These 8-bit flip-flops with 3-state outputs are designed specifically for driving highly capacitive or relatively low-impedance loads. They are particularly suitable for implementing buffer registers, I/O ports, bidirectional bus drivers, and working registers.
The eight flip-flops are edge-triggered D-type flip-flops. On the positive transition of the clock (CLK), the Q\ outputs are set to the complement of the logic levels set up at the data (D) inputs.
A buffered output-enable () input can be used to place the eight outputs in either a normal logic state (high or low logic levels) or a high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines significantly. The high-impedance state and increased drive provide the capability to drive bus lines without need for interface or pullup components.
does not affect the internal operations of the flip-flop. Previously stored data can be retained or new data can be entered while the outputs are in the high-impedance state.
To ensure the high-impedance state during power up or power down, 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.
The SN54ABT534 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ABT534A is characterized for operation from -40°C to 85°C.
