ZHCSGY7B October   2017  – January 2018 TPS92830-Q1

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     简化原理图
  4. 4 修订历史记录
  5. 5 说明 （续）
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 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 Device Bias
        1. 8.3.1.1 Power-On-Reset (POR)
        2. 8.3.1.2 Current Reference (IREF)
        3. 8.3.1.3 Low-Current Fault Mode
      2. 8.3.2 Charge Pump
        1. 8.3.2.1 Charge Pump Architecture
      3. 8.3.3 Constant-Current Driving
        1. 8.3.3.1 High-Side Current Sense
        2. 8.3.3.2 High-Side Current Driving
        3. 8.3.3.3 Gate Overdrive Voltage Protection
        4. 8.3.3.4 High-Precision Current Regulation
        5. 8.3.3.5 Parallel MOSFET Driving
      4. 8.3.4 PWM Dimming
        1. 8.3.4.1 Supply Dimming
        2. 8.3.4.2 PWM Dimming by Input
        3. 8.3.4.3 Internal Precision PWM Generator
        4. 8.3.4.4 Full Duty-Cycle Switch
      5. 8.3.5 Analog Dimming
        1. 8.3.5.1 Analog Dimming Topology
        2. 8.3.5.2 Internal High-Precision Pullup Current Source
      6. 8.3.6 Output Current Derating
        1. 8.3.6.1 Output-Current Derating Topology
      7. 8.3.7 Diagnostics and Fault
        1. 8.3.7.1 LED Short-to-GND Detection
        2. 8.3.7.2 LED Short-to-GND Auto Retry
        3. 8.3.7.3 LED Open-Circuit Detection
        4. 8.3.7.4 LED Open-Circuit Auto Retry
        5. 8.3.7.5 Dropout-Mode Diagnostics
        6. 8.3.7.6 Overtemperature Protection
        7. 8.3.7.7 FAULT Bus Output With One-Fails–All-Fail
        8. 8.3.7.8 Fault Table
    4. 8.4 Device Functional Modes
      1. 8.4.1 Undervoltage Lockout, V(IN) < V(UVLO)
      2. 8.4.2 Normal Operation (V(IN) ≥ 4.5 V, V(IN) > V(LED) + 0.5 V)
      3. 8.4.3 Low-Voltage Dropout
      4. 8.4.4 Fault Mode (Fault Is Detected)
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Typical Application for Automotive Exterior Lighting With One-Fails–All-Fail
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 High-Precision Dual-Brightness PWM Generation
        1. 9.2.2.1 Dual-Brightness Application
        2. 9.2.2.2 Design Requirements
        3. 9.2.2.3 Detailed Design Procedure
        4. 9.2.2.4 Application Curve
      3. 9.2.3 Driving High-Current LEDs With Parallel MOSFETs
        1. 9.2.3.1 Application Curves
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 接收文档更新通知
    2. 11.2 社区资源
    3. 11.3 商标
    4. 11.4 静电放电警告
    5. 11.5 Glossary
  12. 12机械、封装和可订购信息

9.2.1.2 Detailed Design Procedure

Fixed Parameters

  • Charge pump flying capacitor C6 = 10 nF
  • Charge pump flying capacitor C8 = 10 nF
  • R(IREF) = 8 kΩ
  • Charge pump storage capacitor C10 = 150 nF

Current Setting

  • I(LED) = 300 mA
  • R(SNS)= V(CS_REG) / I(LED) = 0.983 Ω

PWM Threshold Setting

  • PWM enables when V(IN)> 6 V
  • K(RES_PWM) = VIH(PWMx, max) / 6 V
  • K(RES_PWM) = R15 / (R15 + R8)
  • Set R15 = 20 kΩ, R8 = 76 kΩ

DiagEN Setting (Enables LED-Open Detection When V(IN)> 9 V

  • K(RES_DiagEN) = VIH(DIAGEN, max) / 9 V
  • K(RES_DiagEn) = R13 / (R6 + R13)
  • Set R13 = 10 kΩ, R6 = 62 kΩDiagEN setting

DERATE Setting (Reduces Current Output When V(IN) > 18 V

  • K(RES_DERATE) = V(DERATE_FULL, min) / 18 V
  • K(RES_DERATE) = R7 / (R7+ R14)
  • Set R7 = 10 kΩ, R14 = 95 kΩ

To deliver 300 mA with a single MOSFET package, the designer must consider the maximum thermal-dissipation condition. The power dissipation of a MOSFET is usually at its peak when input voltage is at 16 V in a full-brightness condition. Assume the minimal LED forward voltage at 300 mA is 6 V.

Equation 10. TPS92830-Q1 eq09-Pmosfet_SLIS178.gif

MOSFET package and layout design must be considered to dissipate 2.702 W at maximum ambient temperature, usually 85°C.

The TPS92830 device can support a variety of N-channel MOSFETs in the markets. Adding a capacitor between the gate and source increases the loop phase margin. The recommended total capacitance at Gx is greater than 4 nF.