SLVSCU8E August   2015  – November 2017

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 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 GND
      2. 7.3.2 VIN
      3. 7.3.3 dV/dT
      4. 7.3.4 BFET
      5. 7.3.5 EN/UVLO
      6. 7.3.6 ILIM
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Simple 2.1-A eFuse Protection for Set Top Boxes
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Step by Step Design Procedure
          2. 8.2.1.2.2 Programming the Current-Limit Threshold: RILIM Selection
          3. 8.2.1.2.3 Undervoltage Lockout Set Point
          4. 8.2.1.2.4 Setting Output Voltage Ramp Time (TdVdT)
            1. 8.2.1.2.4.1 Case 1: Start-Up without Load: Only Output Capacitance COUT Draws Current During Start-Up
            2. 8.2.1.2.4.2 Case 2: Start-Up with Load: Output Capacitance COUT and Load Draws Current During Start-Up
          5. 8.2.1.2.5 Support Component Selection—CVIN
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Controlled Power Down using TPS25927x
  9. 9 Power Supply Recommendations
    1. 9.1 Transient Protection
    2. 9.2 Output Short-Circuit Measurements
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

9 Power Supply Recommendations

The device is designed for supply voltage range of 4.5 V ≤ VIN ≤ 18 V. If the input supply is located more than a few inches from the device an input ceramic bypass capacitor higher than 0.1 μF is recommended. Power supply must be rated higher than the current limit set to avoid voltage droops during over current and short-circuit conditions.

9.1 Transient Protection

In case of short circuit and over load current limit, when the device interrupts current flow, input inductance generates a positive voltage spike on the input and output inductance generates a negative voltage spike on the output. The peak amplitude of voltage spikes (transients) is dependent on 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:

  • Minimizing lead length and inductance into and out of the device
  • Using large PCB GND plane
  • Schottky diode across the output to absorb negative spikes
  • A low value ceramic capacitor (C(IN) = 0.001 µF to 0.1 µF) to absorb the energy and dampen the transients. The approximate value of input capacitance can be estimated with Equation 18:
Equation 18. TPS259270 TPS259271 eq_43_slvsce9.gif

where

  • V(IN) is the nominal supply voltage
  • I(LOAD) is the load current
  • L(IN) equals the effective inductance seen looking into the source
  • C(IN) 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.

The circuit implementation with optional protection components (a ceramic capacitor, TVS and schottky diode) is shown in Figure 42.

TPS259270 TPS259271 circuit_app_slvscu8.gif Figure 42. Circuit Implementation with Optional Protection Components

9.2 Output Short-Circuit Measurements

It is difficult to obtain repeatable and similar short-circuit testing results. Source bypassing, input leads, circuit layout and component selection, output shorting method, relative location of the short, and instrumentation all contribute to variation in results. The actual short itself exhibits a certain degree of randomness as it microscopically bounces and arcs. Care in configuration and methods must be used to obtain realistic results. Do not expect to see waveforms exactly like those in the data sheet; every setup differs.