3.3-V 20-Bit Flip-Flop With 3-State Outputs

This 20-bit flip-flop is designed for low-voltage 1.65-V to 3.6-V VCC operation.

The 20 flip-flops of the SN74ALVCH162721 are edge-triggered D-type flip-flops with qualified clock storage. On the positive transition of the clock (CLK) input, the device provides true data at the Q outputs if the clock-enable (CLKEN)\ input is low. If CLKEN\ is high, no data is stored.

A buffered output-enable (OE)\ input places the 20 outputs in either a normal logic state (high or low level) or the 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 interface or pullup components. OE\ does not affect the internal operation of the flip-flops. Old 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, 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.

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

The outputs, which are designed to sink up to 12 mA, include equivalent 26- resistors to reduce overshoot and undershoot.

The SN74ALVCH162721 is characterized for operation from –40°C to 85°C.