SN74AXC4T245 Dual-Supply Bus Transceiver

Texas Instruments' SN74AXC4T245 4-bit, noninverting bus transceiver utilizes two individually-configurable power-supply rails and is operational with 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 transceiver device is compatible with a single-supply system.

The SN74AXC4T245 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 (1OE and 2OE) are used to disable the outputs so the buses are effectively isolated. The SN74AXC4T245 device is designed so the control pins (xDIR and xOE) are referenced to V_CCA. 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 pull-up resistor.

The device is fully specified for partial-power-down applications using the I_offcurrent. The I_off 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 V_CC isolation feature ensures that if either V_CCA or V_CCB is less than 100 mV, both I/O ports enter a high-impedance state by disabling their 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.