Driving video over twisted pair

Fully integrated into a single, 4 mm x 4 mm package, Analog Devices claims that its new AD8133 is the industry’s smallest triple differential line driver.

With the device, engineers needing to drive RGB (red-green-blue) signals over a twisted-pair cable can eliminate multiple-chip solutions, cutting costs by up to 50% and reducing board space by up to 75%.

Most critical to these applications is minimizing radiated electromagnetic interference (EMI). The AD8133’s internal common-mode feedback provides an output gain and phase balance of -60 dB at 50 MHz, suppressing EMI radiation and enabling the use of Category-5 unshielded twisted-pair (UTP) cable. Many applications benefit from the cost-savings of twisted-pair configurations over coaxial cable solutions.

The AD8133 driver accepts single-ended inputs and provides differential outputs; each amplifier has a fixed gain of 2 to compensate for the attenuation of line termination resistors. The AD8133 is specifically designed for RGB signals, but can be used for any type of analog signals or high-speed data transmission. The device is capable of driving either Cat-5 UTP cable or differential printed circuit board transmission lines with minimal signal degradation.

The outputs of the AD8133 can be set to a low voltage state for use with series diodes in line isolation applications, allowing differential multiplexing over the same twisted pair cable. The AD8133 driver can be used in conjunction with the AD8129 and AD8130 differential receivers.

Manufactured on ADI’s next-generation XFCB bipolar process, the AD8133 has a 225-MHz signal bandwidth and 1600-V/μsec slew rate. The output common-mode level is easily adjustable by applying a voltage to the Vocm input pin. The Vocm can also be used to transmit signals on the output common-mode voltages.

The AD8133 is priced at $2.59 per unit in 1,000-piece quantities and is in full production. The device operates over the industrial temperature range of -40 degrees Celsius to +85 degrees Celsius and is currently available in 24-pin LFCSP (lead frame chip scale packaging).

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