ZHCSMX7A August   2021  – December 2021 TPS92519-Q1

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Buck Converter Switching Operation
      2. 7.3.2  Switching Frequency and Adaptive On-Time Control
      3. 7.3.3  Minimum On-Time, Off-Time, and Inductor Ripple
      4. 7.3.4  Enable
      5. 7.3.5  LED Current Regulation and Error Amplifier
      6. 7.3.6  Start-up Sequence
      7. 7.3.7  Analog Dimming and Forced Continuous Conduction Mode
      8. 7.3.8  External PWM Dimming and Input Undervoltage Lockout (UVLO)
      9. 7.3.9  Shunt FET Dimming or Matrix Beam Application
      10. 7.3.10 Bias Supply
      11. 7.3.11 Bootstrap Supply
      12. 7.3.12 Faults and Diagnostics
      13. 7.3.13 Output Short Circuit Fault
      14. 7.3.14 Output Open Circuit Fault
      15. 7.3.15 Parallel Operation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power On Reset (POR)
      2. 7.4.2 Run Mode
      3. 7.4.3 Sleep Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Duty Cycle Consideration
      2. 8.1.2  Switching Frequency Selection
      3. 8.1.3  LED Current Set Point
      4. 8.1.4  Inductor Selection
      5. 8.1.5  Output Capacitor Selection
      6. 8.1.6  Input Capacitor Selection
      7. 8.1.7  Bootstrap Capacitor Selection
      8. 8.1.8  Compensation Capacitor Selection
      9. 8.1.9  Input Undervoltage Protection
      10. 8.1.10 CSN Protection Diode
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Calculating Duty Cycle
        2. 8.2.2.2 Calculating Minimum On-Time and Off-Time
        3. 8.2.2.3 Minimum Switching Frequency
        4. 8.2.2.4 LED Current Set Point
        5. 8.2.2.5 Inductor Selection
        6. 8.2.2.6 Output Capacitor Selection
        7. 8.2.2.7 Bootstrap Capacitor Selection
        8. 8.2.2.8 Compensation Capacitor Selection
        9. 8.2.2.9 PWM Dimming and Input Voltage Protection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Compact Layout for EMI Reduction
        1. 10.1.1.1 Ground Plane
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 支持资源
    4. 11.4 Trademarks
    5. 11.5 术语表
  12. 12Mechanical, Packaging, and Orderable Information

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7.3.5 LED Current Regulation and Error Amplifier

The reference voltage, VIADJ, is internally scaled by a gain factor of 1/14 through a resistor network. An internal rail-to-rail error amplifier generates an error signal proportional to the difference between the scaled reference voltage (VIADJ / 14) and the inductor current measured by the differential voltage drop between CSP and CSN, V(CSP-CSN). This error drives the COMP pin voltage, VCOMP, and directly controls the valley threshold of the inductor current. Zero average DC error and closed-loop regulation is achieved by implementing an integral compensation network consisting of a capacitor connected from the output of the error amplifier to GND. As a good starting point, TI recommends a capacitor value between 1 nF and 10 nF between the COMP pin and GND. The choice of compensation network must ensure a minimum of 60° of phase margin and 10 dB of gain margin. The Application and Implementation section summarizes the detailed design procedure.

GUID-20210314-CA0I-9J8H-HLCT-NPNZC7JGZ1H2-low.gif Figure 7-2 Closed-loop LED Current Regulation

LED current is dependent on the current sense resistor, RCS. Use Equation 6 to calculate the LED current.

Equation 6. GUID-20210314-CA0I-QVLC-XM63-0ZPRL9BGF5GZ-low.gif

LED current accuracy is a function of the tolerance of the external sense resistor, RCS, and the variation in the sense threshold, V(CSP-CSN), caused by internal mismatch and temperature dependency of the analog components. The TPS92519-Q1 is capable of achieving LED current accuracy of ±4% at full scale over common-mode range and a junction temperature range of –40°C to 150°C.