SLVSD01B September   2015  – May 2019 TPS57140-EP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      Efficiency vs Load Current
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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  Fixed Frequency PWM Control
      2. 7.3.2  Slope-Compensation Output Current
      3. 7.3.3  Bootstrap Voltage (Boot)
      4. 7.3.4  Low-Dropout Operation
      5. 7.3.5  Error Amplifier
      6. 7.3.6  Voltage Reference
      7. 7.3.7  Adjusting the Output Voltage
      8. 7.3.8  Enable and Adjusting UVLO
      9. 7.3.9  Slow-Start or Tracking Pin (SS/TR)
      10. 7.3.10 Overload Recovery Circuit
      11. 7.3.11 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
      12. 7.3.12 Overcurrent Protection and Frequency Shift
      13. 7.3.13 Selecting the Switching Frequency
      14. 7.3.14 How to Interface to RT/CLK Pin
      15. 7.3.15 Power Good (PWRGD Pin)
      16. 7.3.16 Overvoltage Transient Protection (OVTP)
      17. 7.3.17 Thermal Shutdown
      18. 7.3.18 Small-Signal Model for Loop Response
      19. 7.3.19 Simple Small-Signal Model for Peak-Current-Mode Control
      20. 7.3.20 Small-Signal Model for Frequency Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Sequencing
      2. 7.4.2 Pulse-Skip Eco-mode Control Scheme
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Selecting the Switching Frequency
        2. 8.2.2.2  Output Inductor Selection (LO)
        3. 8.2.2.3  Output Capacitor
        4. 8.2.2.4  Catch Diode
        5. 8.2.2.5  Input Capacitor
        6. 8.2.2.6  Slow-Start Capacitor
        7. 8.2.2.7  Bootstrap Capacitor Selection
        8. 8.2.2.8  UVLO Set Point
        9. 8.2.2.9  Output Voltage and Feedback Resistors Selection
        10. 8.2.2.10 Compensation
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Power-Dissipation Estimate
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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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

7.3.8 Enable and Adjusting UVLO

The VIN pin voltage falling below 2.5 V disables the TPS57140-EP. If an application requires a higher UVLO, use the EN pin as shown in Figure 28 to adjust the input-voltage UVLO by using two external resistors. Though it is not necessary to use the UVLO adjust resistors, for operation, TI highly recommends providing consistent power-up behavior. The EN pin has an internal pullup current source, I1, of 0.9 μA that provides the default condition of the TPS57140-EP operating when the EN pin floats. When the EN pin voltage exceeds 1.25 V, an additional 2.9 μA of hysteresis, Ihys, is added. This additional current facilitates input-voltage hysteresis. Use Equation 2 to set the external hysteresis for the input voltage. Use Equation 3 to set the input start voltage.

TPS57140-EP v_lockout_lvsd01.gifFigure 28. Adjustable UVLO
Equation 2. TPS57140-EP q_r1_lvs795.gif
Equation 3. TPS57140-EP q_r2_lvs795.gif

Figure 29 shows another technique to add input-voltage hysteresis. The designer can use this method if the resistance values are high from the previous method and there is a need for a wider voltage hysteresis. Resistor R3 sources additional hysteresis current into the EN pin.

TPS57140-EP add_hys_lvsd01.gifFigure 29. Adding Additional Hysteresis
Equation 4. TPS57140-EP q_r1hyst_lvs795.gif
Equation 5. TPS57140-EP q_r2hyst_lvs795.gif

Do not place a low-impedance voltage source with >5 V directly on the EN pin. Do not place a capacitor directly on the EN pin if VEN > 5 V when using a voltage divider to adjust the start and stop voltage. The node voltage (see Figure 30) must remain ≤5.8 V. The Zener diode can sink up to 100 μA. The EN pin voltage can be >5 V if the VIN voltage source has a high impedance and does not source more than 100 μA into the EN pin.

TPS57140-EP v10065_lvs795.gifFigure 30. Node Voltage