SLVSGP3A May   2023  – February 2024 TPS54KB20

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  Internal VCC LDO and Using External Bias On the VCC Pin
      2. 6.3.2  Enable
      3. 6.3.3  Adjustable Soft Start
      4. 6.3.4  Power Good
      5. 6.3.5  Output Voltage Setting
      6. 6.3.6  Remote Sense
      7. 6.3.7  D-CAP4 Control
      8. 6.3.8  Multifunction Select (MSEL) Pin
      9. 6.3.9  Low-side MOSFET Zero-Crossing
      10. 6.3.10 Current Sense and Positive Overcurrent Protection
      11. 6.3.11 Low-side MOSFET Negative Current Limit
      12. 6.3.12 Overvoltage and Undervoltage Protection
      13. 6.3.13 Output Voltage Discharge
      14. 6.3.14 UVLO Protection
      15. 6.3.15 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Auto-Skip Eco-mode Light Load Operation
      2. 6.4.2 Forced Continuous-Conduction Mode
      3. 6.4.3 Powering the Device From a Single Bus
      4. 6.4.4 Powering the Device From a Split-rail Configuration
  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  Output Voltage Setting Point
        2. 7.2.2.2  Choose the Switching Frequency and the Operation Mode
        3. 7.2.2.3  Choose the Inductor
        4. 7.2.2.4  Set the Current Limit (ILIM)
        5. 7.2.2.5  Choose the Output Capacitor
        6. 7.2.2.6  RAMP Selection
        7. 7.2.2.7  Choose the Input Capacitors (CIN)
        8. 7.2.2.8  Soft-Start Capacitor (SS Pin)
        9. 7.2.2.9  EN Pin Resistor Divider
        10. 7.2.2.10 VCC Bypass Capacitor
        11. 7.2.2.11 BOOT Capacitor
        12. 7.2.2.12 RC Snubber
        13. 7.2.2.13 PG Pullup Resistor
      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 Documentation Support
      1. 8.1.1 Related Documentation
    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

Package Options

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

6.3.12 Overvoltage and Undervoltage Protection

The device monitors a resistor-divided feedback voltage to detect overvoltage and undervoltage events. The OVP function enables when the output is enabled. The UVP function enables after the soft-start period is complete. The OVP and UVP thresholds given in the following explanation are for the 0.9V reference devices and vary slightly with the 0.5V reference devices. Refer to the Electrical Characteristics in Section 5 for more detailed specifications.

After soft start is complete, if the FB voltage becomes lower than 80% of the VREF voltage, the UVP comparator trips and an internal UVP delay counter begins counting. After the 70µs UVP delay time, depending on the part number, the device either hiccup or latch off. The TPS54KB22 and TPS54KB23 enter hiccup mode and re-start after a sleep time of 7 × the soft-start period. The TPS54KB20 and TPS54KB21 latch off both high-side and low-side MOSFETs drivers. The latch-off fault can be cleared with a reset of VIN or by toggling the EN pin.

When the output is enabled, the FB voltage must rise above the 92.5% PG low-to-high threshold to clear the UVP comparator. If the FB voltage does not exceed the 92.5% threshold by the end of the soft-start period, the device responds to the undervoltage event.

During the UVP delay time, if the FB voltage becomes higher than the 92.5% PG low-to-high threshold, the undervoltage event is cleared and the timer is reset to zero. When the output voltage falls below the 80% UVP threshold again, the 70-μs timer re-starts.

When the FB voltage becomes higher than 118% of the VREF voltage, the OVP comparator trips and the circuit latches the fault condition. The high-side MOSFET turns off and the low-side MOSFET turns on until reaching a negative current limit INOCL. Upon reaching the negative current limit, the low-side MOSFET is turned off, and the high-side MOSFET is turned on again, for a proper on-time (determined by VIN, VOUT, and fSW).. The device operates in this mode until the output voltage is pulled down under the UVP threshold. The device then responds to the undervoltage event as described above. With a short OVP event that is longer than the OVP delay but shorter than the PG high-to-low delay time, the OVP response can trip while PG remains high. In such a scenario, the PG pin pulls low after the output voltage is pulled below the UVP threshold.

If there is an overvoltage condition prior to the output being enabled (such as a high prebiased output), the device responds to the overvoltage event as described above at the beginning of the soft-start period. The OVP threshold is relative to the final VREF voltage, including during the soft-start period. The device waits until the completion of the soft-start period for UVP to be enabled then, depending on the part number, the device either hiccups or latches off in response to the undervoltage event caused by the OVP response. The TPS54KB22 and TPS54KB23 enter hiccup, while the TPS54KB20 and TPS54KB21 latch off.