This 16-bit noninverting bus transceiver uses two separate configurable power-supply
rails. The A port is designed to track VCCA. VCCA
accepts any supply voltage from 1.65 V to 5.5 V. The B port is designed to track
VCCB. VCCB accepts any supply voltage from 1.65 V to
5.5 V. This allows for universal low-voltage bidirectional translation between any of the 1.8-V,
2.5-V, 3.3-V, and 5-V voltage nodes.
The SN74LVCH16T245 device control pins (1DIR, 2DIR, 1OE, and
2OE) are supplied by VCCA.
The SN74LVCH16T245 device is designed 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 both A and B ports is always active and must have a logic
HIGH or LOW level applied to prevent excess ICC and
Active bus-hold circuitry holds unused or undriven data inputs at a valid logic state.
Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended. The bus-hold
circuitry on the powered-up side always stays active.
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 when it is powered down.
The VCC isolation feature ensures that if either
VCC input is at GND, then all outputs are in the high-impedance state. To
ensure the high-impedance state during power up or power down, OE should be
tied to VCC through a pullup resistor; the minimum value of the resistor is
determined by the current-sinking capability of the driver.
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