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The SN74LVTH16543 is a 16–bit registered transceiver designed for low–voltage (3.3–V) V_CC operation, but with the capability to provide a TTL interface to a 5–V system environment. This device can be used as two 8–bit transceivers or one 16–bit transceiver. Separate latch–enable (LEAB or LEBA) and output–enable (OEAB or OEBA) inputs are provided for each register to permit independent control in either direction of data flow.

The A–to–B enable (CEAB) input must be low to enter data from A or to output data from B. If CEAB is low and LEAB is low, the A–to–B latches are transparent; a subsequent low–to–high transition of LEAB puts the A latches in the storage mode. With CEAB and OEAB both low, the 3–state B outputs are active and reflect the data present at the output of the A latches. Data flow from B to A is similar, but requires using the CEBA, LEBA, and OEBA inputs.

Active bus–hold circuitry is provided to hold unused or floating data inputs at a valid logic level.

When V_CC is between 0 and 1.5 V, the device is in the high–impedance state during power up or power down. However, to ensure the high–impedance state above 1.5 V, OE should be tied to V_CC through a pullup resistor; the minimum value of the resistor is determined by the current–sinking capability of the driver.

This device is fully specified for hot–insertion applications using I_off and power–up 3–state. The I_off circuitry disables the outputs, preventing damaging current backflow through the device when it is powered down. The power–up 3–state circuitry places the outputs in the high–impedance state during power up and power down, which prevents driver conflict.