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

8.2.2.2 Detailed Design Procedure

Using parallel resistors, thermal performance can be improved by balancing current between the TPS92610-Q1 device and the external resistors as follows. As the current-sense resistor controls the total LED string current, the LED string current I(LED) is set by V(CS_REG) / R(SNS), while the TPS92610-Q1 current I(DRIVE) and parallel resistor current I(P) combine to the total current.

Note that the parallel resistor path cannot be shut down by PWM or fault protection. If PWM or one-fails–all-fail feature is required, TI recommends an application circuit as described in Single-Channel LED Driver With Full Diagnostics.

In linear LED driver applications, the input voltage variation contributes to most of the thermal concerns. The resistor current, as indicated by Ohm’s law, depends on the voltage across the external resistors. The TPS92610-Q1 controls the driver current I(DRIVE) to attain the desired total current. If I(P) increases, the TPS92610-Q1 device decreases I(DRIVE) to compensate, and vice versa.

While in low-dropout mode, the voltage across the R(P) resistor may be close to zero, so that almost no current can flow through the external resistor R(P).

When the input voltage is high, the parallel-resistor current I(P) is proportional to the voltage across the parallel resistor R(P). The parallel resistor R(P) takes the majority of the total string current, generating maximum heat. The device must prevent current from draining out to ensure current regulation capability.

In this case, the parallel resistor value must be carefully calculated to ensure that 1) enough output current is achieved in low-dropout mode, 2) thermal dissipation for both the TPS92610-Q1 device and the resistor is within their thermal dissipation limits, and 3) device current in the high-voltage mode is above the minimal output-current requirement.

Current setting by sense resistor is as described in Equation 7.

Equation 7. TPS92610-Q1 eq07-Rsns2_SLDS233.gif

LED-string maximum forward voltage = 3 × 2.5 V = 7.5 V.

Parallel resistor R(P) is recommended to consume 50% of the total current at maximum supply voltage.

Equation 8. TPS92610-Q1 eq08-Rp_SLDS233.gif

Total device power consumption is maximum at 16 V input and LED minimal forward voltage.

Equation 9. TPS92610-Q1 eq09-Pdevmax_SLDS233.gif

Resistor R(P) maximum power consumption is at 16-V input.

Equation 10. TPS92610-Q1 eq-10-PRPMAX.gif

Users must consider the maximum power of both of the device and the parallel resistor.