The EM74LVC8T245; EM74LVCH8T245 is an 8-bit dual supply translating transceivers with 3-state  outputs that enable bidirectional level translation. They feature two data input-output ports (pins  An and Bn), a direction control input (DIR), an output enable input (OE) and dual supply pins (VCC(A) and VCC(B)). Both VCC(A) and VCC(B) can be supplied at any voltage between 1.2 V and 5.5 V making  the device suitable for translating between any of the low voltage nodes (1.2 V, 1.5 V, 1.8 V, 2.5  V, 3.3 V and 5.0 V). Pins An, OE and DIR are referenced to VCC(A) and pins Bn are referenced to  VCC(B). A HIGH on DIR allows transmission from An to Bn and a LOW on DIR allows transmission  from Bn to An. The output enable input (OE) can be used to disable the outputs so the buses are  effectively isolated.  

The devices are fully specified for partial power-down applications using IOFF. The IOFF circuitry  disables the output, preventing any damaging backflow current through the device when it is  powered down. In suspend mode when either VCC(A) or VCC(B) are at GND level, both A port and B  port are in the high-impedance OFF-state.  

Active bus hold circuitry in the EM74LVCH8T245 holds unused or floating data inputs at a valid  logic level.