8 Detailed Description

8.1 Overview

The SN74HCS541-Q1 contains eight buffers with 3-state outputs and Schmitt-trigger inputs. The active low

output enable pins (OE1, OE2) control all eight channels, and are configured such that both must be low for the

outputs to be active.

When the outputs are enabled, the outputs are actively driving low or high.

When the outputs are disabled, the outputs are set into the high-impedance state.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Balanced CMOS 3-State Outputs

This device includes balanced CMOS 3-State outputs. The three states that these outputs can be in are driving

high, driving low, and high impedance. The term "balanced" indicates that the device can sink and source similar

currents. The drive capability of this device may create fast edges into light loads so routing and load conditions

should be considered to prevent ringing. Additionally, the outputs of this device are capable of driving larger

currents than the device can sustain without being damaged. It is important for the output power of the device

to be limited to avoid damage due to overcurrent. The electrical and thermal limits defined in the Absolute

Maximum Ratings must be followed at all times.

When placed into the high-impedance mode, the output will neither source nor sink current, with the exception of

minor leakage current as defined in the Electrical Characteristics table. In the high-impedance state, the output

voltage is not controlled by the device and is dependent on external factors. If no other drivers are connected

to the node, then this is known as a floating node and the voltage is unknown. A pull-up or pull-down resistor

can be connected to the output to provide a known voltage at the output while it is in the high-impedance state.

The value of the resistor will depend on multiple factors, including parasitic capacitance and power consumption

limitations. Typically, a 10 kΩ resistor can be used to meet these requirements.

Unused 3-state CMOS outputs should be left disconnected.

8.3.2 CMOS Schmitt-Trigger Inputs

This device includes inputs with the Schmitt-trigger architecture. These inputs are high impedance and are

typically modeled as a resistor in parallel with the input capacitance given in the Electrical Characteristics table

from the input to ground. The worst case resistance is calculated with the maximum input voltage, given in the

Absolute Maximum Ratings table, and the maximum input leakage current, given in the Electrical Characteristics

table, using Ohm's law (R = V ÷ I).

SN74HCS541-Q1

SCLS859 – NOVEMBER 2021

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