SLUSAE6B December   2010  – November 2023 TPS53315

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  D-CAP™ Integrated Circuit with Adaptive On-Time
      2. 6.3.2  Small Signal Model
      3. 6.3.3  Ramp Signal
      4. 6.3.4  Auto-Skip Eco-mode Light Load Operation
      5. 6.3.5  Adaptive Zero Crossing
      6. 6.3.6  Forced Continuous Conduction Mode
      7. 6.3.7  Power Good
      8. 6.3.8  Current Sense and Overcurrent Protection
      9. 6.3.9  Overvoltage and Undervoltage Protection
      10. 6.3.10 UVLO Protection
      11. 6.3.11 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Enable and Soft Start
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Typical Application Circuit Diagram
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Step 1: Select Operation Mode and Soft-Start Time
          2. 7.2.1.2.2 Step 2: Select Switching Frequency
          3. 7.2.1.2.3 Step 3: Select the Inductance
          4. 7.2.1.2.4 Step 4: Select Output Capacitors
          5. 7.2.1.2.5 Step 5: Determine the Voltage-Divider Resistance (R1 and R2)
          6. 7.2.1.2.6 Step 6: Select the Overcurrent Resistance (RTRIP)
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Typical Application Circuit Diagram With Ceramic Output Capacitors
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
          1. 7.2.2.2.1 Step 1: Select Operation Mode and Soft-Start Time
          2. 7.2.2.2.2 Step 2: Select Switching Frequency
          3. 7.2.2.2.3 Step 3: Select the Inductance
          4. 7.2.2.2.4 Step 4: Select Output Capacitance for Ceramic Capacitors
          5. 7.2.2.2.5 Step 5: Select the Overcurrent Setting Resistance (RTRIP)
        3. 7.2.2.3 External Component Selection When Using All Ceramic Output Capacitors
        4. 7.2.2.4 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
        1. 7.4.2.1 Thermal Considerations
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6.3.2 Small Signal Model

From small-signal loop analysis, a buck converter using D-CAP integrated circuit can be simplified as shown in Figure 6-3.

GUID-A148345B-B494-47CA-AFCE-36659F4D29D8-low.gifFigure 6-3 Simplified Modulator Model

The output voltage is compared with the internal reference voltage (ramp signal is ignored here for simplicity). The PWM comparator determines the timing to turn on the high-side MOSFET. The gain and speed of the comparator can be assumed high enough to keep the voltage at the beginning of each on-cycle substantially constant.

Equation 1. GUID-E54BD9A7-F220-4292-BCC1-AA51E23C051E-low.gif

For the loop stability, the 0 dB frequency, ƒ0, defined in Equation 2 must be lower than ¼ of the switching frequency.

Equation 2. GUID-E46076AD-84ED-4B51-A193-A7160E7A1744-low.gif

According to Equation 2, the loop stability of D-CAP integrated circuit modulator is mainly determined by the capacitor chemistry. For example, specialty polymer capacitors (SP-CAP) have COUT on the order of several 100 µF and ESR in range of 10 mΩ. These makes ƒ0 on the order of 100 kHz or less and the loop is stable. However, ceramic capacitors have an ƒ0 at more than 700 kHz, and need special care when used with this modulator. An application circuit using ceramic capacitors is described in Section 7.2.2.3 section.