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High Speed Amplifiers for Video Applications Pt 3 Slide 2

Let’s talk about the MUX crosstalk specs a little bit. One of the more important set of specs for the video MUXs is the crosstalk specification. There are two things which are important. One, how well is the selected input isolated from the unselected ones? This is called crosstalk. Number two is how well is the output isolated from any signal on the input when the device is in shutdown or disable mode, called off-isolation, different from crosstalk. Both of these are shown as a function of frequency for the LMH6574 in this case. As you might expect, there is strong frequency dependence due to parasitic coupling for both curves. Both crosstalk and off-isolation for the LMH6572 and the 6574 are among the industry’s best. Focusing on the curve to the right, you will notice that there are two plots. The curve labeled shutdown affords more isolation. The 6574 was designed for flexibility in trading off between sleep mode power savings, popless output, and fast action. Putting a device in shutdown offers more power saving, more isolation but at the expense of about 400 millivolts maximum output spike. The enable/disable function minimizes output glitch at the expense of more sleep mode power and less isolation, as can be seen, on the right-hand side graph.

PTM Published on: 2011-11-21