TXB0108 and length of cables

de pan said:

 I am using TXB0108 in my design.Eight LVTTL signals are Transformed by a TXB0108 from 3.3V to 5v frist,then carried by 8 cables(the other end of cables is Suspended).The issue is that the signals are ok when the length of cables is 0.5m,but he signals are bad when the length of cables over 1m.TXB0108  has very  ow dc drive strength,is it the reasen?Or the load driving is over 70pF max?Or other reasens esle?

With the low voltages, it sounds like you are running in to the problems USB has with cable length.  The longer the cable, the more like an antena it becomes and the more interference, impedance, etc from being that long. Coax impedance range from 68 to 85 Ohms, 2 wire with gap can get 300 Ohms or more impedance and drastically change the signal even if you use braided shielding over the wires.  I do not know what the end result is for the 8 separate lines, one workaround you might want to look in to is pairing each with a ground to see if that limits or lowers the signal loss as that was a workaround for longer cables in the early days of PCs where high amounts of 8 bit data would be carried from one room to another and would need no data corruption.  That would mean 16 separate wires grouped as 8 pairs with the pairs wrapped together.  Standard Ethernet ( CAT 5 UTP colored Blue ) typically has that and 2 sections of 1M in length are not that expensive.

Sometimes the solutions have already been found in other aplications,

hope this helps.