LT6553 UTYPICAL APPLICATIO S A fourth signal trace is provided at the bottom of the within the input and output common mode range of the DC714 demo board with dimensions identical to the part. On a 9V single supply, the input would sit at 2.2V DC, combined input and output of the other channels. This and the output would sit at 4.4V. trace can be used for calibrating the effects of electrical Due to the 220µF coupling cap at the output, the only delay and impedance mismatching and is not necessary additional power dissipation due to the positive output in an end-user application. Several jumpers and addi- voltage is through the feedback and gain resistors. Since tional connectors are also included to allow for testing of those resistors are approximately 740Ω in series, the the enable feature and single supply operation. additional quiescent current is only 6mA per channel. Single Supply RGB Buffer Demo BoardRGB Video Selector/Cable Driver The DC743A Demo Board uses the LT6553 in a single A video multiplexer can be implemented using the EN pins supply application with AC coupled inputs and outputs. It of parallel LT6553s as shown in Figure 3. In this applica- is nearly identical to the DC714 RGB Buffer Demo Board tion, all outputs are connected together and one LT6553 is but has the additional components required for AC cou- switched on while the other is switched off. A fast inverter pling and setting a DC bias point at the input. A schematic provides a complementary signal to ensure that only one of a single channel is shown in Figure 2. AC performance set of R, G and B channels is buffered at any time. As of the LT6553 in the single supply application as shown is shown, the outputs are connected before the 75Ω series nearly identical to performance with dual supplies. termination resistors in order to reduce any DC attenua- The 6.8k and 2.2k bias resistors at the input set up a tion that may result from the non-infinite output imped- nominal DC voltage at the input that keeps a video signal ance of the disabled LT6553. 7V TO 12V 6.8k 22µF* 220µF** INPUT 75Ω + IN OUT 1/3 LT6553 AGND 80.6Ω 2.2k 75Ω * AVX 12066D226MAT ** SANYO 6TPB220ML 6553 F02 Figure 2. Single Supply Configuration, One Channel Shown 6553f 10