SLVSBD8A April   2014  – May 2014 TPS62095

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 Handling Ratings
    3. 6.3 Recommend 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 PWM Operation
      2. 7.3.2 Low Dropout Operation (100% Duty Cycle)
      3. 7.3.3 Power Save Mode Operation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Soft Startup
      2. 7.4.2 Voltage Tracking
      3. 7.4.3 Short Circuit Protection (Hiccup-Mode)
      4. 7.4.4 Output Discharge Function
      5. 7.4.5 Power Good Output
      6. 7.4.6 Undervoltage Lockout
      7. 7.4.7 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 2.5V to 5.5V Input, 1.8V Output Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Output Filter
          2. 8.2.1.2.2 Inductor Selection
          3. 8.2.1.2.3 Input and Output Capacitor Selection
          4. 8.2.1.2.4 Setting the Output Voltage
        3. 8.2.1.3 Application Performance Curves
      2. 8.2.2 2.5V to 5.5V Input, 1.2V Output Converter
      3. 8.2.3 3.0V to 5.5V Input, 2.6V Output Converter
      4. 8.2.4 5V Input, 3.3V Output Converter
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Consideration
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, 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

8 Application and Implementation

8.1 Application Information

The TPS62095 is a synchronous step down converter based on DCS-Control™ topology whose output voltage can be adjusted by component selection. The following section discusses the design of the external components to complete the power supply design for several input and output voltage options by using typical applications as a reference.

8.2 Typical Applications

8.2.1 2.5V to 5.5V Input, 1.8V Output Converter

typ_app_lvsbd8.gifFigure 7. 1.8-V Output Application

8.2.1.1 Design Requirements

For this design example, use the following as the input parameters.

Table 1. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input voltage range 2.5V to 5.5V
Output voltage 1.8V
Output ripple voltage <20mV
Output current rating 4A

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Output Filter

The first step is the selection of the output filter components. To simplify this process, Table 2 outlines possible inductor and capacitor value combinations.

Table 2. Output Filter Selection

INDUCTOR VALUE [µH](3) OUTPUT CAPACITOR VALUE [µF](2)
10 22 2 x 22 100 150
0.47 √ √ √
1.0 √(1) √ √
2.2
(1) Typical application configuration. Other check mark indicates alternative filter combinations
(2) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by +20% and –50%.
(3) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by +20% and –30%.

8.2.1.2.2 Inductor Selection

The inductor selection is affected by several parameters like inductor ripple current, output voltage ripple, transition point into Power Save Mode, and efficiency. See Table 3 for typical inductors.

Table 3. Inductor Selection(1)

INDUCTOR VALUE COMPONENT SUPPLIER SIZE (LxWxH mm) Isat / DCR
1 µH Coilcraft XAL4020-102 4.0 x 4.0 x 2.1 8.75A / 13.2 mΩ
0.47 µH TOKO DFE322512C 3.2 x 2.5 x 1.2 5.9A / 21 mΩ

In addition, the inductor has to be rated for the appropriate saturation current and DC resistance (DCR). The inductor needs to be rated for a saturation current as high as the typical switch current limit of 5.5A or according to Equation 6 and Equation 7. Equation 6 and Equation 7 calculate the maximum inductor current under static load conditions. The formula takes the converter efficiency into account. The converter efficiency can be taken from the data sheet graphs or 80% can be used as a conservative approach. The calculation must be done for the maximum input voltage where the peak switch current is highest.

Equation 6. eq_IL_slvsaw2.gif
Equation 7. eq_IL_2_slvsaw2.gif

where


ƒ = Converter switching frequency (typically 1.4MHz)
L = Inductor value
η = Estimated converter efficiency (use the number from the efficiency curves or 0.80 as a conservative assumption)

Note: The calculation must be done for the maximum input voltage of the application

Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation current. A margin of 20% should be added to cover for load transients during operation.

8.2.1.2.3 Input and Output Capacitor Selection

For best output and input voltage filtering, low ESR ceramic capacitors are recommended. The input capacitor minimizes input voltage ripple, suppresses input voltage spikes and provides a stable system rail for the device. A 22µF or larger input capacitor is required. The output capacitor value can range from 2x22µF up to 150µF. The recommended typical output capacitor value is 2x22µF and can vary over a wide range as outline in the output filter selection table.

8.2.1.2.4 Setting the Output Voltage

The output voltage is set by an external resistor divider according to the following equations:

Equation 8. EQ2_vout_lvsaw2.gif
Equation 9. EQ3_R2_lvsaw2.gif
Equation 10. EQ4_R1_lvsaw2.gif

When sizing R2, in order to achieve low quiescent current and acceptable noise sensitivity, use a minimum of 5µA for the feedback current IFB. Larger currents through R2 improve noise sensitivity and output voltage accuracy.

8.2.1.3 Application Performance Curves

TA = 25°C, VIN = 3.6V, VOUT = 1.8V, L1 = 1µH (XAL4020-102), C2 = 2x22µF, unless otherwise noted.

D001_SLVSBD8_TPS62095.gif
Figure 8. Efficiency, VOUT = 1.8V
D007_SLVSBD8_TPS62095.gif
Figure 10. Line Regulation, VOUT = 1.8V, IOUT = 1.0A
D009_SLVSBD8_TPS62095.gif
Figure 12. Output Ripple, VOUT = 1.8V, IOUT = 100mA
D002_SLVSBD8_TPS62095.gif
Figure 9. Load Regulation, VOUT = 1.8V, VIN = 3.3V
D008_SLVSBD8_TPS62095.gif
Figure 11. Switching Frequency, VOUT = 1.8V
D010_SLVSBD8_TPS62095.gif
Figure 13. Output Ripple, VOUT = 1.8V, IOUT = 3.5A
D011_SLVSBD8_TPS62095.gif
Figure 14. Startup, Relative to VIN, RLOAD = 1.5Ω
D013_SLVSBD8_TPS62095.gif
Figure 16. Load Transient, VOUT = 1.8V
D015_SLVSBD8_TPS62095.gif
Figure 18. Short Circuit, HICCUP Protection Entry
D012_SLVSBD8_TPS62095.gif
Figure 15. Startup, Relative to EN, RLOAD = 1.5Ω
D014_SLVSBD8_TPS62095.gif
Figure 17. Load Transient, VOUT = 1.8V
D016_SLVSBD8_TPS62095.gif
Figure 19. Short Circuit, HICCUP Protection Exit

8.2.2 2.5V to 5.5V Input, 1.2V Output Converter

1p2_app_lvsbd8.gif
Figure 20. 1.2V Output Application
D017_SLVSBD8_TPS62095.gifFigure 21. 1.2V Output Application Efficiency

8.2.3 3.0V to 5.5V Input, 2.6V Output Converter

2p6_app_lvsbd8.gif
Figure 22. 2.6V Output Application
D018_SLVSBD8_TPS62095.gifFigure 23. 2.6V Output Application Efficiency

8.2.4 5V Input, 3.3V Output Converter

3p3_app_lvsbd8.gif
Figure 24. 3.3V Output Application
D019_SLVSBD8_TPS62095.gif
Figure 25. 3.3V Output Application Efficiency