SLUSED1B May   2020  – June 2021 TPS543820

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 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  VIN Pins and VIN UVLO
      2. 7.3.2  Enable and Adjustable UVLO
      3. 7.3.3  Adjusting the Output Voltage
      4. 7.3.4  Switching Frequency Selection
      5. 7.3.5  Switching Frequency Synchronization to an External Clock
        1. 7.3.5.1 Internal PWM Oscillator Frequency
        2. 7.3.5.2 Loss of Synchronization
        3. 7.3.5.3 Interfacing the SYNC/FSEL Pin
      6. 7.3.6  Ramp Amplitude Selection
      7. 7.3.7  Soft Start and Prebiased Output Start-up
      8. 7.3.8  Mode Pin
      9. 7.3.9  Power Good (PGOOD)
      10. 7.3.10 Current Protection
        1. 7.3.10.1 Positive Inductor Current Protection
        2. 7.3.10.2 Negative Inductor Current Protection
      11. 7.3.11 Output Overvoltage and Undervoltage Protection
      12. 7.3.12 Overtemperature Protection
      13. 7.3.13 Output Voltage Discharge
    4. 7.4 Device Functional Modes
      1. 7.4.1 Forced Continuous-Conduction Mode
      2. 7.4.2 Discontinuous Conduction Mode during Soft Start
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 1.0-V Output, 1-MHz Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Switching Frequency
          2. 8.2.1.2.2  Output Inductor Selection
          3. 8.2.1.2.3  Output Capacitor
          4. 8.2.1.2.4  Input Capacitor
          5. 8.2.1.2.5  Adjustable Undervoltage Lockout
          6. 8.2.1.2.6  Output Voltage Resistors Selection
          7. 8.2.1.2.7  Bootstrap Capacitor Selection
          8. 8.2.1.2.8  BP5 Capacitor Selection
          9. 8.2.1.2.9  PGOOD Pullup Resistor
          10. 8.2.1.2.10 Current Limit Selection
          11. 8.2.1.2.11 Soft-Start Time Selection
          12. 8.2.1.2.12 Ramp Selection and Control Loop Stability
          13. 8.2.1.2.13 MODE Pin
        3. 8.2.1.3 Application Curves
      2. 8.2.2 1.0-V Output, 1.5-MHz Application
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3 3.3-V Output, 1.0-MHz Application
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Thermal Performance
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.10.1 Positive Inductor Current Protection

The current is sensed in the high-side MOSFET while it is conducting after a short blanking time to allow noise to settle. Whenever the high-side overcurrent threshold is exceeded, the high-side MOSFET is immediately turned off and the low-side MOSFET is turned on. The high-side MOSFET does not turn back on until the current falls below the low-side MOSFET overcurrent threshold. This effectively limits the peak current in the case of a short circuit condition. If a high-side overcurrent is detected for 15 consecutive cycles, the device enters hiccup.

The current is also sensed in the low-side MOSFET while it is conducting after a short blanking time to allow noise to settle. If the low-side overcurrent threshold is exceeded when the next incoming PWM signal is received from the controller, the device skips processing that PWM pulse. The device does not turn the high-side MOSFET on again until the low-side overcurrent threshold is no longer exceeded. If the low-side overcurrent threshold remains exceeded for 15 consecutive cycles, the device enters hiccup. There are two separate counters for the high-side and low-side overcurrent events. If the off-time is too short, the low-side overcurrent may not trip. The low-side overcurrent will, however, begin tripping after the high-side peak overcurrent limit is hit as hitting the peak current limit shortens the on-time and lengthens the off-time.

Both the high-side and low-side positive overcurrent thresholds are programmable using the MODE pin. Two sets of thresholds are available ("High" and "Low"), which are summarized in Table 7-5. The values for these thresholds are obtained using open-loop measurements with a DC current in order to accurately specify the values. In real applications, the inductor current will ramp and the ramp rate will be a function of the voltage across the inductor (VIN - VOUT) as well as the inductance value. This ramp rate combined with delays in the current sense circuitry can result in slightly different values than specified. The current at which the high-side overcurrent limit takes effect can be slightly higher than specified, and the current at which the low-side overcurrent limit takes effect can be slightly lower than specified.

Table 7-5 Overcurrent Thresholds
MODE PIN CURRENT LIMIT SETTINGHIGH-SIDE OVERCURRENT TYPICAL VALUE (A)LOW-SIDE OVERCURRENT TYPICAL VALUE (A)
High

12.2

10.4

Low

9.0

7.4