SCLS780C June   2020  – October 2026 SN74HCS266

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
    7. 5.7 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Open-Drain CMOS Outputs
      2. 7.3.2 CMOS Schmitt-Trigger Inputs
      3. 7.3.3 Clamp Diode Structure
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
        1. 8.2.1.1 Power Considerations
        2. 8.2.1.2 Input Considerations
        3. 8.2.1.3 Output Considerations
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Related Links
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.1 Open-Drain CMOS Outputs

Open-drain outputs are included in SN74HCS266. Open-drain outputs can only drive the output low. When in the high logical state, outputs are in a high-impedance state, meaning outputs 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 SN74HCS266 and is dependent on external factors.

Because of the high-impedance state, an external pull-up resistor is required to define a logic high. Without a pull-up resistor, the output floats and has an undefined logic level. The resistor value depends on factors like parasitic capacitance and power consumption; typically, a 10kΩ resistor is suitable.

The drive capability of SN74HCS266 can create fast edges into light loads, so consider routing and load conditions to prevent ringing. Additionally, outputs can drive higher currents than SN74HCS266 is designed to handle continuously. Limit the device output power to avoid damage due to overcurrent. Follow the electrical and thermal limits defined in the Absolute Maximum Ratings at all times. See the Recommended Operating Conditions table for the maximum output voltage that can be externally connected to SN74HCS266.

Leave unused open-drain CMOS outputs disconnected.