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1

You choose a dielectric according to your other requirements. Other requirements include packing density of board accuracy/constancy of dielectric constant whether low loss is needed If you are making a high speed logic board, then generally loss and constancy are not too relevant. When you make a transmission line to get good propagation and control ...


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I'm very confused that dielectric constant should be selected high or low to design high-speed boards. I'll try and answer your question by considering inter-chip communication speeds on a circuit board using copper tracks. With a higher dielectric constant and a given PCB track width, the capacitance will be higher and this inevitably means that the ...


0

I think the hatched ground plane is more technological technique. It is used for better adhesion of layers on a flexible PCB or to reduce thermal dissipation in manual soldering. Sometimes a single ground plane cutout is used to optimizing impedance when a signal meets a discontinuity. It seems that impedance tunung with multiple cutouts is not a good and ...


3

So, i've finally assembled board with this design and DDR3 portion ended up working @ 333MHz. Although now i think traces is way too close to each other. W/3W rule must be kept. EDIT: Keep in mind that this design have very short(relatively) clock line. Some calibration algorithms on some systems may not work. EDIT: Yeah, my trace impedance is ~60Ohms. And ...


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The optoisolator has the pin 7 floating. It is common to put a bias resistor from that pin to ground, to help discharge the base charges, which turns off the transistor faster. Not all datasheets mention this. Try for example a 10k resistor there.


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