4-bit dual-supply bus transceiver

The SN74AXC4T245 is a four-bit noninverting bus transceiver that uses two individually configurable power-supply rails. The device is operational with both VCCA and VCCB supplies as low as 0.65V. The A port is designed to track VCCA, which accepts any supply voltage from 0.65V to 3.6V. The B port is designed to track VCCB, which also accepts any supply voltage from 0.65V to 3.6V. Additionally the SN74AXC4T245 is compatible with a single-supply system.

The SN74AXC4T245 device is designed for asynchronous communication between data buses. The device 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 (1 OE and 2 OE) are used to disable the outputs so the buses are effectively isolated. The SN74AXC4T245 device is designed so the control pins (xDIR and x OE) are referenced to VCCA.

To put the level shifter I/Os in the high-impedance state during power up or power down, tie the xOE pins to VCCA through a pullup resistor.

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

The design of the VCC isolation feature allows both I/O ports to enter a high-impedance state by disabling their outputs if either VCCA or VCCB is less than 100mV.

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