8-bit dual-supply bus transceiver with configurable voltage translation and 3-state outputs

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 1.65V to 5.5V. The B port is designed to track VCCB, which also

accepts any supply voltage from 1.65V to 5.5V. This allows for universal low-voltage

bidirectional translation between any of the 1.8V, 2.5V, 3.3V, and 5.5V 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 is designed so that if either VCCA or VCCB

is at GND, then the outputs are in the high-impedance state. To put the device in

the high-impedance state during power up or power down, tie OE

to VCCA through a pullup resistor; the current-sinking capability of the

driver determines the minimum value of the resistor.

The SN74LVCH8T245 is designed so that the control pins (DIR and OE) are referenced to VCCA.