SLVSAD4B August   2010  – April 2015 TPS22934

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  Switching Characteristics: VIN = 3.6 V
    7. 6.7  Switching Characteristics: VIN = 2.5 V
    8. 6.8  Switching Characteristics: VIN = 1.8 V
    9. 6.9  Switching Characteristics: VIN = 1.5 V
    10. 6.10 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 ON and OFF Control
      2. 8.3.2 Undervoltage Lockout
      3. 8.3.3 Quick Output Discharge
    4. 8.4 Device Functional Modes
  9. 9 Applications and Implementation
    1. 9.1 Application Information
      1. 9.1.1 VIN to VOUT Voltage Drop
      2. 9.1.2 Input Capacitor
      3. 9.1.3 Output Capacitor
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Input Capacitor
        2. 9.2.2.2 Output Capacitor
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, 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 Applications and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The TPS22934 device is a single channel, 1-A load switch supporting VIN in the range of 1.5 to 3.6 V. The ON pin controls the state of the switch. ON pin voltage can be between 0 and 3.6 V. The device has built-in hysteresis on its control input. The load switch is active when ON voltage is greater than the positive going voltage threshold (VTH+). If the ON voltage is lower than the negative going voltage threshold (VTH-), then the pass FET is deactivated and the active pulldown from VOUT to GND is activated.

9.1.1 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 data sheet. 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.

9.1.2 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.

9.1.3 Output Capacitor

TI recommends a CIN to CL ratio of 10 to 1 for minimizing VIN dip caused by inrush currents during start-up.

9.2 Typical Application

Figure 30 demonstrates how the TPS22934 can be used for power-rail sequencing.

TPS22934 ai_power_rail_sequencing_2_lvsad4.gifFigure 30. 1.8-V and 2.8-V Power-Rail Sequencing

9.2.1 Design Requirements

Table 4. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
VREG1 1.8 V
VREG2 2.8 V

9.2.2 Detailed Design Procedure

9.2.2.1 Input Capacitor

To limit the voltage drop on the input supply caused by transient in-rush currents when the switch turns on into a discharged load capacitor or short-circuit, a capacitor must 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. A CIN to CL ratio of 10 to 1 is recommended.

9.2.2.2 Output Capacitor

Due to the integral body diode in the PMOS switch, TI highly recommends a CIN greater than CL. A CL greater than CIN can cause VOUT to exceed VIN when the system supply is removed. This could result in current flow through the body diode from VOUT to VIN.

9.2.3 Application Curve

TPS22934 TPS22934.pngFigure 31. Power-Rail Sequencing of 2.8-V and 1.8-V Rail