SNVS901A March   2014  – May 2014 TPS92511

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 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  Pulse Level Modulation (PLM) Control
      2. 7.3.2  Pulse Level Modulation (PLM) Operaion Principles
      3. 7.3.3  PLM Control enable Common-Anode Low-Side Sensing (CALS)Technique to Save Wiring
      4. 7.3.4  Internal Regulator
      5. 7.3.5  Setting The Switching Frequency
      6. 7.3.6  Setting The LED Current
      7. 7.3.7  Integrated MOSFET
      8. 7.3.8  Inductor Selection
      9. 7.3.9  Integrated MOSFET Current Limit
      10. 7.3.10 PWM Dimming Control
      11. 7.3.11 Analog Dimming
      12. 7.3.12 High Voltage Buck Configuration
      13. 7.3.13 Thermal Foldback
      14. 7.3.14 EMI Consideration
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation with VIN < 4.5 V (minimum VIN)
      2. 7.4.2 Operation with DIM control
      3. 7.4.3 Linear Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 TPS92511 LED driver for 12 LEDs at 0.5A
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
  9. 9 Power Supply Recommendation
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Thermal Consideration
  11. 11Device and Documentation Support
    1. 11.1 Trademarks
    2. 11.2 Electrostatic Discharge Caution
    3. 11.3 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

8 Application and Implementation

8.1 Application Information

The TPS92511 is an LED driver which provides a regulated output current to drive a single string of LED with the forward voltage lower than the input voltage. The following procedures design a TPS92511 application circuit with an input voltage of 48V, driving an LED string of 38V at an LED current of 0.5A. The switching frequency is 300 kHz.

8.2 Typical Application

8.2.1 TPS92511 LED driver for 12 LEDs at 0.5A

sva30207528_nvs901.gifFigure 23. Application Circuit of TPS92511 (fSW = 300 kHz and ILED = 0.5A)

8.2.1.1 Design Requirements

Table 4. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input voltage range 43V to 53V
LED current 0.5A
LED string forward voltage 38V
Operating frequency 300 kHz

8.2.1.2 Detailed Design Procedure

CIN: The function of the input capacitor CIN is to reduce the input voltage ripple. Ceramic capacitors are recommended owing to the concern of product lifetime. A 100V 2.2 µF ceramic capacitor is selected in this circuit.

CVCC: The capacitor on the VCC pin provides noise filtering and stabilizes the internal regulator. It also prevents false triggering of the VCC UVLO. CVCC is recommended to be a 1 μF good quality and low ESR ceramic capacitor.

D1: The diode D1 should have a reverse voltage larger than VIN in the floating buck topology. In this circuit, a 100V diode is selected.

RFS and RIADJ: In this circuit, the switching frequency and LED current are designed to be 300 kHz and 0.5A. From Table 1 and Table 2, RFS is 33.2 kΩ and RIADJ is 3.01 kΩ.

L1: The selection of inductor mainly affects the inductor current ripple. In this circuit, we design the peak to peak inductor current ripple to be 50% of ILED, i.e. 0.25A. From (6), L1 is calculated to be 106 µH, and a 100 µH inductor is selected.

8.2.1.3 Application Curves

sva30207541_nvs901.png
Figure 24. Efficiency vs VIN
sva30207539_nvs901.gif
Figure 26. Steady State Operation
sva30207516_nvs901.gif
Figure 28. PWM Dimming (VDIM Rising)
sva30207556_nvs901.gif
Figure 30. PWM Dimming (fDIM = 1 kHz, 50% Duty Cycle)
sva30207542_nvs901.png
Figure 25. LED Current Regulation vs VIN
sva30207540_nvs901.gif
Figure 27. Power Up
sva30207517_nvs901.gif
Figure 29. PWM Dimming (VDIM Falling)
sva30207557_nvs901.gif
Figure 31. PWM Dimming (9 µs dimming pulse) (fSW = 500kHz, L1 = 68 µH)