The Texas Instruments SN74AXCH1T45 is a single-bit non-inverting bus transceiver that utilises 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. Further, the device is compatible with a single-supply system.
The DIR pin determines the direction of signal propagation. With the DIR pin configured HIGH, translation is from Port A to Port B. With DIR configured LOW, translation is from Port B to Port A. The DIR pin is referenced to VCCA, meaning that its logic-high and logic-low thresholds track with VCCA.
Active bus-hold circuitry retains 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 VCCA or VCCB, the bus-hold circuitry constantly remains active on the A or B inputs respectively, independent of the state of the direction control pin.
This device is completely specified for partial-power-down applications using the Ioff current. The Ioff protection circuitry assures that no excessive current is taken from or to an input, output, or combined I/O that is biased to a particular voltage while the device is powered down.
The VCC isolation feature assures that if either VCCA or VCCB is less than 100mV, both I/O ports enter a high-impedance state by disabling their outputs.
Glitch-free power supply sequencing enables either supply rail to be powered on or off in any order whilst giving robust power sequencing performance.