SLLSEI2A September   2017  – December 2017 SN55HVD233-SP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and 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  Driver Electrical Characteristics
    6. 7.6  Receiver Electrical Characteristics
    7. 7.7  Driver Switching Characteristics
    8. 7.8  Receiver Switching Characteristics
    9. 7.9  Device Switching Characteristics
    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
      1. 9.3.1 Modes
      2. 9.3.2 Loopback
      3. 9.3.3 CAN Bus States
      4. 9.3.4 ISO 11898 Compliance of SN55HVD233-SP
        1. 9.3.4.1 Introduction
        2. 9.3.4.2 Differential Signal
          1. 9.3.4.2.1 Common-Mode Signal
        3. 9.3.4.3 Interoperability of 3.3-V CAN in 5-V CAN Systems
      5. 9.3.5 Thermal Shutdown
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Diagnostic Loopback
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Slope Control
        2. 10.2.2.2 Standby
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Bus Loading, Length, and Number of Nodes
      2. 12.1.2 CAN Termination
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Receiving Notification of Documentation Updates
    2. 13.2 Community Resources
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • HKX|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

12 Layout

12.1 Layout Guidelines

Minimize stub length from node insertion to bus.

12.1.1 Bus Loading, Length, and Number of Nodes

The ISO11898 standard specifies up to 1-Mbps data rate, maximum bus length of 40 m, maximum drop line (stub) length of 0.3 m, and a maximum of 30 nodes. However, with careful network design, the system may have longer cables, longer stub lengths, and many more nodes to a bus. Many CAN organizations and standards have scaled the use of CAN for applications outside the original ISO11898 standard. They made system level trade-offs for data rate, cable length, and parasitic loading of the bus. Examples of some of these specifications are ARINC825, CANopen, CAN Kingdom, DeviceNet, and NMEA200.

A high number of nodes requires a transceiver with high input impedance and wide common mode range such as the SN55HVD233-SP CAN. ISO11898-2 specifies the driver differential output with a 60-Ω load (two 120-Ω termination resistors in parallel), and the differential output must be greater than 1.5 V. The SN55HVD233-SP is specified to meet the 1.5-V requirement with a 60-Ω load, and additionally specified with a differential output voltage minimum of 1.2 V across a common mode range of –2 to 7 V through a 330-Ω coupling network. This network represents the bus loading of 120 SN55HVD233-SP transceivers based on their minimum differential input resistance of 40 kΩ. Therefore, the SN55HVD233-SP supports up to 120 transceivers on a single bus segment with margin to the 1.2-V minimum differential input voltage requirement at each node. For CAN network design, margin must be given for signal loss across the system and cabling, parasitic loadings, network imbalances, ground offsets, and signal integrity; thus, a practical maximum number of nodes may be lower. Bus length may also be extended beyond the original ISO11898 standard of 40 m by careful system design and data rate tradeoffs. For example, CANopen network design guidelines allow the network to be up to 1 km with changes in the termination resistance, cabling, less than 64 nodes, and significantly lowered data rate.

This flexibility in CAN network design is one of the key strengths of the various extensions and additional standards that have been built on the original ISO11898 CAN standard. Using this flexibility requires good network design.

12.1.2 CAN Termination

The ISO11898 standard specifies the interconnect to be a twisted pair cable (shielded or unshielded) with 120-Ω characteristic impedance (ZO). Use resistors equal to the characteristic impedance of the line to terminate both ends of the cable to prevent signal reflections. Keep unterminated drop lines (stubs) connecting nodes to the bus as short as possible to minimize signal reflections. The termination may be on the cable or in a node, but if nodes may be removed from the bus, the termination must be carefully placed so that it is not removed from the bus.

SN55HVD233-SP typ_CAN_bus_llsea2.gif Figure 33. Typical CAN Bus

Termination is typically a 120-Ω resistor at each end of the bus. If filtering and stabilization of the common mode voltage of the bus is desired, then the user may use split termination (see Figure 34). Split termination uses two 60-Ω resistors with a capacitor in the middle of these resistors to ground. Split termination improves the electromagnetic emissions behavior of the network by eliminating fluctuations in the bus common mode voltages at the start and end of message transmissions.

Take care with the power ratings of the termination resistors used, especially for the worst-case condition (if a system power supply is shorted across the termination resistance to ground). In most cases, under the worst-case condition, much higher current passes through the termination resistance than the CAN transceiver's current limit.

SN55HVD233-SP CAN_bus_term_llsea2.gif Figure 34. CAN Bus Termination Concepts

12.2 Layout Example

SN55HVD233-SP sn55hvd233-layout-example-block-diagram.gif Figure 35. Board Layout Example