JAJSK66A March   2021  – March 2022 TPS2521

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and 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 Switching Characteristics
      1.      15
    8. 7.8 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 Input Reverse Polarity Protection
      2. 8.3.2 Undervoltage Lockout (UVLO and UVP)
      3. 8.3.3 Overvoltage Clamp (OVC)
      4. 8.3.4 Inrush Current, Overcurrent, and Short Circuit Protection
        1. 8.3.4.1 Slew Rate (dVdt) and Inrush Current Control
        2. 8.3.4.2 Active Current Limiting
        3. 8.3.4.3 Short-Circuit Protection
      5. 8.3.5 Analog Load Current Monitor
      6. 8.3.6 Reverse Current Protection
      7. 8.3.7 Overtemperature Protection (OTP)
      8. 8.3.8 Fault Response
      9. 8.3.9 Power Good Indication (PG)
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Single Device, Self-Controlled
    3. 9.3 Typical Application
      1. 9.3.1 Application
      2. 9.3.2 Design Requirements
      3. 9.3.3 Detailed Design Procedure
        1. 9.3.3.1 Device Selection
        2. 9.3.3.2 Setting Undervoltage and Overvoltage Thresholds
        3. 9.3.3.3 Setting Output Voltage Rise Time (tR)
        4. 9.3.3.4 Setting Power Good Assertion Threshold
        5. 9.3.3.5 Setting Overcurrent Threshold (ILIM)
        6. 9.3.3.6 Setting Overcurrent Blanking Interval (tITIMER)
      4. 9.3.4 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Transient Protection
    2. 10.2 Output Short-Circuit Measurements
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 サポート・リソース
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

10.1 Transient Protection

In the case of a short-circuit and overload current limit when the device interrupts current flow, the input inductance generates a positive voltage spike on the input, and the output inductance generates a negative voltage spike on the output. The peak amplitude of voltage spikes (transients) is dependent on the value of inductance in series to the input or output of the device. Such transients can exceed the absolute maximum ratings of the device if steps are not taken to address the issue. Typical methods for addressing transients include:

  • Minimize lead length and inductance into and out of the device.
  • Use a large PCB GND plane.
  • Use a Schottky diode across the output to absorb negative spikes.
  • Connect a low ESR capacitor of value greater than 1 μF at the OUT pin very close to the device.
  • Use a low-value ceramic capacitor CIN = 1 μF to absorb the energy and dampen the transients. The capacitor voltage rating must be at least twice the input supply voltage to be able to withstand the positive voltage excursion during inductive ringing.

The approximate value of input capacitance can be estimated with Equation 15:

Equation 15.

where

  • VIN is the nominal supply voltage.
  • ILOAD is the load current.
  • LIN equals the effective inductance seen looking into the source.
  • CIN is the capacitance present at the input.

Some applications can require the addition of a Transient Voltage Suppressor (TVS) to prevent transients from exceeding the absolute maximum ratings of the device. In some cases, even if the maximum amplitude of the transients is below the absolute maximum rating of the device, a TVS can help to absorb the excessive energy dump and prevent it from creating very fast transient voltages on the input supply pin of the IC, which can couple to the internal control circuits and cause unexpected behavior.

Note: If there is a likelihood of input reverse polarity in the system, TI recommends to use a bi-directional TVS, or a reverse blocking diode in series with the TVS.

For applications such as USB-C ports where a powered cable can be plugged to the output of the device, there can be excess voltage stress from OUT to IN which exceeds the absolute maximum rating of the device. TI recommends to add a TVS diode from OUT to IN to clamp the voltage to a safe level.

The circuit implementation with optional protection components is shown in Figure 10-1.

GUID-20210330-CA0I-96ST-5PCR-84ZS7BLFZSR2-low.gif Figure 10-1 Circuit Implementation with Optional Protection Components