The SN74LVC166A can drive a load with a total capacitance less than or equal to 50pF while still meeting all of

the data sheet specifications. Larger capacitive loads can be applied; however, it is not recommended to exceed

50pF.

The SN74LVC166A can drive a load with total resistance described by RL ≥ VO / IO, with the output voltage and

current defined in the Electrical Characteristics table with VOH and VOL. When outputting in the HIGH state, the

output voltage in the equation is defined as the difference between the measured output voltage and the supply

voltage at the VCC pin.

Total power consumption can be calculated using the information provided in CMOS Power Consumption and

Cpd Calculation.

Thermal increase can be calculated using the information provided in Thermal Characteristics of Standard Linear

and Logic (SLL) Packages and Devices.

CAUTION

The maximum junction temperature, TJ(max) listed in the Absolute Maximum Ratings, is an additional

limitation to prevent damage to the device. Do not violate any values listed in the Absolute Maximum

Ratings. These limits are provided to prevent damage to the device.

8.2.1.2 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 SN74LVC166A (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 SN74LVC166A 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.

8.2.1.3 Output Considerations

The positive supply voltage is used to produce the output HIGH voltage. Drawing current from the output will

decrease the output voltage as specified by the VOH specification in the Electrical Characteristics. 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.

Push-pull outputs that could be in opposite states, even for a very short time period, should never be connected

directly together. This can cause excessive current and damage to the device.

Two channels within the same device with the same input signals can be connected in parallel for additional

output drive strength.

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.

8.2.2 Detailed Design Procedure

1. Add a decoupling capacitor from VCC to GND. The capacitor needs to be placed physically close to the

device and electrically close to both the VCC and GND pins. An example layout is shown in the Layout

section.

SN74LVC166A

SCLSA15 – MAY 2024

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