Semiconductor manufacturers are always looking for the best interconnect solution to characterize the high-speed transceivers found on their FPGAs, ASICs and ASSPs. Typically, PCB-mount SMA connectors have been used to breakout the differential transmit and receive signals found in modern transceivers. Below is a Xilinx Spartan-6 FPGA SP623 Characterization Kit which features a number of PCB-mount SMA connectors.
This approach worked for decades. Transceiver counts per IC were low and PCB-mount SMA connectors could support data rates in the megabit and low gigabit per second range. As standard transceiver speeds have pushed past 10Gbps, high-speed PCB-mount SMA connectors were developed to support data rates up to 20 Gbps. However, another challenge came about due to Moore’s Law.
As ICs have gotten denser with ever-shrinking process nodes (90nm → 65nm → 45nm → 28nm → 20nm → 16nm), ASIC, FPGA and ASSP manufacturers have increased transceiver counts on their high-speed semiconductor solutions. As an example, Xilinx plans up to 76 transceivers on their Zynq® UltraScale+™ MPSoCs and up to 128 transceivers on their Virtex® UltraScale+™ FPGAs.
Characterization boards for these devices would require hundreds of PCB-mount SMA connectors. This approach proves impractical due to PCB size and cost constraints. Additionally, overly complex PCB layouts are required to support the dozens of discrete SMA connectors. There has to be a better way, right?
The Samtec Bulls Eye® Test Point System
Fortunately, Samtec answered this challenge with our Bulls Eye® Test Point System. Bulls Eye was designed as an SMA-replacement technology for test and measurement systems. It offers reduced board space and trace lengths, higher performance and lower cost compared to traditional PCB-mount SMA connectors. The high density array designs of the Bulls Eye system provide up to 4x the high bandwidth signals in the same real estate as SMA connectors. The system is available in single or multi-port designs, or as a high-density ganged connector.
Bulls Eye® has found an additional home in FPGA characterization, evaluation and development boards. Samtec and Xilinx have worked together to simplify the design and reduce the PCB space on multiple generations of FPGA boards. Xilinx uses Bulls Eye® on the following kits:
- Virtex-6 FPGA ML628 Characterization Kit
- Xilinx Kintex-7 FPGA KC724 Characterization Kit
- Xilinx Virtex-7 FPGA VC7203 Characterization Kit
- Xilinx Virtex-7 FPGA VC7215 Characterization Kit
- Xilinx Virtex-7 FPGA VC7222 Characterization Kit
- Xilinx Kintex UltraScale FPGA KCU1250 Characterization Kit
- Xilinx Virtex UltraScale FPGA VCU1287 Characterization Kit
- Xilinx Virtex UltraScale FPGA VCU108 Evaluation Kit
- Xilinx Virtex UltraScale FPGA VCU110 Development Kit
Below is a Xilinx Kintex UltraScale FPGA KCU1250 Characterization Kit with eight Bulls Eye pads.
More recently, Xilinx has announced the availability of the first member of their UltraScale+ portfolio — the Zynq® UltraScale+™ MPSoC. This platform contains three types of high-speed transceivers: a 6 Gbps GTR transceiver, a midrange 16.3 Gbps GTH transceiver and the high performance 32.75Gbps GTY transceivers. Xilinx has developed a video demonstrating the performance and signal quality of the transceivers.
Throughout the video, the Samtec’s Bulls Eye® Test Point System is shown deliver data at rates greater than 16Gbps.
Take special note around the 2:45 mark in the video. You’ll notice a second generation Bulls Eye cable assembly. Samtec developed this to offer increased performance (the cable offers phase matching of +/-1ps). This generation of the system offers increased robustness, repeatability and flex- life over previous generations of Bulls Eye.