SLVSET0E May   2020  – October 2024 TPS61378-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  VCC Power Supply
      2. 7.3.2  Input Undervoltage Lockout (UVLO)
      3. 7.3.3  Enable and Soft Start
      4. 7.3.4  Shut Down
      5. 7.3.5  Switching Frequency Setting
      6. 7.3.6  Spread Spectrum Frequency Modulation
      7. 7.3.7  Adjustable Peak Current Limit
      8. 7.3.8  Bootstrap
      9. 7.3.9  Load Disconnect
      10. 7.3.10 MODE/SYNC Configuration
      11. 7.3.11 Overvoltage Protection (OVP)
      12. 7.3.12 Output Short Protection/Hiccup
      13. 7.3.13 Power-Good Indicator
      14. 7.3.14 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Forced PWM Mode
      2. 7.4.2 Auto PFM Mode
      3. 7.4.3 External Clock Synchronization
      4. 7.4.4 Down Mode
  9. 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 Programming the Output Voltage
        2. 8.2.2.2 Setting the Switching Frequency
        3. 8.2.2.3 Setting the Current Limit
        4. 8.2.2.4 Selecting the Inductor
        5. 8.2.2.5 Selecting the Output Capacitors
        6. 8.2.2.6 Selecting the Input Capacitors
        7. 8.2.2.7 Loop Stability and Compensation
          1. 8.2.2.7.1 Small Signal Model
          2. 8.2.2.7.2 Loop Compensation Design Steps
          3. 8.2.2.7.3 Selecting the Bootstrap Capacitor
          4. 8.2.2.7.4 VCC Capacitor
      3. 8.2.3 Application Curves
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Glossary
    6. 11.6 Electrostatic Discharge Caution
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

8.2.2.1 Programming the Output Voltage

The output voltage is determined by the resistor sensed from FB pin before device is enabled.

There are two ways to set the output voltage of the TPS61378-Q1, adjustable output voltage(for TPS61378-Q1 and TPS613783-Q1 only) and fixed output voltage.

TPS61378-Q1 Typical Connection of FB Pin For Adjustable Output Voltage Figure 8-2 Typical Connection of FB Pin For Adjustable Output Voltage
Figure 8-2 shows the typical circuit of the FB pin conncetion for adjustable output voltage. The FB resistor RFB is defined as Equation 3:
Equation 3. R F B = R I N S E R T + R U P × R D O W N R U P + R D O W N
When selected for adjustable output voltage, RFB must be above 14.4kΩ. The FB pin is connected to the negative input of the internal error amplifier directly. The output voltage can be programmed by adjusting the external resistor divider RUP and RDOWN according to Equation 4.
Equation 4. V O U T = V R E F × ( R U P + R D O W N ) R D O W N

Equation 4 shows that the output voltage setting is only influenced by RUP and RDOWN. In normal application, RINSERT can be 0Ω, that is, directly connect FB pin to middle point of feedback voltage divider.

For automotive application that do not prefer to use resistors more than 100 kΩ, RINSERT (>15kΩ) can be used so that calculated RUP and RDOWN feedback resistor value could be less than 100kΩ.

When working with adjustable voltage, for the best accuracy, RDOWN is recommended to be smaller than 160 kΩ to ensure that the current flowing through RDOWN is at least 100 times larger than FB pin leakage current. Changing RDOWN towards the lower value increases the robustness against noise injection. Changing RDOWN to higher values reduces the quiescent current to achieve higher efficiency at light load.

TPS61378-Q1 Typical Connection of FB Pin For Fixed Output Voltage Figure 8-3 Typical Connection of FB Pin For Fixed Output Voltage

Figure 8-3 shows the typical circuit of the FB pin conncetion for fixed output voltage.The FB resistor RFB is defined as Equation 5:

Equation 5. R F B = R D O W N
When designed for fixed output voltage, the TPS61378-Q1 uses the internal resistor divider and works with fixed output voltage. The TPS61378-Q1 subdivides the voltage due to RFB and device part number. See Device Comparison Table for detailed information.