SLLSE11H March   2012  – March 2019 SN65HVD72 , SN65HVD75 , SN65HVD78

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Diagram
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics
    6. 7.6  Power Dissipation
    7. 7.7  Switching Characteristics: 250 kbps Device (SN65HVD72) Bit Time ≥ 4 µs
    8. 7.8  Switching Characteristics: 20 Mbps Device (SN65HVD75) Bit Time ≥50 ns
    9. 7.9  Switching Characteristics: 50 Mbps Device (SN65HVD78) Bit Time ≥20 ns
    10. 7.10 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
        1. 10.2.1.1 Data Rate and Bus Length
        2. 10.2.1.2 Stub Length
        3. 10.2.1.3 Bus Loading
        4. 10.2.1.4 Receiver Failsafe
        5. 10.2.1.5 Transient Protection
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 External Transient Protection
        2. 10.2.2.2 Isolated Bus Node Design
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Related Links
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

9.4 Device Functional Modes

When the driver enable pin, DE, is logic high, the differential outputs A and B follow the logic states at data input D. A logic high at D causes A to turn high and B to turn low. In this case the differential output voltage defined as VOD = VA – VB is positive. When D is low, the output states reverse, B turns high, A becomes low, and VOD is negative.

When DE is low, both outputs turn high-impedance. In this condition the logic state at D is irrelevant. The DE pin has an internal pulldown resistor to ground; thus, when left open, the driver is disabled (high-impedance) by default. The D pin has an internal pullup resistor to VCC; thus, when left open while the driver is enabled, output A turns high and B turns low.

Table 1. Driver Function Table

INPUT ENABLE OUTPUTS DESCRIPTION
D DE A B
H H H L Actively drive bus high
L H L H Actively drive bus low
X L Z Z Driver disabled
X OPEN Z Z Driver disabled by default
OPEN H H L Actively drive bus high by default

When the receiver enable pin, RE, is logic low, the receiver is enabled. When the differential input voltage defined as VID = VA – VB is positive and higher than the positive input threshold, VIT+, the receiver output, R, turns high. When VID is negative and lower than the negative input threshold, VIT–, the receiver output turns low. If VID is between VIT+ and VIT–, the output is indeterminate.

When RE is logic high or left open, the receiver output is high-impedance and the magnitude and polarity of VID are irrelevant. Internal biasing of the receiver inputs causes the output to go failsafe-high when the transceiver is disconnected from the bus (open-circuit), the bus lines are shorted (short-circuit), or the bus is not actively driven (idle bus).

Table 2. Receiver Function Table

DIFFERENTIAL INPUT ENABLE OUTPUT DESCRIPTION
VID = VA – VB RE R
VIT+ < VID L H Receive valid bus high
VIT– < VID < VIT+ L ? Indeterminate bus state
VID < VIT– L L Receive valid bus low
X H Z Receiver disabled
X OPEN Z Receiver disabled by default
Open-circuit bus L H Failsafe high output
Short-circuit bus L H Failsafe high output
Idle (terminated) bus L H Failsafe high output
SN65HVD72 SN65HVD75 SN65HVD78 hvd7x_hd_eq_i-o_sche_sllse11.gifFigure 18. Equivalent Input and Output Circuit Diagrams