SLDS233B October   2017  – January 2020 TPS92610-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Typical Application Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Timing Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Bias
        1. 7.3.1.1 Power-On Reset (POR)
        2. 7.3.1.2 Low-Quiescent-Current Fault Mode
      2. 7.3.2 Constant-Current Driver
      3. 7.3.3 Device Enable
      4. 7.3.4 PWM Dimming
      5. 7.3.5 Diagnostics
        1. 7.3.5.1 DIAGEN
        2. 7.3.5.2 Low-Dropout Mode
        3. 7.3.5.3 Open-Circuit Detection
        4. 7.3.5.4 Short-to-GND Detection
        5. 7.3.5.5 Single-LED-Short Detection
        6. 7.3.5.6 Overtemperature Protection
      6. 7.3.6 FAULT Bus Output With One-Fails–All-Fail
    4. 7.4 Device Functional Modes
      1. 7.4.1 Undervoltage Lockout, V(SUPPLY)<V(POR_rising)
      2. 7.4.2 Normal Operation V(SUPPLY) ≥ 4.5 V
      3. 7.4.3 Low-Voltage Dropout
      4. 7.4.4 Fault Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Single-Channel LED Driver With Full Diagnostics
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Single-Channel LED Driver With Heat Sharing
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curve
  9. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Community Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.5.5 Single-LED-Short Detection

The TPS92610-Q1 device supports single-LED-short detection by using the SSH and SSL pins. In case there is no need of this feature, SSH and SSL must be tied together to a resistor divider to avoid false alarms as shown in Figure 21.

The TPS92610-Q1 device has integrated a precision comparator to monitor a single-LED-short failure. The comparator uses the bottom LED forward voltage V(SSL) as a reference and monitors the string voltage V(OUT) with resistor divider R1 and R2 at V(SSH).

If a single-LED short is detected, the device turns off the output channel and retries with a small current I(RETRY). Once the fault is removed, the device automatically resumes normal operation.

TPS92610-Q1 SingLEDshort_SLDS233.gifFigure 20. Single-LED Short Detection

Use the following equation to calculate the ratio of R1 and R2.

Equation 2. TPS92610-Q1 eq02-R2value_SLDS233.gif

By using the resistor divider with values calculated in Equation 2, the voltages of SSH and SSL are then equal to the forward voltage of a single LED. With built-in comparators, the device can report failure if any of the LEDs is shorted within this string.

An internal resistor string on SSL and resistors R1 and R2 draw current from OUT. TI recommends total resistance of R1 and R2 greater than 100-kΩ, so the current has negligible effect on LED luminance.

Even within the same batch of LEDs, the LED forward voltage may vary from one to another. Taking account of forward voltage differences is necessary to avoid any false faults.

TPS92610-Q1 single-LED-short-bypass-SLDS233.gifFigure 21. Bypass Single-LED Short Detection
TPS92610-Q1 first-page-schematic-SLDS233.gifFigure 22. With Single-LED Short Detection