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 (DOC) Circuitry Technology and Applications, literature number SCEA009.
This 18-bit universal bus driver 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.
Data flow from A to Y is controlled by the output-enable (OE)\ input. The device operates in the transparent mode when the latch-enable (LE)\ input is low. The A data is latched if the clock (CLK) input is held at a high or low logic level. If LE\ is high, the A data is stored in the latch/flip-flop on the low-to-high transition of CLK. When OE\ is high, 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.
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