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.