SLVS861F august   2008  – june 2020 TPS40210-Q1 , TPS40211-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     4
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 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  Minimum On-Time and Off-Time Considerations
      2. 7.3.2  Current Sense and Overcurrent
      3. 7.3.3  Current Sense and Subharmonic Instability
      4. 7.3.4  Current Sense Filtering
      5. 7.3.5  Soft Start
      6. 7.3.6  BP Regulator
      7. 7.3.7  Shutdown (DIS/ EN Pin)
      8. 7.3.8  Control Loop Considerations
      9. 7.3.9  Gate Drive Circuit
      10. 7.3.10 TPS40211-Q1
    4. 7.4 Device Functional Modes
      1. 7.4.1 Setting the Oscillator Frequency
      2. 7.4.2 Synchronizing the Oscillator
  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  Duty Cycle Estimation
        2. 8.2.2.2  Inductor Selection
        3. 8.2.2.3  Rectifier Diode Selection
        4. 8.2.2.4  Output Capacitor Selection
        5. 8.2.2.5  Input Capacitor Selection
        6. 8.2.2.6  Current Sense and Current Limit
        7. 8.2.2.7  Current Sense Filter
        8. 8.2.2.8  Switching MOSFET Selection
        9. 8.2.2.9  Feedback Divider Resistors
        10. 8.2.2.10 Error Amplifier Compensation
        11. 8.2.2.11 R-C Oscillator
        12. 8.2.2.12 Soft-Start Capacitor
        13. 8.2.2.13 Regulator Bypass
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Support Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1.     69

8.2.2.10 Error Amplifier Compensation

While current mode control typically requires only Type II compensation, it is desirable to layout for Type III compensation to increase flexibility during design and development.

Current mode control boost converters have higher gain with higher output impedance, so it is necessary to calculate the control loop gain at the maximum output impedance, estimated by Equation 57.

Equation 57. GUID-BBF8F037-C4DA-4991-BA20-FD54B68F78F3-low.gif

The transconductance of the TPS40210-Q1 current-mode control can be estimated by Equation 58.

Equation 58. GUID-90FC57DB-2AA3-47D7-BE41-D51544D5598D-low.gif

The maximum output impedance, ZOUT, can be estimated by Equation 59.

Equation 59. GUID-AC25DE79-FCF6-420F-83F1-7627B9665C1B-low.gif
Equation 60. GUID-13E3925C-D561-44E4-94DC-BDAEB0D208F6-low.gif

The modulator gain at the desired cross-over can be estimated by Equation 61.

Equation 61. GUID-7D5F9D1A-ABDD-4A2A-97D9-200CC9FD2EE9-low.gif

The feedback compensation network needs to be designed to provide an inverse gain at the cross-over frequency for unit loop gain. This sets the compensation mid-band gain at a value calculated in Equation 62.

Equation 62. GUID-0514E67A-1BE8-4E44-8EFA-77366B33E014-low.gif

To set the mid-band gain of the error amplifier to KCOMP, use Equation 63.

Equation 63. GUID-6527342C-E8D6-4263-BCA0-42EA2F40B5D1-low.gif

R4 = 18.7 kΩ selected.

Place the zero at one 10th of the desired cross-over frequency.

Equation 64. GUID-6FC81615-75F2-464E-99FC-D12E6E70B271-low.gif

C2 = 2200 pF selected.

Place a high-frequency pole at about five times the desired cross-over frequency and less than one-half the unity gain bandwidth of the error amplifier:

Equation 65. GUID-0523E28A-068E-4E76-9F02-969A933CD7D3-low.gif
Equation 66. GUID-2DDD5CD0-D240-4837-9030-19EF420D4B74-low.gif

C4 = 47 pF selected.