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SN74HCS596-Q1

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SCLS805 – JUNE 2020

Product Folder Links: SN74HCS596-Q1

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Copyright © 2020, Texas Instruments Incorporated

Typical Application (continued)

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.

9.2.1.2 Input Considerations

Input signals must cross Vt-(min) to be considered a logic LOW, and Vt+(max) 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. These 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 is to 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 resistor size is limited by drive current of the controller, leakage current into the

SN74HCS596-Q1, as specified in the Electrical Characteristics, and the desired input transition rate. A 10-kΩ

resistor value is often used due to these factors.

The SN74HCS596-Q1 has no input signal transition rate requirements because it has Schmitt-trigger inputs.

Another benefit to having Schmitt-trigger inputs is the ability to reject noise. Noise with a large enough amplitude

can still cause issues. To know how much noise is too much, please refer to the ΔVT(min) in the Electrical

Characteristics. This hysteresis value will provide the peak-to-peak limit.

Unlike what happens with standard CMOS inputs, Schmitt-trigger inputs can be held at any valid value without

causing huge increases in power consumption. The typical additional current caused by holding an input at a

value other than VCC or ground is plotted in the Typical Characteristics.

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

9.2.1.3 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.

Open-drain outputs can be directly connected together to produce a wired-AND. This is possible because the

outputs cannot source current, and thus can never be in bus-contention.

Unused outputs can be left floating.

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

9.2.1.4 Timing Considerations

The SN74HCS596-Q1 is a clocked device. As such, it requires special timing considerations to ensure normal

operation.

Primary timing factors to consider:

•

Maximum clock frequency: the maximum operating clock frequency defined in Timing Characteristics is the

maximum frequency at which the device is guaranteed to function. This value refers specifically to the

triggering waveform, measuring from one trigger level to the next.

•

Pulse duration: ensure that the triggering event duration is larger than the minimum pulse duration, as defined

in the Timing Characteristics.

•

Setup time: ensure that the data has changed at least one setup time prior to the triggering event, as defined

in the Timing Characteristics.

•

Hold time: ensure that the data remains in the desired state at least one hold time after the triggering event,

as defined in the Timing Characteristics.

9.2.2 Detailed Design Procedure

1. Recommended Input Conditions: