SN74AXCH4T245

The SN74AXCH4T245 is a four-bit noninverting bus transceiver that uses two individually configurable power-supply rails. The device is operational with both V_CCA and V_CCB supplies as low as 0.65 V. The A port is designed to track V_CCA, which accepts any supply voltage from 0.65 V to 3.6 V. The B port is designed to track V_CCB, which accepts any supply voltage from 0.65 V to 3.6 V. The SN74AXCH4T245 device is compatible with a single-supply system.

The SN74AXCH4T245 device is designed for asynchronous communication between data buses and transmits data from the A bus to the B bus or from the B bus to the A bus, depending on the logic level of the direction-control inputs (1DIR and 2DIR). The output-enable inputs (1OE and 2OE) are used to disable the outputs so the buses are effectively isolated. All control pins (xDIR and xOE) are referenced to V_CCA.

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. If a supply is present for V_CCA or V_CCB, the bus-hold circuitry always remains active on the A or B inputs respectively, independent of the state of the direction control or output enable pins.

To ensure the high-impedance state of the level shifter I/Os during power up or power down, the xOE pins should be tied to V_CCA through a pullup resistor.

This device is fully specified for partial-power-down applications using the I_off current. The I_off protection circuitry ensures that no excessive current is drawn from or sourced into an input, output, or combined I/O that is biased to a specific voltage while the device is powered down.

The V_CC isolation feature ensures that if either V_CCA or V_CCB is less than 100 mV, all I/O ports enter a high-impedance state by disabling the outputs.

Glitch-free power supply sequencing allows either supply rail to be powered on or off in any order while providing robust power sequencing performance.