7.2.1.2 Input Considerations

Input signals must cross VIL(max) to be considered a logic LOW, and VIH(min) to be considered a logic HIGH. Do

not exceed the maximum input voltage range found in the Absolute Maximum Ratings.

Unused inputs must be terminated to either VCC or ground. The unused inputs can be directly terminated if the

input is completely unused, or they can be connected with a pull-up or pull-down resistor if the input will be used

sometimes, but not always. A pull-up resistor is used for a default state of HIGH, and a pull-down resistor is

used for a default state of LOW. The drive current of the controller, leakage current into the CDx4AC(T)164 (as

specified in the Electrical Characteristics), and the desired input transition rate limits the resistor size. A 10kΩ

resistor value is often used due to these factors.

The CDx4AC(T)164 has CMOS inputs and thus requires fast input transitions to operate correctly, as defined in

the Recommended Operating Conditions table. Slow input transitions can cause oscillations, additional power

consumption, and reduction in device reliability.

Refer to the Feature Description section for additional information regarding the inputs for this device.

7.2.1.3 Output Considerations

The ground voltage is used to produce the output LOW voltage. Sinking current into the output will increase the

output voltage as specified by the VOL specification in the Electrical Characteristics.

Unused outputs can be left floating. Do not connect outputs directly to VCC or ground.

Refer to the Feature Description section for additional information regarding the outputs for this device.

7.2.1.4 Application Curve

CLK

A

B

CLR

QA

QB

QC

QD

QE

QF

QG

QH

Clear

Clear

Figure 7-2. Application Timing Diagram

7.3 Power Supply Recommendations

The power supply can be any voltage between the minimum and maximum supply voltage rating located in

the Recommended Operating Conditions. Each VCC terminal should have a good bypass capacitor to prevent

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CD54AC164, CD74AC164, CD54ACT164, CD74ACT164

SCHS240D – NOVEMBER 1998 – REVISED OCTOBER 2024

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