TXB0104-Q1: The difference between SN series and TXB series level converters

The TXB chips are auto-bidirectional, i.e., the input and output buffers on both sides are always active. To make this work, the output buffers are very weak to allow the other devices to override the voltage. This implies that the TXB cannot be used as a buffer, and does not work with strong pull-up/-down resistors or high capacitive loads (such as long traces/connectors/cables).

The SN translators work similar to basic '245 transceivers, i.e., they have high-impedance inputs and low-impedance outputs (in the configured direction), and work as buffers.

In general, for unidirectional signals, you should use unidirectional translators, i.e., TXU0104-Q1/TXU0204-Q1/TXU0304-Q1.