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Advantech COM-Express Carrier Board Design Guide Addendum Table 2-38 TV DAC Video filter components Component C1 C2 Value 6 pF 6 pF 150 Ω@ 100 MHz FB Tolerance Voltage/Current ± 20% ± 20% 16 V 16 V ± 25% 100 mA Type Ceramic Ceramic 2.11.3 Layout Guidelines 2.11.3.1 TV DAC routing The minimum spacing between each TV DAC signal is 40 mils, but 50 mils is preferred. A maximum amount of spacing should be used between each TV DAC signal as well as to all other toggling signals. This helps prevent crosstalk between the TV DAC signals and other signals. The routing for each TV DAC signal should also be matched and balanced. All TV DAC signals should be routed on the same layer, have a similar number of bends, the same number of vias, etc. All routing should be done with ground referencing as well. Figure 5-37 shows the TV DAC routing topology. Total length of each signal should be less than 12 inches. Intra-pair length difference should be less than 200 mils. Carrier board COM-Express Spacing >50 mils TV_ DAC _A Zo=50O Spacing >40 mils 150ohm Chipset TV_DAC _B Spacing >40 mils TV_ DAC _C 150ohm MAX =0.2" Zo=50O Spacing >50 mils 150ohm 150 ohm MAX =0.2" Zo=50O 150ohm 3.3V MAX =0.2" 150ohm Video Filter MAX=0.5‘ Zo=75 ohm Video Filter Connector MAX=0.5‘ Zo=75 ohm Video Filter 3.3V 75 ohm Coaxial Cable 3.3V MAX=0.5‘ Zo=75 ohm Figure 2-51 TV DAC Schematic 2.12 LPC COM-Express provides a LPC interface to some devices as Super I/O, FWH, TPM, and others. 2.12.1 Signal Description Table 2-39 shows COM-Express LPC signals. Table 2-39 LPC signals description Pin B4,5,6,7 Signal LPC_AD[0:3] I/O O Description LPC multiplexed address, command and data bus 57 TV
