Automotive four-bit dual-supply bus transceiver has configurable voltage-level shifting

This Texas Instruments 4-bit non-inverting bus transceiver uses two separate configurable power-supply rails. The A port is created to track VCCA. VCCA accepts any supply voltage from 1.02V to 3.6V. The B port is designed to track VCCB. VCCB accepts any supply voltage from 1.02V to 3.6V. The SN74AVC4T774-Q1 is optimised to operate with VCCA/VCCB set at 1.4V to 3.6V. It is operational with VCCA/VCCB as low as 1.02V. This provides for universal low-voltage bidirectional translation between any of the 1.2V, 1.5V, 1.8V, 2.5V, and 3.3V voltage nodes.

The device is intended 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 A and B ports is always active and must have a logic HIGH or LOW level applied to stop excess ICC and ICCZ.

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

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

The design of the VCC isolation feature places ports in the high-impedance state if either VCC input is at GND.

To place the device in a high-impedance state during power up or power down, tie OE to VCC through a pullup resistor; the driver's current-sinking capability determines the minimum value of the resistor.