SLVSD91D December   2015  – September 2024 TPS562201 , TPS562208

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Adaptive On-Time Control and PWM Operation
      2. 6.3.2 Pulse Skip Control (TPS562201)
      3. 6.3.3 Soft Start and Prebiased Soft Start
      4. 6.3.4 Current Protection
      5. 6.3.5 Undervoltage Lockout (UVLO) Protection
      6. 6.3.6 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Eco-mode Operation
      3. 6.4.3 Standby Operation
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Custom Design with WEBENCH® Tools
        2. 7.2.2.2 Output Voltage Resistors Selection
        3. 7.2.2.3 Output Filter Selection
        4. 7.2.2.4 Input Capacitor Selection
        5. 7.2.2.5 Bootstrap Capacitor Selection
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Custom Design with WEBENCH® Tools
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information
    1. 10.1 Tape and Reel Information

6.3.4 Current Protection

The output overcurrent limit (OCL) is implemented using a cycle-by-cycle valley detect control circuit. The switch current is monitored during the OFF state by measuring the low-side FET drain to source voltage. This voltage is proportional to the switch current. To improve accuracy, the voltage sensing is temperature compensated.

During the on-time of the high-side FET switch, the switch current increases at a linear rate determined by Vin, Vout, the on-time, and the output inductor value. During the on-time of the low-side FET switch, this current decreases linearly. The average value of the switch current is the load current, Iout. If the monitored current is above the OCL level, the converter keeps the low-side FET on and delays the creation of a new set pulse, even the voltage feedback loop requires one, until the current level becomes OCL level or lower. In subsequent switching cycles, the on-time is set to a fixed value and the current is monitored in the same manner.

There are some important considerations for this type of over-current protection. The load current is higher than the overcurrent threshold by one half of the peak-to-peak inductor ripple current. Also, when the current is limited, the output voltage tends to fall as the demanded load current can be higher than the current available from the converter. This can cause the output voltage to fall. When the VFB voltage falls below the UVP threshold voltage, the UVP comparator detects the fall, then the device shuts down after the UVP delay time (typically 256 µs) and restarts after the hiccup time (typically 10 ms).

When the overcurrent condition is removed, the output voltage returns to the regulated value.