SLVSHL9 November   2024 TPS922051

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Adaptive Off-Time Current Mode Control
      2. 7.3.2 Setting LED Current
      3. 7.3.3 Internal Soft Start
      4. 7.3.4 Dimming Mode
        1. 7.3.4.1 PWM Dimming
        2. 7.3.4.2 Analog Dimming
      5. 7.3.5 Fault Protection
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 TPS922051D2 24V Input, 2A Output, 4-piece WLED Driver With Analog Dimming
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Inductor Selection
          2. 8.2.1.2.2 Input Capacitor Selection
          3. 8.2.1.2.3 Output Capacitor Selection
          4. 8.2.1.2.4 Sense Resistor Selection
          5. 8.2.1.2.5 Other External Components Selection
        3. 8.2.1.3 Application Curves
      2. 8.2.2 TPS922050D1 48V Input, 1A Output, 12-piece WLED Driver with PWM Dimming
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Inductor Selection
          2. 8.2.2.2.2 Input Capacitor Selection
          3. 8.2.2.2.3 Output Capacitor Selection
          4. 8.2.2.2.4 Sense Resistor Selection
          5. 8.2.2.2.5 Other External Components Selection
        3. 8.2.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Package Option Addendum
    2. 11.2 Tape and Reel Information

7.3.1 Adaptive Off-Time Current Mode Control

The TPS922050/1 device adopts an adaptive off-time current mode control to support fast transient response over a wide range of operation. The switching frequency is set at 400kHz or 1MHz.

For average output current regulation, the sensed voltage across the sensing resistor between the CSP and CSN pins is compared with the internal voltage reference, VREF , through the error amplifier. The output of the error amplifier, VCOMP, passes through an external compensation network and is then compared with the peak current feedback at the PWM comparator. During each switching cycle, when the internal NMOS FET is turned on, the peak currernt is sensed through the internal FET. When the sensed value of peak current reaches VCOMP at the input of PWM comparator, the NMOS FET is turned off and the adaptive off-time counter starts counting. Once the adaptive off-time counter stops counting, the counter is reset until when the NMOS FET stays off. The counting off time is determined by the external resistor connected to the FSET pin and the input/output feedforward. Thus, the device is able to maintain a nearly constant switching frequnecy at steady state and regulate the output average current at a desired value.

TPS922050 TPS922051 Adaptive off-time current mode control method Figure 7-1 Adaptive off-time current mode control method