The SN74LVCH8T245 is an 8-bit noninverting bus transceiver that uses two separate configurable power-supply rails. The A port is designed to track VCCA, which accepts any supply voltage from 1.65 V to 5.5 V. The B port is designed to track VCCB, which also accepts any supply voltage from 1.65 V to 5.5 V. This allows for universal low-voltage bidirectional translation between any of the 1.8-V, 2.5-V, 3.3-V, and 5.5-V voltage nodes.The SN74LVCH8T245 is designed for asynchronous communication between two data buses. The logic levels of the direction-control (DIR) input and the output-enable (OE) input activate either the B-port outputs, the A-port outputs, or place both output ports into a high-impedance state. The device transmits data from the A bus to the B bus when the B-port outputs are activated, and from the B bus to the A bus when the A-port outputs are activated. The input circuitry on both A and B ports are always active.Active bus-hold circuitry holds unused or undriven inputs at a valid logic state. Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended. This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs, preventing damaging current backflow through the device. The VCC isolation feature ensures that if either VCCA or VCCB is at GND, then the outputs are in the high-impedance state. To ensure the high-impedance state during power up or power down, OE should be tied to VCCA through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.The SN74LVCH8T245 is designed so that the control pins (DIR and OE) are referenced to VCCA.
