LT1203/LT1205 OUUWUAPPLICATIS I FOR ATIO 4 VS = ±15V 3 RL = 150Ω RF = RG = 1.3k WORKSTATION 2 OUTPUT 1 R, B 0 G GAIN (dB) –1 –2 RGB MUX OUTPUT –3 –4 1 10 100 1000 FREQUENCY (MHz) LT1203/05 • F02a LT1203/05 • F04 Figure 2a. Workstation and RGB MUX OutputFigure 4. RGB MUX Frequency Response of Demonstration Board #041Input Expansion WORKSTATION OUTPUT The output impedance of the LT1203/LT1205 is typically 20Ω when enabled and 10MΩ when disabled or not selected. This high disabled output impedance allows the output of many LT1205s to be shorted together to form large crosspoint arrays. With their outputs shorted to- RGB MUX OUTPUT gether, shoot-through current is low because the “on” channel is disabled before the “off” channel is activated. Timing and Supply Current Waveforms LT1203/05 • F02b Figure 2b. RGB MUX Output Switched to Ground After One Pixel ENABLE 5V/DIV IC #1 ENABLE 5V/DIV IC #2 Demonstration Board VOUT A Demonstration Board (#041) of the RGB MUX in Figure 1V/DIV 1 has been fabricated and its layout is shown in Figure 3. The small-signal bandwidth of the RGB MUX is set by the IS bandwidth of the LT1260. The stray capacitance of the 10mA/DIV surface mount feedback resistors RF and RG restricts the – 3dB bandwidth to about 95MHz. The bandwidth can be LT1203/05 • AI04 improved by about 20% using the through-hole LT1260 and components. A frequency response plot in Figure 4 Four LT1205s are used in Figure 5 to form a 16-to-1 shows that the R, G, and B amplifiers have slightly multiplexer which is very space efficient and uses only six different frequency responses. The difference in the G SO packages. In this application 15 switches are turned off amplifier is due to different output trace routing to and only one is active. An attenuator is formed by the 15 feedback resistor R13. deselected switches and the active device which has an 9
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