A Dynamic Output Control (DOC) circuit is implemented, which, during the transition, initially lowers the output impedance to effectively drive the load and, subsequently, raises the impedance to reduce noise. Figure 1 shows typical VOL vs IOL and VOH vs IOH curves to illustrate the output impedance and drive capability of the circuit. At the beginning of the signal transition, the DOC circuit provides a maximum dynamic drive that is equivalent to a high-drive standard-output device. For more information, refer to the TI application reports,
AVC Logic Family Technology and Applications, literature number SCEA006, and
Dynamic Output Control (DOCTM
) Circuitry Technology and Applications, literature number SCEA009.
This 22-bit flip-flop is operational at 1.2-V to 3.6-V VCC, but is designed specifically for 1.65-V to 3.6-V VCC operation.
The 22 flip-flops of the SN74AVC16722 are edge-triggered D-type flip-flops with clock-enable (CLKEN\) input. On the positive transition of the clock (CLK) input, the device stores data into the flip-flops if CLKEN\ is low. If CLKEN\ is high, no data is stored.
A buffered output-enable (OE\) input places the 22 outputs in either a normal logic state (high or low) or the high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines significantly. 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.
This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs, preventing damaging current backflow through the device when it is powered down.
The SN74AVC16722 is characterized for operation from -40°C to 85°C.
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