SNLS141E August   2002  – March 2024 DS90LT012A , DS90LV012A

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Description
  4. 3 Pin Configuration and Functions
  5. 4 Specifications
    1. 4.1 Absolute Maximum Ratings
    2. 4.2 Recommended Operating Conditions
    3. 4.3 Electrical Characteristics
    4. 4.4 Switching Characteristics
  6. 5 Parameter Measurement Information
  7. 6 Detailed Description
    1. 6.1 Functional Block Diagram
    2. 6.2 Feature Description
      1. 6.2.1 Termination
      2. 6.2.2 Threshold
      3. 6.2.3 Fail-Safe Feature
      4. 6.2.4 Probing LVDS Transmission Lines
    3. 6.3 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
  9. 8 Power Supply Recommendations
  10. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Differential Traces
    3. 9.3 Cables and Connectors, General Comments
  11. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

6.2.2 Threshold

The LVDS Standard (ANSI/TIA/EIA-644-A) specifies a maximum threshold of ±100mV for the LVDS receiver. The DS90LV012A and DS90LT012A support an enhanced threshold region of −100mV to 0V. This is useful for fail-safe biasing. The threshold region is shown in the Voltage Transfer Curve (VTC) in Figure 6-3. The typical DS90LV012A or DS90LT012A LVDS receiver switches at about −30mV. Note that with VID = 0V, the output will be in a HIGH state. With an external fail-safe bias of +25mV applied, the typical differential noise margin is now the difference from the switch point to the bias point. In the example below, this would be 55mV of Differential Noise Margin (+25mV − (−30mV)). With the enhanced threshold region of −100mV to 0V, this small external fail-safe biasing of +25mV (with respect to 0V) gives a DNM of a comfortable 55mV. With the standard threshold region of ±100mV, the external fail-safe biasing would need to be +25mV with respect to +100mV or +125mV, giving a DNM of 155mV which is stronger fail-safe biasing than is necessary for the DS90LV012A or DS90LT012A. If more DNM is required, then a stronger fail-safe bias point can be set by changing resistor values.

DS90LT012A DS90LV012A VTC of the DS90LV012A and DS90LT012A LVDS ReceiversFigure 6-3 VTC of the DS90LV012A and DS90LT012A LVDS Receivers