SLVS827D February   2009  – June 2015 TPS22904

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD 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
  8. 8 Parameter 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
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Input Capacitor (Optional)
      2. 10.1.2 Output Capacitor (Optional)
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 VIN to VOUT Voltage Drop
      3. 10.2.3 Application Curve
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Related Links
    2. 13.2 Community Resources
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, 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

10 Application 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.

10.1 Application Information

10.1.1 Input Capacitor (Optional)

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 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 during high-current application. When switching heavy loads, TI recommends to have an input capacitor about 10 times higher than the output capacitor to avoid excessive voltage drop.

10.1.2 Output Capacitor (Optional)

Due to the integral body diode in the PMOS switch, a CIN greater than CL is highly recommended. 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.

10.2 Typical Application

TPS22903 TPS22904 PMI_lvs827.gifFigure 28. Typical Application Schematic

10.2.1 Design Requirements

Table 2 lists the design parameters for the TPS22903 device.

Table 2. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
VIN 1.8 V
Load Current 0.3 A
Ambient Temperature 25°C

10.2.2 Detailed Design Procedure

10.2.2.1 VIN to VOUT Voltage Drop

The voltage drop from VIN to VOUT is determined by the ON-resistance of the device and the load current. RON can be found in Electrical Characteristics and is dependent on temperature. When the value of RON is found, Equation 1 can be used to calculate the voltage drop across the device:

Equation 1. ΔV = ILOAD × RON

where

  • ΔV = Voltage drop across the device
  • ILOAD = Load current
  • RON = ON-resistance of the device

At VIN = 1.8 V, the TPS22903/4 has an RON value of 90 mΩ. Using this value and the defined load current, the above equation can be evaluated:

Equation 2. ΔV = 0.30 A × 90 mΩ

where

  • ΔV = 27 mV

Therefore, the voltage drop across the device will be 27 mV.

10.2.3 Application Curve

Figure 29 shows the expected voltage drop across the device for different load currents and input voltages.

TPS22903 TPS22904 Vdrop-Graph-TPS22903.gifFigure 29. Voltage Drop vs Load Current