SLVSBD4E May   2012  – September 2021 TPS55340

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 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 Operation
      2. 7.3.2 Switching Frequency
      3. 7.3.3 Overcurrent Protection and Frequency Foldback
        1. 7.3.3.1 Minimum On-Time and Pulse Skipping
      4. 7.3.4 Voltage Reference and Setting Output Voltage
      5. 7.3.5 Soft-Start
      6. 7.3.6 Slope Compensation
      7. 7.3.7 Enable and Thermal Shutdown
      8. 7.3.8 Undervoltage Lockout (UVLO)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation With VIN < 2.9 V (Minimum VIN)
      2. 7.4.2 Operation With EN Control
      3. 7.4.3 Operation at Light Loads
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Boost Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design with WEBENCH Tools
          2. 8.2.1.2.2  Selecting the Switching Frequency (R4)
          3. 8.2.1.2.3  Determining the Duty Cycle
          4. 8.2.1.2.4  Selecting the Inductor (L1)
          5. 8.2.1.2.5  Computing the Maximum Output Current
          6. 8.2.1.2.6  Selecting the Output Capacitors (C8, C9, C10)
          7. 8.2.1.2.7  Selecting the Input Capacitors (C2, C7)
          8. 8.2.1.2.8  Setting Output Voltage (R1, R2)
          9. 8.2.1.2.9  Setting the Soft-start Time (C7)
          10. 8.2.1.2.10 Selecting the Schottky Diode (D1)
          11. 8.2.1.2.11 Compensating the Control Loop (R3, C4, C5)
        3. 8.2.1.3 Application Curves
      2. 8.2.2 SEPIC Converter
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1  Selecting the Switching Frequency (R4)
          2. 8.2.2.2.2  Duty Cycle
          3. 8.2.2.2.3  Selecting the Inductor (L1)
          4. 8.2.2.2.4  Calculating the Maximum Output Current
          5. 8.2.2.2.5  Selecting the Output Capacitors (C8, C9, C10)
          6. 8.2.2.2.6  Selecting the Series Capacitor (C6)
          7. 8.2.2.2.7  Selecting the Input Capacitor (C2, C7)
          8. 8.2.2.2.8  Selecting the Schottky Diode (D1)
          9. 8.2.2.2.9  Setting the Output Voltage (R1, R2)
          10. 8.2.2.2.10 Setting the Soft-start Time (C3)
          11. 8.2.2.2.11 MOSFET Rating Considerations
          12. 8.2.2.2.12 Compensating the Control Loop (R3, C4)
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design with WEBENCH Tools
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.2 Switching Frequency

The switching frequency is set by a resistor (RFREQ) connected to the FREQ pin of the TPS55340. The relationship between the timing resistance RFREQ and frequency is shown in the Figure 6-5. Do not leave this pin open. A resistor must always be connected from the FREQ pin to ground for proper operation. The resistor value required for a desired frequency can be calculated using Equation 1.

Equation 1. RFREQ(kΩ) = 57500 × ƒsw(kHz)–1.03

For the given resistor value, the corresponding frequency can be calculated by Equation 2.

Equation 2. ƒsw(kHz) = 41600 × RFREQ(kΩ)–0.97

The TPS55340 switching frequency can be synchronized to an external clock signal that is applied to the SYNC pin. The required logic levels of the external clock are shown in Section 6.3. The recommended duty cycle of the clock is in the range of 10% to 90%. A resistor must be connected from the FREQ pin to ground when the converter is synchronized to the external clock and the external clock frequency must be within ±20% of the corresponding frequency set by the resistor. For example, if the frequency programmed by the FREQ pin resistor is 600 kHz, the external clock signal should be in the range of 480 kHz to 720 kHz.

With a switching frequency below 280 kHz (typical) after the TPS55340 enters frequency foldback as described in Section 7.3.3, if a load remains when the overcurrent condition is removed, then the output may not recover to the set value. For the output to return to the set value, the load must be removed completely or the TPS55340 power cycled with the EN pin or VIN pin. Select a nominal switching frequency of 350 kHz for quicker recovery from frequency foldback.