SLVSDR8B April   2018  – February 2023 TPS62147 , TPS62148

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  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 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Schematic
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Precise Enable
      2. 9.3.2 Power Good (PG)
      3. 9.3.3 MODE
      4. 9.3.4 Undervoltage Lockout (UVLO)
      5. 9.3.5 Thermal Shutdown
    4. 9.4 Device Functional Modes
      1. 9.4.1 Pulse Width Modulation (PWM) Operation
      2. 9.4.2 Power Save Mode Operation (PWM/PFM)
      3. 9.4.3 100% Duty-Cycle Operation
      4. 9.4.4 Current Limit And Short Circuit Protection (for TPS62148)
      5. 9.4.5 HICCUP Current Limit And Short Circuit Protection (for TPS62147)
      6. 9.4.6 Soft Start / Tracking (SS/TR)
      7. 9.4.7 Output Discharge Function (TPS62148 only)
      8. 9.4.8 Starting into a Pre-Biased Load
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Programming the Output Voltage
      2. 10.1.2 External Component Selection
      3. 10.1.3 Inductor Selection
      4. 10.1.4 Capacitor Selection
        1. 10.1.4.1 Output Capacitor
        2. 10.1.4.2 Input Capacitor
        3. 10.1.4.3 Soft-Start Capacitor
      5. 10.1.5 Tracking Function
      6. 10.1.6 Output Filter and Loop Stability
    2. 10.2 Typical Applications
      1. 10.2.1 Typical Application with Adjustable Output Voltage
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Curves
    3. 10.3 System Examples
      1. 10.3.1 LED Power Supply
      2. 10.3.2 Powering Multiple Loads
      3. 10.3.3 Voltage Tracking
      4. 10.3.4 Precise Soft-Start Timing
    4. 10.4 Power Supply Recommendations
    5. 10.5 Layout
      1. 10.5.1 Layout Guidelines
      2. 10.5.2 Layout Example
      3. 10.5.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

10.3.1 LED Power Supply

The TPS62147, TPS62148 can be used as a power supply for power LEDs. The FB pin can be easily set down to lower values than nominal by using the SS/TR pin. With that, the voltage drop on the sense resistor is low to avoid excessive power loss. Because this pin provides 2.5 µA, the feedback pin voltage can be adjusted by an external resistor per Equation 20. This drop, proportional to the LED current, is used to regulate the output voltage (anode voltage) to a proper level to drive the LED. Both analog and PWM dimming are supported with the TPS62147, TPS62148.

Figure 10-80 shows an application circuit, tested with analog dimming:

GUID-6A9363E8-1E65-43AF-B2A3-1A21465AB491-low.gifFigure 10-80 Single Power LED Supply

The resistor at SS/TR defines the FB voltage. It is set to 350 mV by R5 = 140 kΩ using Equation 20. This cuts the losses on R4 to half from the nominal 0.7 V of feedback voltage while it still provides good accuracy.

Equation 20. GUID-F51E2E9B-F0ED-4590-9F56-D24BB20F3DCA-low.gif

The device supplies a constant current set by resistor R4 from FB to GND. The minimum input voltage has to be rated according the forward voltage needed by the LED used. More information is available in the Application Note SLVA451.