The SN74AVCH8T245 is an 8-bit noninverting bus transceiver that uses two separate
configurable power-supply rails. The A port is designed to track VCCA, which
accepts any supply voltage from 1.2 V to 3.6 V. The B port is designed to track
VCCB, which also accepts any supply voltage from 1.2 V to 3.6 V. This allows
for universal low-voltage bidirectional translation between any of the 1.2-V, 1.5-V, 1.8-V, 2.5-V,
and 3.3-V voltage nodes.
The SN74AVCH8T245 is designed for asynchronous communication between data buses. The
device transmits data from either the A bus to the B bus, or from the B bus to the A bus, depending
on the logic level at the direction-control (DIR) input. The output-enable
(OE) input can be used to disable the outputs so the buses are effectively
The SN74AVCH8T245 is designed so that the control pins (DIR and
OE) are referenced to VCCA.
Active bus-hold circuitry holds unused or undriven inputs at a valid logic state. Use of
pullup or pulldown resistors with the bus-hold circuitry is not recommended.
This device is fully specified for partial-power-down applications using
Ioff. The Ioff circuitry disables the outputs,
preventing damaging current backflow through the device.
The VCC isolation feature ensures that if either
VCCA or VCCB is at GND, then the outputs are in the
high-impedance state. The bus-hold circuitry on the powered-up side always stays active.
The SN74AVCH8T245 solution is compatible with a single-supply system and can be replaced
later with a 245 function, with minimal printed circuit board redesign.
To ensure the high-impedance state during power up or power down,
OE shall be tied to VCCA through a pullup resistor;
the minimum value of the resistor is determined by the current-sinking capability of the
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