Just a guess, it's because the DDR075 is a half-value point for termination of the Address pins. So it's bypassed to remain a half-value.
Probably doesn't matter that much, as the entire DDR075 termination is just to reduce reflection, not as an reference point. By terminating to a half value, all the power lost in termination goes down by half.
What matters more is eliminating the DDR075 entirely, which I'm doing in my DDR2 design after a lot of research, in order to save power, space, and cost of the extra supply. The data lines are most critical and already terminated on chip. The Address isn't already terminated on-chip as it's not as critical. Several data sheets say the address termination isn't needed at all if you keep the path length under ~60 mm.
Just a guess, it's because the DDR075 is a half-value point for termination of the Address pins. So it's bypassed to remain a half-value.
Probably doesn't matter that much, as the entire DDR075 termination is just to reduce reflection, not as an reference point. By terminating to a half value, all the power lost in termination goes down by half.
What matters more is eliminating the DDR075 entirely, which I'm doing in my DDR2 design after a lot of research, in order to save power, space, and cost of the extra supply. The data lines are most critical and already terminated on chip. The Address isn't already terminated on-chip as it's not as critical. Several data sheets say the address termination isn't needed at all if you keep the path length under ~60 mm.
