SCES642L December 2007 – November 2024 TXS0108E
PRODUCTION DATA
TI recommends careful PCB layout practices with short PCB trace lengths to avoid excessive capacitive loading and so that proper one-shot triggering takes place. PCB signal trace-lengths should be kept short enough such that the round trip delay of any reflection is less than the one-shot duration. This improves signal integrity by allowing any reflection to see a low impedance at the driver. The one-shot circuits have been designed to stay on for approximately 30ns. The maximum capacitance of the lumped load that can be driven also depends directly on the one-shot duration. With very heavy capacitive loads, the one-shot can time-out before the signal is driven fully to the positive rail. The one-shot duration has been set to best optimize trade-offs between dynamic ICC, load driving capability, and maximum bit-rate considerations. Both PCB trace length and connectors add to the capacitance of the TXS0108E output. Therefore, TI recommends that this lumped-load capacitance is considered to avoid one-shot retriggering, bus contention, output signal oscillations, or other adverse system-level affects.