2. Ensure the capacitive load at the output is ≤ 50pF. This is not a hard limit; by design, however, it will

optimize performance. This can be accomplished by providing short, appropriately sized traces from the

SN74LVC166A to one or more of the receiving devices.

3. Ensure the resistive load at the output is larger than (VCC / IO(max))Ω. Doing this will prevent the maximum

output current from the Absolute Maximum Ratings from being violated. Most CMOS inputs have a resistive

load measured in MΩ; much larger than the minimum calculated previously.

4. Thermal issues are rarely a concern for logic gates; the power consumption and thermal increase, however,

can be calculated using the steps provided in the application report, CMOS Power Consumption and Cpd

Calculation.

8.2.3 Application Curves

SH/LD

CLK

DATA[A:H]

QH

CLR

0x00

0x11

0x00

Figure 8-2. Application Timing Diagram

8.3 Power Supply Recommendations

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

Recommended Operating Conditions.

During startup, the power supply should ramp within the provided power-up ramp rate range in the

Recommended Operating Conditions table.

Each VCC terminal should have a good bypass capacitor to prevent power disturbance. For the SN74LVC166A,

a 0.1μF bypass capacitor is recommended. To reject different frequencies of noise, use multiple bypass

capacitors in parallel. Capacitors with values of 0.1μF and 1μF are commonly used in parallel.

8.4 Layout

8.4.1 Layout Guidelines

When using multiple-input and multiple-channel logic devices, inputs must never be left floating. In many cases,

functions or parts of functions of digital logic devices are unused; for example, when only two inputs of a

triple-input AND gate are used or only 3 of the 4 buffer gates are used. Such unused input pins must not be left

unconnected because the undefined voltages at the outside connections result in undefined operational states.

All unused inputs of digital logic devices must be connected to a logic high or logic low voltage, as defined by the

input voltage specifications, to prevent them from floating. The logic level that must be applied to any particular

unused input depends on the function of the device. Generally, the inputs are tied to GND or VCC, whichever

makes more sense for the logic function or is more convenient.

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SN74LVC166A

SCLSA15 – MAY 2024

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