48-input×16-output crosspoint IC eliminates the need for multiplexer amps
Edited by Bill Travis
Mike Hess, Maxim Integrated Products, Sunnyvale, CA -- EDN, February 20, 2003
Crosspoint switches are ideal for use in video-security systems, which accept multiple camera inputs while providing playback and multiple loop-through to multiple monitors. To provide video loop-through or monitor outputs, these systems often require additional multiplexer amplifiers that can drive standard video loads. Thus, one or more external multiplexer amps often follow a crosspoint-matrix switch. As an alternative, you can employ a 32×16 nonblocking crosspoint-matrix switch, whose 16 2-to-1 multiplexers eliminate the need for extra multiplexer amps (Figure 1). The internal 2-to-1 multiplexers appear before the video-output buffers, which can each directly drive a standard video load. That configuration eliminates the need for external multiplexer amps and their associated cost, space requirement, and power consumption.
The MAX4358 IC is a fully buffered, 32-input×16-output nonblocking crosspoint switch that includes 16 additional buffered analog-video inputs (OSDFILL) intended for the insertion of OSD (on-screen-display) information. ("Nonblocking" means that the IC can route any input to any output.) The 16 fully buffered OSDFILL analog inputs are identical to the 32 inputs of the buffered crosspoint-switch matrix, so the 16 additional video inputs can implement a single-chip, 48-input×16-output crosspoint-switch matrix. The output buffers feature programmable gain (AV=1V/V or 2V/V). The programmability allows versatility in routing short video traces or driving video-transmission lines. Operating from dual ±3 to ±5V supplies or a single 5V supply, the device reduces power consumption by as much as 60% versus standard ±5V-only ICs.
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