The 'LVTH16543 devices are 16-bit registered transceivers designed for low-voltage (3.3-V) VCC operation, but with the capability to provide a TTL interface to a 5-V system environment. These devices 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 VCC is between 0 and 1.5 V, the devices are 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 VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
These devices are fully specified for hot-insertion applications using Ioff and power-up 3-state. The Ioff circuitry disables the outputs, preventing damaging current backflow through the devices when they are 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.
The SN54LVTH16543 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74LVTH16543 is characterized for operation from -40°C to 85°C.
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