ZHCS613A December   2011  – June 2014 TPS22929D

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 简化电路原理图
  5. 5 修订历史记录
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
      1. 7.7.1 Typical AC Characteristics
  8. 8 Parametric Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 On/Off Control
      2. 9.3.2 Output Pull-Down
      3. 9.3.3 Under-Voltage Lockout
      4. 9.3.4 Reverse Current Protection
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 VIN to VOUT Voltage Drop
      2. 10.1.2 Input Capacitor
      3. 10.1.3 Output Capacitor
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Managing Inrush Current
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Thermal Considerations
    2. 12.2 Layout Example
  13. 13器件和文档支持
    1. 13.1 商标
    2. 13.2 静电放电警告
    3. 13.3 术语表
  14. 14机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

10 Application and Implementation

10.1 Application Information

10.1.1 VIN to VOUT Voltage Drop

The VIN to VOUT voltage drop in the device is determined by the RON of the device and the load current. The RON of the device depends upon the VIN condition of the device. Refer to the RON specification of the device in the Electrical Characteristics table of this datasheet. Once the RON of the device is determined based upon the VIN conditions, use Equation 1 to calculate the VIN to VOUT voltage drop:

Equation 1. ΔV = ILOAD × RON

Where,

ΔV = Voltage drop from VIN to VOUT

ILOAD = Load current

RON = On-resistance of the device for a specific VIN

An appropriate ILOAD must be chosen such that the IMAX specification of the device is not violated.

10.1.2 Input Capacitor

To limit the voltage drop on the input supply caused by transient inrush currents, when the switch turns on into a discharged load capacitor or short-circuit, a capacitor needs to be placed between VIN and GND. A 1-μF ceramic capacitor, CIN, placed close to the pins is usually sufficient. Higher values of CIN can be used to further reduce the voltage drop.

10.1.3 Output Capacitor

A CIN to CL ratio of 10 to 1 is recommended for minimizing VIN dip caused by inrush currents during startup.

10.2 Typical Application

TPS22929D typ_app_lvsb39.gif Figure 22. Typical Application Schematic

10.2.1 Design Requirements

Design Parameter Example Value
VIN 1.5 V to 5 V
CL 0.1 µF to 1 µF
Maximum Acceptable Inrush Current 10 mA

10.2.2 Detailed Design Procedure

10.2.2.1 Managing Inrush Current

When the switch is enabled, the output capacitors must be charged up from 0-V to VIN voltage. This charge arrives in the form of inrush current. Inrush current can be calculated using the following equation:

Equation 2. TPS22929D inrush_eq_slvsb49.gif

Where,

C = Output capacitance

TPS22929D dvdt_eq_slvsb49.gif = Output slew rate

The TPS22929D offers a very slow controlled rise time for minimizing inrush current. This device can be selected based upon the maximum acceptable slew rate which can be calculated using the design requirements and the inrush current equation. An output capacitance of 1.0 μF will be used since the amount of inrush increases with output capacitance:

Equation 3. TPS22929D dvdt2_eq_slvsb39.gif
Equation 4. TPS22929D dvdt3_eq_slvsb39.gif

To ensure an inrush current of less than 10 mA, a device with a slew rate less than 10 V/ms must be used.

The TPS22929D has a typical rise time of 4500 μs at 3.3 V . This results in a slew rate of 733 mV/ms which meets the above design requirements.

10.2.3 Application Curves

TPS22929D C018_lvsb39.png
VIN = 5 V TA = 25°C CIN = 10 µF
CL = 1 µF RL = 10 Ω
Figure 23. Turn-On Response
TPS22929D C020_lvsb39.png
VIN = 5 V TA = 25°C CIN = 1 µF
CL = 0.1 µF RL = 10 Ω
Figure 25. Turn-On Response Time
TPS22929D C022_lvsb39.png
VIN = 1.5 V TA = 25°C CIN = 10 µF
CL = 1 µF RL = 10 Ω
Figure 27. Turn-On Response Time
TPS22929D C024_lvsb39.png
VIN = 1.5 V TA = 25°C CIN = 1 µF
CL = 0.1 µF RL = 10 Ω
Figure 29. Turn-On Response Time
TPS22929D C019_lvsb39.png
VIN = 5 V TA = 25°C CIN = 10 µF
CL = 1 µF RL = 10 Ω
Figure 24. Turn-Off Response
TPS22929D C021_lvsb39.png
VIN = 5 V TA = 25°C CIN = 1 µF
CL = 0.1 µF RL = 10 Ω
Figure 26. Turn-Off Response Time
TPS22929D C023_lvsb39.png
VIN = 1.5 V TA = 25°C CIN = 10 µF
CL = 1 µF RL = 10 Ω
Figure 28. Turn-Off Response Time
TPS22929D C025_lvsb39.png
VIN = 1.5 V TA = 25°C CIN = 1 µF
CL = 0.1 µF RL = 10 Ω
Figure 30. Turn-Off Response Time