8.1.3 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.

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

SN74ACT14-Q1 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.

8.1.4 Application Curves

2

3

2

4

2

3

Input ± 32 kHz

2

4

± 1 kHz

Figure 8-2. Application Timing Diagram

8.2 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

power disturbance. A 0.1μF capacitor is recommended for this device. It is acceptable to parallel multiple bypass

capacitors to reject different frequencies of noise. The 0.1μF and 1μF capacitors are commonly used in parallel.

The bypass capacitor should be installed as close to the power terminal as possible for best results.

8.3 Layout

8.3.1 Layout Guidelines

• Bypass capacitor placement

– Place near the positive supply terminal of the device

– Provide an electrically short ground return path

– Use wide traces to minimize impedance

– Keep the device, capacitors, and traces on the same side of the board whenever possible

• Signal trace geometry

– 8mil to 12mil trace width

– Lengths less than 12cm to minimize transmission line effects

– Avoid 90° corners for signal traces

– Use an unbroken ground plane below signal traces

– Flood fill areas around signal traces

– For traces longer than 12cm

• Use impedance controlled traces

• Source-terminate using a series damping resistor near the output

• Avoid branches; buffer signals that must branch separately

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