SLLS550E November   2002  – March 2023 SN65HVD08 , SN75HVD08

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Driver Switching Characteristics
    7. 6.7 Receiver Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Supply Source Impedance
      2. 9.1.2 Opto-Isolated Data Buses
      3. 9.1.3 Opto Alternative
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 Data Rate and Bus Length
        2. 9.2.1.2 Stub Length
          1.        30
          2.        31
        3. 9.2.1.3 Bus Loading
        4. 9.2.1.4 Receiver Failsafe
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.1.1 Supply Source Impedance

In the steady state, the voltage drop from the source to the load is simply the wire resistance times the load current as modeled in Figure 9-1.

GUID-05D318BE-E92B-49CC-82D5-8AE7B3D9CEAD-low.gifFigure 9-1 Steady-State Circuit Model

For example, if you were to provide 5-V ±5% supply power to a remote circuit with a maximum load requirement of 0.1 A (one SN65HVD08), the voltage at the load would fall below the 4.5-V minimum of most 5-V circuits with as little as 5.8 m of 28-GA conductors. Table 9-1 summarizes wire resistance and the length for 4.5 V and 3 V at the load with 0.1 A of load current. The maximum lengths would scale linearly for higher or lower load currents.

Table 9-1 Maximum Cable Lengths for Minimum Load Voltages at 0.1 A Load
WIRE SIZERESISTANCE4.5-V LENGTH
AT 0.1 A		3-V LENGTH
AT 0.1 A
28 Gauge0.213 Ω/m5.8 m41.1 m
24 Gauge0.079 Ω/m15.8 m110.7 m
22 Gauge0.054 Ω/m23.1 m162.0 m
20 Gauge0.034 Ω/m36.8 m257.3 m
18 Gauge0.021 Ω/m59.5 m416.7 m

Under dynamic load requirements, the distributed inductance and capacitance of the power lines may not be ignored and decoupling capacitance at the load is required. The amount depends upon the magnitude and frequency of the load current change but, if only powering the SN65HVD08, a 0.1 µF ceramic capacitor is usually sufficient.