SNOSDC0A October   2020  – December 2020 LM7310

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 Timing Requirements
    7. 6.7 Switching Characteristics
    8.     14
    9. 6.8 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 Input Reverse Polarity Protection
      2. 7.3.2 Undervoltage Protection (UVLO & UVP)
      3. 7.3.3 Overvoltage Lockout (OVLO)
      4. 7.3.4 Inrush Current control and Fast-trip
        1. 7.3.4.1 Slew Rate (dVdt) and Inrush Current Control
        2. 7.3.4.2 Fast-Trip During Steady State
      5. 7.3.5 Analog Load Current Monitor Output
      6. 7.3.6 Reverse Current Protection
      7. 7.3.7 Overtemperature Protection (OTP)
      8. 7.3.8 Fault Response
      9. 7.3.9 Power Good Indication (PG)
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Single Device, Self-Controlled
      1. 8.2.1 Typical Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Setting Undervoltage and Overvoltage Thresholds
          2. 8.2.1.2.2 Setting Output Voltage Rise Time (tR)
          3. 8.2.1.2.3 Setting Power Good Assertion Threshold
          4. 8.2.1.2.4 Setting Analog Current Monitor Voltage (IMON) Range
        3. 8.2.1.3 Application Curves
    3. 8.3 Active ORing
    4. 8.4 Priority Power MUXing
    5. 8.5 USB PD Port Protection
    6. 8.6 Parallel Operation
  9. 9 Power Supply Recommendations
    1. 9.1 Transient Protection
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

9.1 Transient Protection

When the device interrupts current flow in the case of a fast-trip event or during normal switch off, 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.
  • Connect a Schottky diode from the OUT pin ground 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 should be atleast 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. GUID-20200925-CA0I-9DP5-D7QV-VWC61486KC9G-low.gif

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 may 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's a likelihood of input reverse polarity in the system, it's recommended to use a bi-directional TVS, or a reverse blocking diode in series with the TVS.

The circuit implementation with optional protection components is shown in Figure 9-1.

GUID-20200919-CA0I-MJGJ-VVZM-VC0JD1GS3SRM-low.gif Figure 9-1 Circuit Implementation with Optional Protection Components