TXS0104E: Input Low logic Level with Buffer

The listed V_IL value is not really a requirement; it is listed only because V_OL depends on it: the output voltage is the input voltage plus the voltage drop over the switch.

What is the original purpose of R160? If there is a long trace between U20 and U3, then it should be no larger than the characteristic impedance of the trace, which is probably about 100 Ω.

Hi

Track length between U20 and U3 is around around 100 mm.

Design was taken form old referecne , not sure why R160 used , to limi the current of SN74LVC1G240DBVR or else. That why asking can we replace the R160 with 0 ohm or some low like 100-300ohm.

so what is the VIL requiremnt of TXS0104EPWR.

also why its go to 0.480V low level(See figure given earlier), ideally U3 has interal pull up of (10K), so low level should be 3.3V/(1K+10) * 1K =0.3V but still going out of spec.

Please note that the current from both pull-up resistors flows through R160.

I cannot tell you what the original circuit designer thought. But I suspect that the resistor was intended to prevent overshoots due to the LVC's fast output edges. 100 Ω should work fine. (To have 0 Ω for DC signals but prevent fast edges, replace it with a ferrite bead. But that is probably too expensive.)

Strictly speaking, the TXS does not have a V_IL requirement. If you increase the input voltage, the output voltage increases by the same amount. Only at input voltages higher than about V_CCA − 1 V does the switch close.

so if TXS does not have VIL requirement than how it will indentified high and low level of incoming signal. in my curretn case high level is 3.3V an dlow level is araound 0.48V , so TXS can switch properly.

is there any reliability issue.

As I said, voltages higher than about V_CCA − 1 V close the switch and result in a high output.

The TXS does not "identify" low signals; when the switch is on, the output voltage is the input voltage plus a small offset.