replacement part, specifications must match exactly to ensure timing and electrical compatibility.

2.1 Core Logic: Macrocells and Product Terms

* **Macrocells:** 108. These are the fundamental building blocks where your logic equations are stored. * **Usable Gates:** Approximately 2,400. * **Function Blocks:** 6 (Each containing 18 macrocells). * **Product Terms:** 5400. This high number allows for complex logic functions without cascading, which preserves speed.

2.2 Performance: 7.5ns Pin-to-Pin Delay

The **-7** speed grade is a high-performance variant. * **fCNT (Counter Frequency):** Up to 125 MHz. * **tPD (Propagation Delay):** 7.5 ns. * **System Clock:** Capable of supporting system clocks beyond 100 MHz, making it suitable for fast state machines and bus controllers.

2.3 Operating Conditions

* **Supply Voltage (VCCINT):** 5.0V ±5% (4.75V to 5.25V). * **Input Voltage:** 5V TTL Compatible. * **Output Voltage:** 5V CMOS/TTL Compatible.

3.0 Pinout and Package Details (TQFP-100)

The TQG100 is a surface-mount package. Proper soldering equipment (hot air or reflow) is required for replacement.

3.1 TQG100 Package Dimensions and Layout

* **Shape:** Square, 14mm x 14mm body. * **Pitch:** 0.5mm pin pitch. This fine pitch requires a steady hand for rework. * **Leads:** 100 pins total (25 per side).

3.2 Key Pin Functions: VCCINT, I/O, and JTAG

When troubleshooting, check these pins first: * **VCCINT:** Core power pins. Must be 5V. * **VCCIO:** I/O power pins. On the original XC9500 series, these are typically tied to 5V as well (unlike the XL/XV series which support multi-voltage I/O). * **GND:** Ground. * **JTAG (TMS, TCK, TDI, TDO):** Used for In-System Programming (ISP). * **GTS (Global Three-State):** Can float all outputs if asserted. * **GSR (Global Set/Reset):** Asynchronous reset for all flip-flops.

4.0 Programming and Maintenance Guide

The chip is blank when purchased. You must program it.

4.1 Required Software: Legacy Xilinx ISE 14.7

You **cannot** use the modern Xilinx Vivado software. The XC9500 family is too old. * **Software:** **Xilinx ISE Design Suite 14.7** (the "Windows 10" version or the standard version running on a Win7 VM). * **Module:** You specifically need the **iMPACT** tool within ISE to load the `.jed` (JEDEC) file into the CPLD.

4.2 JTAG Programming Hardware

* **Cable:** **Xilinx Platform Cable USB II** (or a high-quality clone). Older parallel port cables (Parallel Cable III/IV) work but require a legacy PC with a parallel port and Windows XP/7 (32-bit). * **Process:** Connect the cable to the board's JTAG header. Open iMPACT, scan the chain, assign the JEDEC file, and click "Program".

4.3 Obsolescence and Replacement Strategy

The **XC95108-7TQG100C** is a mature product. While AMD/Xilinx has supported this family for an incredibly long time, availability is tightening. * **Direct Replacement:** Always aim to buy the exact part number. The **-7** speed grade can replace slower -10 or -15 parts, but slower parts cannot replace a -7. * **Sourcing:** Since this is a legacy part, franchised distribution stock fluctuates. You often need to rely on specialized stocking distributors. Check AichipLink's inventory to find genuine stock.

In Conclusion

The XC95108-7TQG100C is a legend of the 5V era. Its robust design, predictable timing, and non-volatile memory make it irreplaceable in the legacy systems that still power much of our industrial infrastructure. Whether you are performing a critical repair or maintaining a fleet of aging hardware, understanding the specific voltage and speed requirements of this chip is the key to success.

If you need to source this hard-to-find component, don't risk your equipment on unverified suppliers. Contact AichipLink today for reliable, genuine legacy Xilinx parts.

 

 

 

 

 

Written by Jack Elliott from AIChipLink.

 

AIChipLink, one of the fastest-growing global independent electronic   components distributors in the world, offers millions of products from thousands of manufacturers, and many of our in-stock parts is available to ship same day.

 

We mainly source and distribute integrated circuit (IC) products of brands such as Broadcom, Microchip, Texas Instruments, Infineon, NXP, Analog Devices, Qualcomm, Intel, etc., which are widely used in communication & network, telecom, industrial control, new energy and automotive electronics. 

 

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