SN74AVCH4T245-EP

This 4-bit noninverting bus transceiver uses two separate configurable power-supply rails. The A port is designed to track V_CCA. V_CCA accepts any supply voltage from 1.2 V to 3.6 V. The B port is designed to track V_CCB. V_CCB accepts any supply voltage from 1.2 V to 3.6 V. The SN74AVCH4T245 is optimized to operate with V_CCA/V_CCB set at 1.4 V to 3.6 V. It is operational with V_CCA/V_CCB as low as 1.2 V. This allows for universal low-voltage bidirectional translation between any of the 1.2-V, 1.5-V, 1.8-V, 2.5-V, and 3.3-V voltage nodes.

The SN74AVCH4T245 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 or the A-port outputs or place both output ports into the high-impedance mode. 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 is always active and must have a logic HIGH or LOW level applied to prevent excess I_CC and I_CCZ.

The SN74AVCH4T245 is designed so that the control pins (1DIR, 2DIR, 1OE, and 2OE) are supplied by V_CCA.

This device is fully specified for partial-power-down applications using I_off. The I_off circuitry disables the outputs, preventing damaging current backflow through the device when it is powered down.

The V_CC isolation feature ensures that if either V_CC input is at GND, then both ports are in the high-impedance state. The bus-hold circuitry on the powered-up side always stays 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.

To ensure the high-impedance state during power up or power down, OE should be tied to V_CC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.