20-Bit Bus-Interface D-Type Latches With 3-State Outputs

These 20-bit latches feature 3-state outputs 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 'ABT16841 can be used as two 10-bit latches or one 20-bit latch. The 20 transparent D-type latches provide true data at the outputs. While the latch-enable (1LE or 2LE) input is high, the Q outputs of the corresponding 10-bit latch follow the D inputs. When LE is taken low, the Q outputs are latched at the levels set up at the D inputs.

A buffered output-enable (1OE\ or 2OE\) input can be used to place the outputs of the corresponding 10-bit latch 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 output-enable input does not affect the internal operation of the latches. Old data can be retained or new data can be entered while the outputs are in the high-impedance state.

When VCC is between 0 and 2.1 V, the device is in the high-impedance state during power up or power down. However, to ensure the high-impedance state above 2.1 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.

The SN54ABT16841 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ABT16841 is characterized for operation from -40°C to 85°C.