Microchip Technology

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  • Data and Transceiver Equalizer for Broadcast and Surveillance Cameras

  • Created: Jun 13, 2016

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Most of the commercial establishments are now equipped with surveillance cameras or Closed-circuit television (CCTV). It provides peace of mind to the owner of the establishment especially if its business enlists with different products and a number of employees. With this application, it requires data transmission and power over the same cable with external inductors. This data transmission over the cable with power may have possible issues on the attenuation of signal that can add up to the transmission line lengths issues. This will require equalizer that ensures the signal in the reception. This EQCO62R20.3 chipset is designed to work with several types of 75Ω coaxial cable. It supports up to 212m of cables at 1.25Gbps or up to 68m of cables at 6.25Gbps.

The designed circuit for this EQCO62R20.3 chipset is comprised of several external components that are provided as the recommended components so that this equalizer functions accordingly. The EQCO62R20.3 is single-coax chipset that can transmit and receive signals simultaneously on a single 75Ω coax cable. It is a high-speed receiver with an integrated low-speed transmitter, which is opposite to the EQCO62T20.3. It has auto adaptive characteristic that controls a multiple-pole analog filter to compensate for the attenuation of the cable. It has variable gain that compensate for low-frequency attenuation through the coax and variations in transmit amplitude. It is multi-speed at data rates from 1.25Gbps to 6.25Gbps with 8B/10B coding. Its output driver converts the output of the equalizer core to an LVDS-like signal and sends it onto a 100Ω differential transmission line. Both SDIp and SDIn inputs are terminated by 60Ω to VCC on-chip or internal output termination resistor. For each input, an external 15Ω resistor is required in series with the detection and adaption of signal (adds up to the internal 60Ω that results to balance with the coax characteristic impedance, which is 75Ω). The LFI requires external resistors for 2.5V and 3.3V input swing, that 3.9kΩ in the circuit it is probably for 2.5V input swing. The Ramp is 1.2 kΩ for 130mV transmit amplitude prevents crosstalk. The Rrise is 10kΩ for rise/fall time of 11ns. If no Ramp and Rrise are placed, the LF driver is disabled. The FB1, FB2, and L1 are recommended for CoaXPress but for the other applications, must be selected carefully for their RF-performance, thus performance can decrease significantly.

This design is not limited to surveillance cameras but also to the different application that uses single coax cable such as machine vision for semiconductor chips and display panel inspection system. It is applicable to traffic monitoring system and manufacturing monitoring. It is also applicable to high-speed inspection systems for food, panel, and bottling inspection.



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