SN74AXC8T245 8-Bit Dual-Supply Bus Transceivers

Texas Instruments' SN74AXC8T245 8-Bit dual-supply bus transceivers with configurable voltage translation and tri-state outputs

Texas Instruments' SN74AXC8T245 devices are 8-bit non-inverting bus transceivers that resolve voltage level mismatch between devices operating at the latest voltage nodes (0.7 V, 0.8 V, and 0.9 V) and devices operating at industry standard voltage nodes (1.8 V, 2.5 V, 3.3 V) and vice versa.

The devices operate by using two independent power-supply rails (V_CCA and V_CCB) that operate as low as 0.65 V. Data pins A1 through A8 are designed to track V_CCA, which accepts any supply voltage from 0.65 V to 3.6 V. Data pins B1 through B8 are designed to track V_CCB, which accepts any supply voltage from 0.65 V to 3.6 V.

The SN74AXC8T245 devices are designed for asynchronous communication between data buses. The devices transmit 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 (DIR1 and DIR2). The output-enable (OE) input is used to disable the outputs, so the buses are effectively isolated.

The SN74AXC8T245 devices are designed so the control pins (DIR and OE) are referenced to V_CCA.

These devices are fully specified for partial-power-down applications using I_off. The I_off circuitry disables the outputs when the device is powered down, inhibiting current backflow into the devices which prevents damage to the devices.

The V_CC isolation feature ensures that if either V_CC input supply is below 100 mV, all level shifter outputs are disabled and placed into a high-impedance state.

To ensure the high-impedance state of the level shifter I/Os during power up or power down, OE should be tied to V_CCA through a pull-up resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.