SNVSBZ5 March   2021 TPS92360

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Soft Start-Up
      2. 7.3.2 Open LED Protection
      3. 7.3.3 Shutdown
      4. 7.3.4 Current Program
      5. 7.3.5 LED Brightness Dimming
      6. 7.3.6 Undervoltage Lockout
      7. 7.3.7 Thermal Foldback and Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation with CTRL
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Inductor Selection
        2. 8.2.2.2 Schottky Diode Selection
        3. 8.2.2.3 Output Capacitor Selection
        4. 8.2.2.4 LED Current Set Resistor
        5. 8.2.2.5 Thermal Considerations
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
    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

Package Options

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

LED Brightness Dimming

The TPS92360 receives PWM dimming signal at CTRL pin to control the total output current. When the CTRL pin is constantly high, the FB voltage is regulated to 204 mV typically. When the duty cycle of the input PWM signal is low, the regulation voltage at FB pin is reduced, and the total output current is reduced; therefore, it achieves LED brightness dimming. The relationship between the duty cycle and FB regulation voltage is given by:

Equation 2. GUID-C9768BEA-E809-4DF0-871F-A4B5A7EE5837-low.gif

where

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

Thus, the user can easily control the WLED brightness by controlling the duty cycle of the PWM signal.

As shown in Figure 7-1, the IC chops up the internal 204-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 GM 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 filter the PWM signal for analog dimming, TPS92360 regulation voltage is independent of the PWM logic voltage level which often has large variations.

For optimum performance, use the PWM dimming frequency in the range of 5 kHz to 100 kHz. If the PWM frequency is lower than 5 kHz, it is out of the low pass filter's filter range, the FB regulation voltage ripple becomes large, causing large output ripple and may generate audible noise.

GUID-817D301D-C1C2-4D7E-83FE-5F03873C9CBB-low.gifFigure 7-1 Programmable FB Voltage Using PWM Signal