SLVS790E November   2007  – April 2019 TPS61165

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
  4. 4 Revision History
  5. 5 Device Options
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Recommended Operating Conditions
    3. 7.3 Thermal Information
    4. 7.4 Electrical Characteristics
    5. 7.5 Timing Requirements
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Soft Start-Up
      2. 8.3.2 Open LED Protection
      3. 8.3.3 Undervoltage Lockout
      4. 8.3.4 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Maximum Output Current
      2. 9.1.2 Inductor Selection
      3. 9.1.3 Schottky Diode Selection
      4. 9.1.4 Compensation Capacitor Selection
      5. 9.1.5 Input and Output Capacitor Selection
    2. 9.2 Typical Applications
      1. 9.2.1 TPS61165 Typical Application
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 LED Brightness Dimming Mode Selection
          2. 9.2.1.2.2 PWM Brightness Dimming
          3. 9.2.1.2.3 Digital One-Wire Brightness Dimming
          4. 9.2.1.2.4 EasyScale: One-Wire Digital Dimming
          5. 9.2.1.2.5 Current Program
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Additional Application Circuits
    3. 9.3 Do's and Don'ts
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.1.2.2 PWM Brightness Dimming

When the CTRL pin is constantly high, the FB voltage is regulated to 200 mV typically. However, the CTRL pin allows a PWM signal to reduce this regulation voltage; therefore, it achieves LED brightness dimming. The relationship between the duty cycle and FB voltage is shown in Equation 6.

Equation 6. VFB = Duty × 200 mV

where

  • Duty = duty cycle of the PWM signal
  • 200 mV = internal reference voltage

As shown in Figure 10, the device chops up the internal 200-mV reference voltage at the duty cycle of the PWM signal. The pulse signal is then filtered by an internal low pass filter. The output of the filter is connected to the error amplifier as the reference voltage for the FB pin regulation. Therefore, although a PWM signal is used for brightness dimming, only the WLED DC current is modulated, which is often referred as analog dimming. This eliminates the audible noise which often occurs when the LED current is pulsed in replica of the frequency and duty cycle of PWM control. Unlike other methods which filters the PWM signal for analog dimming, TPS61165 regulation voltage is independent of the PWM logic voltage level which often has large variations.

TPS61165 fb_v_bd_lvs790.gifFigure 10. Block Diagram of Programmable FB Voltage Using PWM Signal

For optimum performance, use the PWM dimming frequency in the range of 6.5 kHz to 100 kHz. The requirement of minimum dimming frequency comes from the EasyScale detection delay and detection time specification in the dimming mode selection. Because the CTRL pin is logic only pin, adding an external RC filter applied to the pin does not work.

To use lower PWM dimming, add external RC network connected to the FB pin as shown in Additional Application Circuits.