ZHCSIH1A July   2018  – September 2019 TPS56637

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化原理图
      2.      效率与输出电流间的关系 VOUT = 5V
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling 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  The Adaptive On-Time Control and PWM Operation
      2. 7.3.2  Mode Selection
        1. 7.3.2.1 Eco-mode™ Control Scheme
        2. 7.3.2.2 FCCM Control
      3. 7.3.3  Soft Start and Pre-Biased Soft Start
      4. 7.3.4  Enable and Adjusting Undervoltage Lockout
      5. 7.3.5  Output Overcurrent Limit and Undervoltage Protection
      6. 7.3.6  Overvoltage Protection
      7. 7.3.7  UVLO Protection
      8. 7.3.8  Thermal Shutdown
      9. 7.3.9  Output Voltage Discharge
      10. 7.3.10 Power Good
    4. 7.4 Device Functional Modes
      1. 7.4.1 Standby Operation
      2. 7.4.2 Normal Operation
      3. 7.4.3 Light Load Operation
  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 Output Voltage Resistors Selection
        2. 8.2.2.2 Output Filter Selection
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 Bootstrap Capacitor Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 文档支持
      1. 11.1.1 相关文档
    2. 11.2 接收文档更新通知
    3. 11.3 社区资源
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 Glossary
  12. 12机械、封装和可订购信息
    1. 12.1 Package Option Addendum
      1. 12.1.1 Packaging Information
      2. 12.1.2 Tape and Reel Information

7.3.4 Enable and Adjusting Undervoltage Lockout

The EN pin provides electrical on and off control of the device. When the EN pin voltage exceeds the threshold voltage, the device begins operating. If the EN pin voltage is pulled below the threshold voltage, the regulator stops switching and enters the standby operation.

The EN pin has an internal pull-up current source which allows the user to float the EN pin to enable the device. If an application requires control of the EN pin, open-drain or open-collector output logic can be used to interface with the pin.

The TPS56637 implements internal undervoltage-lockout (UVLO) circuitry on the VIN pin. The device is disabled when the VIN pin voltage falls below the internal VIN UVLO threshold. The internal VIN UVLO threshold has a hysteresis of 500 mV.

If an application requires a higher UVLO threshold on the VIN pin, then the EN pin can be configured as shown in Figure 16. When using the external UVLO function, setting the hysteresis at a value greater than 500 mV is recommended.

The EN pin has a small pull-up current, Ip, which sets the default state of the pin to enable when no external components are connected. The pull-up current is also used to control the voltage hysteresis for the UVLO function because it increases by Ih when the EN pin crosses the enable threshold. Use Equation 2 , and Equation 3 to calculate the values of R1 and R2 for a specified UVLO threshold. Once R1, R2 were settled down, the VEN voltage can be calculated by Equation 4, which should be lower than 5.5V with max VIN.

TPS56637 VinUVLO-slvseg1.gifFigure 16. Adjustable VIN Undervoltage Lockout
Equation 2. TPS56637 equation-2-slvseg1.gif
Equation 3. TPS56637 equation-3-slvseg1.gif
Equation 4. TPS56637 EN-eqution-slvseg1.gif

Where

  • Ip = 1 µA
  • Ih = 4 µA
  • VENfalling = 1.12 V
  • VENrising = 1.18 V
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